Potential of New Plant Sources as Raw Materials for Obtaining Natural Pigments/Dyes

Abstract

Natural dyes can be extracted from fruits, flowers, leaves, and roots. Exploring new sources of natural dyes, especially from underutilized plants, emerges as a promising strategy. The main advantages of exploiting unconventional plants include local availability, specialty food production, cultural significance, sustainable production, technological feasibility, and new fundamental insights. Finding and exploiting such underutilized plants is significant as unfavorable climatic and human conditions put natural vegetation at risk worldwide. Thus, this study aims to review plants with potential applications as natural dyes and pigments, highlighting their potential applications, benefits, and prospects. An integrative review was conducted by searching Web of Science, ScienceDirect, and SpringerLink for all studies published up to December 2024. For this review, a total of 133 references that presented the information and data of interest to the authors were selected. This review highlighted their potential applications in food, cosmetic, pharmaceutical, and textile industries. Despite the growing interest in natural dyes, challenges related to their stability, seasonality, and extraction efficiency continue to limit their commercial use. However, advancements in extraction technologies have improved the applicability of these compounds. Additionally, utilizing underexplored plant sources presents a strategic opportunity to diversify dye production, reduce reliance on traditional sources, and promote more sustainable practices.

1. Introduction

The use of plants as natural colorants holds a rich and enduring history across diverse cultures, where specific species have been essential for dyeing textiles, food, and various materials. The use of these colorants can be traced back to ancient civilizations, as seen in the exquisite mural paintings of Ajanta, Ellora, Sithannavasal, and Mithila, as well as the Egyptian pyramids, all crafted exclusively with natural pigments. In Europe, prehistoric art from the Altamira and El Castillo caves in Spain and the Niaux caves in the French Pyrenees highlights the extensive use of mineral pigments like ferric oxide (red), ferrous oxide (yellow), and copper carbonate (blue). The ancient Vedas also document the primary dyeing colors—red, yellow, blue, black, and white—and describe how craftsmen derived these hues from natural sources: indigo for blue, turmeric and saffron for yellow, cutch for brown, and lac, safflower, and madder for red. These practices demonstrate the profound role natural dyes have played in human history, shaping art, culture, and daily life for millennia [1].

Ethnobotanical studies reveal that traditional dyeing practices are deeply rooted in cultural identity and heritage. For example, the Baiku Yao community in China uses plants like Ailanthus vilmoriniana to dye their traditional garments, underscoring the cultural significance of these natural resources in their textile traditions [2]. Similarly, in Madagascar, indigenous plants are prized for their unique dyeing properties, which remain central to local artisanal techniques [3]. In Northern Thailand, communities have developed intricate methods to extract vibrant dyes from a variety of plants for use in silk, wool, and cotton textiles, showcasing the impressive diversity of plant-based pigments [4].

Color plays an essential role in the sensory perception of products, often being the first attribute influencing consumer acceptance [5]. In food, colors not only provide visual appeal but also serve as indicators of freshness, quality, and flavor [6]. Historically, natural pigments have been widely used to dye food, textiles, and cosmetics. However, the advent of synthetic dyes during the industrial era transformed the market by offering a wide range of colors, greater stability, and reduced costs [7].

Beyond their visual appeal, natural pigments, such as anthocyanins, carotenoids, betalains, and chlorophylls, among others, are beneficial to health, exhibiting antioxidant, anti-inflammatory, anticancer, and even antiallergic properties. These attributes make them promising compounds for the prevention of chronic diseases and the promotion of well-being [5,8]. The versatility of these compounds is also reflected in their origins; natural dyes can be extracted from various parts of plants, such as fruits, peels, flowers, stems, roots, and seeds, significantly expanding the range of available sources for the sustainable production of pigments [7,8].

On the other hand, synthetic dyes, widely used for their stability and low cost, have been associated with various health risks, including allergic reactions, toxic effects, and even long-term carcinogenicity [6,9]. These concerns, along with the rising demand for natural ingredients, have led to the replacement of artificial dyes with safer, more sustainable natural alternatives. This shift is driven by growing consumer interest in healthier food options and environmentally friendly practices [6]. However, natural dyes still face challenges, including chemical instability when exposed to factors like light, heat, and oxygen, as well as issues related to cost and the seasonal availability of raw materials [5].

In recent years, the development of green extraction and stabilization technologies has played a crucial role in overcoming these limitations. Methods such as ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), and supercritical fluid extraction (SFE) are known for their efficiency, sustainability, and ability to preserve the bioactive properties of pigments. Among other promising techniques, these approaches minimize the use of toxic solvents, increase process yields, and optimize the final quality of extracted compounds [10,11]. Furthermore, encapsulation techniques have been extensively utilized to protect pigments from adverse factors and enhance their stability in industrial applications, thereby expanding their potential use in a variety of food matrices [6].

Another significant advancement is the use of natural dyes in intelligent packaging. These materials can act as indicators of food freshness or expiration, changing color in response to temperature, pH, or microbiological spoilage variations. This innovation not only helps extend the shelf life of food but also promotes sustainability by reducing food waste [12,13].

In this context, exploring new sources of natural dyes, especially from underutilized plants, emerges as a promising strategy. The main advantages of exploring unconventional plants include local availability, the production of specialty foods, cultural significance, sustainable production, technological feasibility, and new fundamental insights. Finding and exploiting these underutilized plants is significant, as unfavorable climatic and human conditions put natural vegetation at risk worldwide. Alternative plant resources and the rediscovery of underutilized plants should be prioritized in the search for important natural dyes [8,14].

Given the above, Unconventional Food Plants (UFPs) can be explored for this purpose, with an emphasis on flowers, fruits, leaves, and roots. UFPs refer to edible parts of exotic or native plants that are absent from people’s dietary habits and/or are produced and traded outside traditional food systems. These species have great nutritional value and can also play an important role in social, financial, and environmental spheres. Despite this, there are still gaps in the literature on the different possibilities and potential applications of these plants [15].

These plants have great potential to be applied as natural food dyes, offering an excellent alternative to synthetic dyes, but studies on this subject are still scarce. Thus, this study aims to review plants with potential applications as natural dyes and pigments, highlighting their potential applications, benefits, and prospects.

2. Data Source

To select the species described in this review, literature searches were carried out to verify which Unconventional Food Plants could present a potential dye (colored vegetables) and which of these were still little explored for this purpose. And, based on the results found, we selected the species for this review.

An integrative review was conducted by searching Web of Science, ScienceDirect, and SpringerLink for all studies published up to December 2024. The searches were performed in the databases using the following strategy for each plant: Composition OR Dye OR Dyes OR Pigment) AND scientific name (

Table 1. Search strategy of Web of Science, SpringerLink, and ScienceDirect.

First Part of the Search		Second Part of the Search
(Composition OR Dye OR Colorants OR Pigment)	AND	Xanthosoma riedelianum Schott
		Alpinia officinarum Hance
		Dioscorea trifida L.f.
		Tropaeolum majus L.
		Bougainvillea glabra Choisy
		Clitoria ternatea L.
		Cosmos bipinnatus Cav.
		Impatiens balsamina L.
		Sonchus oleraceus L.
		Basella rubra L.
		Hibiscus sabdariffa L.
		Celosia argentea L. Rubus rosifolius Sm.
		Syzygium jambos (L.) Alston
		Solanum betaceum Cav.
		Clidemia hirta (L.) D. Don
		Genipa americana L.
		Eugenia brasiliensis Lam.

). The inclusion criteria were articles published between 2014 and 2024, original articles, and book chapters with full access, while the exclusion criteria were articles that did not meet the inclusion criteria mentioned above, as well as repeated publications and articles outside the scope of this work (

Table 2. Number of scientific articles retrieved with the search strategy.

Vegetable	Database
	ScienceDirect	SpringerLink	Web of Science
Xanthosoma riedelianum Schott	0	0	0
Alpinia officinarum Hance	129	0	18
Dioscorea trifida L.f.	55	0	6
Tropaeolum majus L.	208	123	26
Bougainvillea glabra Choisy	183	79	37
Clitoria ternatea L.	501	224	98
Cosmos bipinnatus Cav.	65	50	12
Impatiens balsamina L.	155	122	18
Sonchus oleraceus L.	326	250	42
Basella rubra L.	154	154	23
Hibiscus sabdariffa L.	11	11	220
Celosia argentea L. Rubus rosifolius Sm.	88	88	20
	228	657	0
Syzygium jambos (L.) Alston	246	140	41
Solanum betaceum Cav.	72	34	31
Clidemia hirta (L.) D. Don	63	47	15
Genipa americana L.	249	100	46
Eugenia brasiliensis Lam.	208	126	22

). For this review, a total of 133 references that presented the information and data of interest to the authors were selected.

3. Vegetables with Dye Potential

Plants are the most important sources of natural dyes and exhibit various colors, such as red, yellow, blue, black, brown, and their combinations. Almost all parts of plants produce dyes, be they the root, stem, bark, leaves, flowers, fruits, seeds, or wood. Around 500 species of plants have been identified as potential sources of dye, and it is estimated that their various parts synthesize more than 2000 pigments. Many plant pigments are used as dyes. Madder has been utilized since times as a red vegetable dye for leather, wool, cotton, and silk. Indigo is a natural dye that is structurally related to betalains. Tyrian purple, which is an ancient dye, has been extracted from shellfish of the Murex genus. However, only around 150 have been commercially explored (affron, pomegranate rind, turmeric, bugloss, bloodroot) [16]. Factors such as the quality or origin of the raw material, harvesting time, pre-treatments, and the operational conditions used in extraction directly affect the characteristics of the pigments [17]. Among the main obstacles to the production of natural dyes are the dependence on raw materials and the variation in the pigments extracted, making it extremely important to identify new plant raw materials with the potential for dye extraction.

3.1. Roots

The use of unconventional roots to extract compounds to act as dyes is still limited. Few species are being evaluated in the literature, which highlights an area for investigation. Among the species of roots with potential for use as dyes are Dioscorea spp., Alpinia officinarum Hance, and Xanthosoma riedelianum Schoth (Figure 1).

3.1.1. Dioscorea spp.

Yams are plant species of the Dioscoreaceae family and Dioscorea genus that have edible tubers. These foods have an attractive nutritional profile and bioactive properties, such as antibacterial, antioxidant, and anti-inflammatory properties. Due to these properties, most studies focus on evaluating nutritional and technofunctional characteristics [18]. However, the potential of some species, such as D. alata L. and D. trifida, allows for their application as dyes, since they present characteristic pigments. In purple-colored Dioscorea spp. cultivars, anthocyanins are the responsible antioxidant pigments, while in yellow-colored cultivars, carotenoids are present [19]. In purple-colored cultivars, different anthocyanins are found, such as cyanidin 3-gentiobioside, allatanin C, cyanidin 3-ferulyl gentiobioside, cyanidin 3-sinapilgentianoside, peonidin 3-gentiobioside, and allatanin 2 [20].

The by-products of yam species that present pigmentation can be flour and starch. Flour is obtained by grinding the edible portion of the yam and subsequently drying at 105 °C. To extract the starch, previous steps of cleaning, peeling, and cutting into smaller pieces are necessary, followed by homogenization in various solvents, such as water, an alkaline solution, or a sodium bisulfite solution. Next, filtration and centrifugation steps are carried out, and the final precipitate is then dried in an oven or freeze-dried.

Some pigments can be transported to starch during its extraction. Starches that present pigmentation can be applied in product formulation without having a negative impact on the color characteristics of food products. Hornung et al. [21] found a light purple coloration for mixtures involving starches from D. trifida (70%) with the species Dioscorea sp. (15%) and D. piperifolia (15%).

D. alata L. is commonly known as Chinese yam, purple yam, or greater yam. It is traditionally used in medicine for its anti-inflammatory and immunomodulatory effects [22]. Among the cultivars, there are all types of forms, and the color of the pulp can vary from homogeneous white or yellow to deep purple [20]. In addition, they are rich in starch, ranging from 59.8 to 83.8%, and have low values of lipids (0.2 to 0.3%) and proteins (5.0 to 6.3%) [23].

D. trifida is a sweet-tasting Andean tuber growing in several regions, mainly Central and South America. The characteristic coloration of D. trifida presents a color tone of 6.84° to 10.76° in the first quadrant of the chromaticity diagram, indicating a color tone between violet and red [24]. D. trifida is formed mainly by carbohydrates, with a content greater than 69.0% (dry mass). These carbohydrates are represented by a significant amount of starch [25]. D. trifida flour has low protein (1.6%) and fiber (2.02%) content.

The anthocyanins make D. trifida a potential source of pigments for the food and cosmetic industries. Ochoa et al. [26] reported that the extraction of anthocyanins from purple yam using the ultrasound-assisted process has better performance than using conventional low-pressure solvent and Soxhlet extraction processes, with yields of up to 22.9% and contents of up to 1.44 mg cyanidin 3-galactoside per g.

The study of root drying seeks to add value to these products as raw material (dye), in addition to considering the interest in the stability of bioactive compounds. In this context, to dry purple yam (D. trifida), it is necessary to dry for 40 min at temperatures of 70, 80, or 90 °C to obtain a humidity of less than 5%. However, there is a loss of pigmentation with increasing temperature due to the decomposition of anthocyanins [24].

A technological property directly affecting the use of roots, such as D. trifida, as dyes is their solubility due to the starch content present. Despite its great potential, the water solubility of this natural ingredient is a critical factor in its application. Santos et al. [24] found that solubility increases as the temperature rises from 25 to 80 °C.

The bioactive properties are improved by drying D. trifida via freeze-drying. The antioxidant activity (ABTS), mainly represented by anthocyanins, has a value of 174.5 µmol TE 100 g⁻¹. Total phenolic compounds also contribute and are present in 513.7 mg gallic acid equivalents (GAE) 100 g⁻¹ [24].

3.1.2. Alpinia officinarum Hance

Alpinia officinarum Hance belongs to the Zingiberaceae (ginger) family and is commonly known as lesser galangal. This rhizome contains 16.9% carbohydrates, 15.2% lipids, 18.2% proteins, and 5.6% ash. Regarding bioactive compounds, flavonoids (5.1%), phenolic compounds (2.7%), and tannins (20.2%) stand out [27].

Its rhizomes have a reddish-brown exterior, while the interior varies from brown to orange. Although the color of these vegetables allows for the extraction of coloring compounds, most studies focus on their medicinal properties [28,29].

Koçak and Yılmaz [30] studied the dyeing of woolen fabric (white) as a natural dye source, using the rhizome powder of A. officinarum without any extraction process. The authors used four different metal salts as mordant materials. In conclusion, the authors found that in addition to coloring the woolen fabrics using the rhizome of A. officinarum, the woolen fabrics gained antibacterial properties (against Escherichia coli and Staphylococcus aureus) naturally, without the need for the addition of mordants.

3.1.3. Xanthosoma riedelianum Schott

Xanthosoma riedelianum Schott, known as mangarito, is an Unconventional Food Plant (UFP) native to Brazil. The rhizomes stand out as a good source of starch and have a yellow color due to the presence of carotenoids. Despite its potential as a dye, there are no studies on this raw material to date.

3.2. Flowers

Edible flowers have been used traditionally for their unique taste and colors. They have been more popular because of the increased number of publications, such as edible-flower cookbooks, magazine articles, and television programs, about them. Edible flowers are rich in natural phytochemicals, including secondary metabolites, natural pigments, essential oils, and natural antioxidants, which have health-promoting effects [31].

Flowers are characterized by the production of striking flower colors, and these colors are primarily caused by the accumulation of pigments in cells of the floral organs. The extraordinary variety of colors displayed in flowers (Figure 2), which range from orange-red to bluish-purple (depending on pH, copigment, and metal ion), are attributed to the presence of four main groups of pigments: chlorophylls, carotenoids, flavonoids, and betalains. In addition to these main groups of pigments, there are other compounds that are extremely rare in wild plants (e.g., quinochalcones in the yellow and red flowers of Carthamus tinctorius and xanthones in some species of iris and gentians) [32].

Anthocyanins are water-soluble pigments highly recognized as colorant molecules, responsible for the coloration of many fruits and vegetables and the petals in most flowers. Flowers can contain a variety of phenolic compounds, which are recognized as natural antioxidants, and their presence is strongly related to their color, either directly (e.g., anthocyanins and other flavonoid pigments) or indirectly through co-pigmentation processes [33]. Edible flowers are being studied as possible sources for producing food additives because of their bioactive properties and natural pigments, providing significant coloring potential.

A change in the specific type of pigment or the mixing ratio of various pigments would affect the resulting color. In contrast, changes in the concentration of the compounds would mainly affect the color intensity. Flowers may show simple, monochromatic colors or extremely complex color patterning, as frequently occurs in species of orchids, irises, milkweeds, or crowfoots. Complex color patterns can be produced by precise and orchestrated regulation of pigment biosynthesis in different parts of the petal [32]. The great challenge for industries in replacing synthetic dyes with natural ones occurs due to the lack of studies on prospecting alternative sources and the instability of natural dyes. The extraction of dyes from flowers has gained prominence due to the growing interest in sustainable and natural solutions in several industries, such as food, cosmetics, textiles, and pharmaceuticals. Flowers are a rich and renewable source of natural pigments, offering several advantages over synthetic dyes.

Some flowers have already been studied as sources of natural dyes for applications in the most diverse areas, such as the food industry, packaging, developing dye-sensitized solar cells, pharmaceuticals, etc. [34]. However, it is essential to study new sources for extracting compounds with dye potential that can be used to replace synthetic dyes. Sonchus oleraceus, Bougainvillea glabra, Impatiens balsamina, Clitoria ternatea, Tropaeolum majus, and Cosmos bipinnatus (Figure 3) are examples of flowers that can be explored for this purpose.

3.2.1. Sonchus oleraceus L.

Within the underutilized edible plants, the genus Sonchus includes annual, biennial, and perennial herbaceous species distributed across Europe, Asia, and Africa. These plants have been traditionally consumed in the Mediterranean regions and are rich in antioxidants, including flavonoids, phenolic compounds, and carotenoids. Sonchus oleraceus, a plant of the Asteraceae family, has yellow flowers that can be exploited to extract natural dyes. The primary pigment present in its flowers is related to flavonoids and carotenoids, which are responsible for the yellow hues [35], representing a promising source of natural dyes, aligning sustainability, functionality, and innovation.

Saxena and Kumar [36] performed phytochemical screening, metal-binding capacity, and applications of the plant S. oleraceus floral extract as a corrosion inhibitor. The phytochemical screening of the extract of S. oleraceus was performed using methanolic extract from the flowers. Phenolic compounds, flavonoids, and tannins were detected.

Studies on the bioactive composition and coloring power of S. oleraceus flowers are scarce in the literature. Most research has focused on the characterization of the leaves or seeds, leaving a gap in the study of flowers as raw material for dye production. Exploring this area could yield valuable new findings to the field.

3.2.2. Bougainvillea glabra Choisy

According to Kumar et al. [37], Bougainvillea is a genus of plants in the Nyctaginaceae family that stand out for their bright flowers, with colors ranging green, magenta, or purple. Bougainvillea glabra, commonly called paper flower, has betalains as its main pigments, particularly betacyanins. Betacyanins are red-violet pigments soluble in water, containing nitrogen in their structure. These pigments are not affected by pH levels and are more stable than anthocyanins, which can be used as food coloring, sensitized solar cells, and medicine.

Natural dye sensitizers from B. glabra (betalain) flowers were prepared using five different ethanol-to-water ratios (0.30, 50, 70, and 90% ethanol), and the effect of dye aggregation on dye-sensitized solar cell (DSSC) performance was evaluated. No definite trend was observed in the Bougainvillea dye extracts as the ethanol concentration increased [38]. Sakalani et al. [39] also extracted dyes from B. glabra as sensitizers for crude and purified dyes in DSSCs and concluded that the photoelectrochemical performance of these extracts demonstrated that crude dyes are more effective than purified dyes as sensitizers in DSSCs applications.

Kumar et al. [37] optimized the extraction process of water-soluble red-purple pigment from the floral bracts of B. glabra using the response surface methodology. The optimal conditions for three process variables were evaluated—the mass of floral bracts (g), temperature (°C), and extraction time (h), each at five levels. The optimal extraction conditions were achieved with 3 g of flowers, an extraction time of 6 h at 22.5 °C, and a maximum absorbance of 9.18.

Rasool et al. [40] studied Bougainvillea flowers (collected from Burewala, Pakistan) as a sustainable and environmentally friendly source of natural plant-based dye, offering an alternative to toxic synthetic dyes for dyeing cotton and silk. The natural dye (anthocyanin) was extracted from Bougainvillea flowers using aqueous and acidic extraction media. The authors claim that the natural dye has potential for use as pigments in the biocoloration of natural fabrics. They also suggest the addition of biomordants enhances the process, making it more environmentally friendly and appealing.

3.2.3. Clitoria ternatea L.

Clitoria ternatea L. (CT), commonly known as butterfly pea, Asian pigeon wings, or bluebell creeper, is a medicinal plant native to Asia but well adapted to several countries. Belonging to the Fabaceae family, its flowers range in color from dark blue to white. These flowers are rich in phenolic compounds, such as cis-resveratrol, naringenin, myricetin, catechin, kaempferol, quercetin, petunidin, and malvidin, and they serve as a source of polyacylated anthocyanins. The greater stability of polyacylated anthocyanins compared to non-acylated anthocyanins makes them advantageous for use as natural coloring agents in foods [41]. Like all anthocyanins, their color varies according to the pH. At a pH less than 3.2, the color is red; at pH 3.2 to 5.2, the color turns blue; at pH 5.2 to pH 8.2, the color is light blue; and at pH 8.2, the color changes to dark green. According to Vidana et al. [34], the anthocyanins from C. ternatea flowers could be used as a blue coloring agent in acidic and neutral food systems. Furthermore, the limited availability of blue food dyes makes anthocyanins from blue pea flowers a promising natural alternative for blue food coloring.

Blue dye can be obtained from synthetic sources such as indigo carmine, patent blue V, and brilliant blue. A new and promising natural source is C. ternatea flowers, which are easy to cultivate and thrive in tropical regions such as Indonesia without requiring advanced technology or high costs. The success of extracting this dye depends on the technique and parameters used. Handayani et al. [42] studied five different solvents and concentrations to evaluate the effectiveness of the extraction process for anthocyanins present in C. ternatea flowers from Indonesia. The authors observed that using 96% ethanol/1.5 N HCl (85:15, v/v) demonstrated superior efficiency, yielding high dye concentrations (200 mg/L). Ultrasound-assisted extraction with glycerol–water (60:40 w/v) was highlighted by Shu et al. [43], where the best results were obtained in 30 min of extraction at 50 °C and a solvent to solid ratio of 10:1. Gonçalvez et al. [44] studied a green method using acidified water at 1% as a solvent for extracting anthocyanins from C. ternatea flowers grown in southern Brazil, also obtaining promising results. Moreover, the efficacy of different conventional solid–liquid extraction methods was evaluated (T1-Aqueous extraction, T2-Acidified aqueous extraction, T3-Solvent extraction, T4-Acidified solvent extraction, and T5-MAE with aqueous solvent and microwave irradiation). Among the extraction methods evaluated, the aqueous method provided significantly higher total monomeric anthocyanin content (7925.29 ± 36.07 mg/L), polymeric color percentage (25.28 ± 1.14%), and higher recovery (73.17 ± 1.76%) [45].

Padmanabhan and Parvatam [46] evaluated the influence of different dehydration procedures—room/shade drying (RD), sun drying (SD), hot air drying (HAD), microwave drying (MD), and freeze-drying (FD)—on the pigments of C. ternatea (CT) petals collected from Mysuru, India. The pigment from the fresh and dried petals was extracted via maceration using three solvent systems: 80% methanol (v/v), 80% ethanol (v/v), and distilled water (aqueous). The blue pigment delphinidin 3-glucoside (D3G) and delphinidin chloride (DC) were found in maximum concentrations in MD petals (95.49 ± 7.80 mg/100 g and 432.02 ± mg/100 g, respectively). Rutin and sinapic acid were the major bioactive compounds detected via UHPLC, with the highest content retained in HAD petals (188.0 ± 1.24 mg/100 g and 2.307 ± 0.82 mg/100 g, respectively). Studies are being conducted to explore the application of these dyes in various industry segments. Cao et al. [40] successfully developed films using CT anthocyanin as indicators of beef freshness. An antibacterial–antioxidant colorimetric film was created by incorporating nisin and pomegranate/C. ternatea anthocyanins (PGA/CTA) into an ethylene vinyl alcohol (EVOH) matrix for monitoring and preserving shrimp freshness. Similarly, Kim et al. [47] developed smart and functional films based on gelatin/agar and CT anthocyanin to monitor shrimp freshness. Gamage et al. [48] investigated the application of these dyes in fermented dairy products, including yogurt and fermented milk, at concentrations of 1 and 2% (w/v). The total anthocyanin content (TAC) in yogurt demonstrated high stability, whereas the TAC in fermented milk decreased significantly. The authors indicate the potential applications of CT-dried blue petals as natural dyes in the food industry.

3.2.4. Tropaeolum majus L.

Tropaeolum majus (nasturtium flowers), belonging to the Tropaeolaceae family, is cultivated worldwide due to its ability to adapt easily to various climates. Its flowers, which range in color from yellow to orange, or red, have a spicy flavor reminiscent of watercress and are used in many countries. Lutein and pelargonidin are the primary bioactive compounds found in nasturtium flowers. While commercial lutein extracts are currently sourced from Tagetes sp. flowers, T. majus presents an excellent alternative for the extraction of this carotenoid. Singh et al. [49] investigated the application of two natural dyes extracted from orange and yellow T. majus flower petals as novel natural sensitizers in DSSC. The dried flowers (vacuum-dried at 60 °C) were ground into a fine powder using a mortar and pestle, and 1 g of each powder was separately dispersed in 50 mL of pure ethanol and left for 24 h. The functional groups present in the dyes were identified by FTIR spectroscopy, which revealed characteristic peaks of pigments such as anthocyanins (cyanidin 3-sophoroside, delphinidin 3-dihexoside, and pelargonidin 3-sophoroside) and carotenoids (primarily lutein), with a higher anthocyanin content in the orange flower extract. Barros et al. [50] analyzed the presence of bioactive compounds in exotic flowers found in São Paulo, Brazil, including T. majus in red and orange varieties. β-carotene was detected at concentrations of 8554.60 μg/g in red capuzin flowers and 7643.21 μg/g in orange capuzin flowers.

Demasi et al. [51] evaluated bioactive compounds in 17 edible flowers found in Northwestern Italy, including T. majus. They reported phenolic compound levels of 341.33 mg GAE/100 g FW and anthocyanin levels of 800.2 mg C3G/100 g FW.

3.2.5. Impatiens balsamina L.

Impatiens balsamina (garden balsam) is an annual herb of the Balsaminaceae family, widely cultivated in Asia as an ornamental plant [52]. Pires et al. [53] investigated the coloring potential of the hydroethanolic extracts from pink (BP) and orange (BO) petals of I. balsamina L. (collected in Paraná, Brazil) by characterizing and quantifying their phenolic compounds (both anthocyanin and non-anthocyanin), studying their bioactivities, and analyzing the chemical and nutritional properties of the petals. Following characterization, the extract with the highest colorimetric and bioactive potential was applied to a pastry product to evaluate its effectiveness as an alternative coloring agent. The results were compared to a control product (without coloring additive) and a formulation containing strawberry gelatin (with coloring additive E163). The findings revealed that both varieties presented significant amounts of phenolic compounds, with 9 non-anthocyanin compounds and 14 anthocyanin compounds identified.

The incorporation of the natural ingredient did not cause changes in the chemical or nutritional composition of the product. Although the color produced was lighter than that of the formulation containing E163 (suggesting a more natural appearance), the higher antioxidant activity could meet the expectations of the current high-demand consumers. The authors suggest that balsam petals could serve as a promising alternative to synthetic dyes.

3.2.6. Cosmos bipinnatus Cav.

Cosmos bipinnatus, commonly known as sunflower, is a plant species belonging to the Asteraceae family. It is an annual flowering plant with inflorescences that feature vibrant petals in colors ranging from violet to pink or lilac, and it has a spicy flavor. Cosmos flowers are characterized by their diversity and high content of phenolic compounds, including rutin, kaempferol, and anthocyanins, with cyanidin 3-glucoside being particularly noteworthy [54]. Information on the potential of cosmos flowers as raw materials for dye extraction is limited. While some studies have evaluated their bioactive composition, no research has been conducted on applying these bioactives for coloring purposes.

Fernandes et al. [55] studied the bioactive compounds and sensory attributes of five edible flowers, including C. bipinnatus. Among the flowers analyzed, the highest levels of monomeric anthocyanins were observed in cosmos (4.18 mg cyanidin 3-glucoside/g DW). The authors observed the relationship between higher anthocyanin concentrations and greater color intensity, more bitterness with higher flavonoid content, and increased astringency with higher tannin levels in cosmos flowers. Ninama et al. [48] evaluated the phytochemical composition of cosmos grown in India. The total carotenoid content reported by the authors was 18.82 µg/g fw, including 0.45 mg/100 g fw of β-carotene and 0.55 µg/g fw of lycopene. Additionally, the total flavonoid content was found to be higher (127.42 ± 0.04 mg/g fw) when water was used as the extraction solvent.

Ortega-Medrano et al. [56] conducted an analysis that revealed the presence of terpenoids, phenolic compounds, tannins, and flavonoids, while alkaloids, saponins, glycosides, and anthraquinones were absent. The extracts demonstrated high levels of phenolic compounds, flavonoids, and condensed tannins. In recent decades, numerous publications have reported advancements in understanding plant-based dyes. However, the benefits and potential applications of flower dyes, as highlighted in this study, remain limited and underexplored. Consequently, these dyes have garnered increased attention in present-day lifestyles. Despite the abundance of edible flowers, detailed scientific data on their natural composition and suitability for use as food ingredients are available for only a few species. There is a pressing need to consolidate scientific information to increase their acceptability, minimize potential risks, and determine appropriate applications [57].

3.3. Leaves

The color of leaves is determined by pigments that play important roles in photosynthesis and protection against solar radiation. The main pigments are chlorophyll, carotenoids and anthocyanins. Some leaves, due to their colorations, can be explored as new sources for the extraction of compounds with coloring potential, such as Basella rubra L., Hibiscus sabdariffa L., and Celosia argentea L. (Figure 4).

3.3.1. Basella rubra L.

Basella rubra L. (Basellaceae), commonly known as Indian or Malabar spinach, is native to tropical and sub-tropical regions. It is a semi-succulent plant, a climbing annual or biennial herb, with circular to ovate leaves that are consumed along with its tender stems. B. rubra has an excellent profile of micronutrients, including vitamins, amino acids, and minerals. Additionally, its leaves and flowers have been found to contain high levels of betalain pigment, mainly betacyanin [58,59,60]. While the twining stems of B. rubra are widely recognized as a leafy vegetable, its fruits, which are rich in betalain pigments, remain largely underutilized [60]. Betalains are water-soluble, nitrogenous pigments derived from tyrosine and found in plants. They are classified into two main groups: yellow orange betaxanthins and red violet betacyanins. Betacyanins, can be further categorized into four types based on their chemical structure: betanin, amaranthin, gomphrenin, and bougainvillein [61]. The content of each compound can vary depending on the extraction process and the plant’s physiological characteristics.

Kozioł et al. [59] evaluated the betacyanin content in the leaves and flowers of B. alba grown in a greenhouse. The total content of gomphrenins in B. alba “Rubra” leaves was measured at 11.2 mg/100 g. Although this concentration is lower than that found in the fruits, B. alba leaves remain an attractive source of betacyanins. Kumar, Manoj, and Giridhar [61] demonstrated that the betalain pigment content in B. rubra leaves varies with plant age. The total betalain content in one-week-old leaves was 6.4 mg/100 g, increasing significantly to 80 mg/100 g at 20 weeks. After this point, there was a drastic decrease in pigment content due to leaf senescence. Using this pigment as a food colorant not only enhances the visual appeal of food but also offers potential health benefits. Identifying suitable extraction conditions for recovering bioactive components is essential to maximize their health-improving effects [62]. Usually, the extraction process is simple and uses water as the extraction solvent [60,61,63]. Maran and Priya [64] employed ultrasound-assisted extraction to enhance pigment yield. The optimal extraction conditions were determined to be a temperature of 54 °C, ultrasonic power of 94 W, extraction time of 32 min, and a solid-to-liquid ratio of 1:17 g/mL. Under these conditions, the extraction yielded 1.43 mg/g of betacyanin and 5.37 mg/g of betaxanthin. Although betalain pigments are valued for their natural origin and are used in some food applications, their broader adoption is significantly hindered by their low stability under various physicochemical conditions [58]. This highlights the critical need for studies focusing on pigment stability. However, despite their importance, such studies remain scarce. Betalains exhibited the lowest degradation within a pH range of 4 to 6. When incubated at temperatures of 4 °C, 20 °C, and 60 °C, only a slight decrease in pigment stability was observed over 2 h. Regarding light exposure, the degradation rate of pigments in fruit extracts was slower under dark conditions compared to those exposed to light [63]. Encapsulation techniques have been explored in studies as a strategy to enhance pigment stability.

The study carried out by Sravan Kumar et al. [65] evaluated the encapsulation of betalains extracted from B. rubra juice into liposomes and their application in gummy candies. Encapsulation significantly enhanced the stability and bioactivity of the pigments. The results demonstrated that the DPPH radical scavenging activity of the samples increased proportionally with the concentration of encapsulated betalains. Furthermore, the authors reported a high retention (95%) of total betalains, particularly betacyanins, in gummy candies fortified with the encapsulated pigments. The co-crystallization process, an encapsulation technique, has been shown to enhance the stability of betacyanins extracted from B. rubra fruits [66]. Specifically, co-crystallization with sucrose and sucrose–gum acacia reduced the degradation rate constant by 2.5-fold and 7.7-fold, respectively. The authors suggest that the increased stability of betacyanins with sucrose–gum acacia is likely due to the formation of a gum acacia film on the porous agglomerate structure, which provides enhanced protection to the encapsulated labile compounds, shielding them from oxidation and other degradative processes. Studies on new products developed using B. rubra extracts or pigments derived from this species are still rare. Karangutkar and Ananthanarayan [58] developed a beverage containing sucrose, sodium benzoate, buffer solution, and crude extract of B. rubra (0.4% v/v). The beverage, prepared with different concentrations of additives, was stored under accelerated storage conditions of 40 °C for 0 to 5 days to determine the pigment degradation. According to the authors, the stabilizer catechin, EDTA, and β-cyclodextrin improved betacyanin stability when stored at refrigerated temperatures, in the absence of light and oxygen. On the other hand, ascorbic acid acted as a pro-oxidant at a concentration of 0.05%. Kumar, et al. [61] incorporated B. rubra juice derived from fruits into an ice cream formulation consisting of milk powder, sugar, and butter. The resulting ice cream showed high acceptance, with 60% of the panelists rating it as “liked very much”. Additionally, there was no significant decrease in color after 180 days of storage at −20 °C, with a color retention of 86.6%.

Sravan Kumar et al. [60] developed B. rubra fruit juice containing red-violet betalain pigment, which was fermented to decrease the total soluble solids, with the aim of achieving a higher pigment concentration. The behavior varied depending on the Saccharomyces cerevisiae used. During the 3–6 h fermentation process, the changes in total pigment content were in line with changes in betacyanin and betaxanthin content, with an increase in betacyanins levels observed from 3 to 6 h of fermentation. The changes in pigment content of B. rubra juice were consistent with variations in L*, a*, and b* values during fermentation by yeast.

These studies have identified B. rubra as a valuable source of betalain pigments, which not only offer health-promoting properties but also enhance the color of foods as natural coloring agents. However, further research is necessary to explore its full potential.

3.3.2. Hibiscus sabdariffa L.

Hibiscus sabdariffa L. (roselle), a member of the Malvaceae family, is an annual herbaceous shrub widely cultivated in tropical and subtropical regions. The species is usually cultivated for its fibers and calyces and includes three different genotypes: green, red, and dark red. The plant’s leaves are commonly utilized as animal fodder, leafy green vegetables, and for fiber production, while the calyces constitute the primary component of commercial interest [67,68,69].

The composition of H. sabdariffa is rich in phenolic compounds, organic acids, and polysaccharides. The flowers of H. sabdariffa contain a high concentration of anthocyanins, with key phytochemicals including proanthocyanins, flavan-3-ols, tannins, catechins, and cyanogenic glycosides. Their primary industrial use as dyes is attributed to their diverse and vibrant color range, spanning from red to purple [67,68,69].

In addition, due to its bioactive compounds and antioxidant, antimicrobial, and medicinal activities, the pigment potential of H. sabdariffa extract has been extensively studied. Jabeur et al. [67] found that the lyophilized hydroethanolic and infusion extracts of H. sabdariffa exhibited antibacterial and antifungal activities. According to the authors, these effects can be attributed to the richness in phytochemical metabolites, such as phenolic acids (e.g., protocatechuic acid) and anthocyanins (e.g., delphinidin 3-O-sambubioside and cyanidin 3-O-sambubioside).

The key to pigment use lies in the extraction process. Li et al. [70] evaluated the effect of solvents and water to pigment extraction. They observed that when 100% water was used as the extraction solvent, the calyx/solvent slurry became very thick and viscous, making it difficult to separate the extract from the hydrated calyces via reduced-pressure filtration. As the ethanol content increased, the calyx/solvent slurry became less viscous, allowing for easier and faster separation. The optimal extraction conditions were found to be at 50–70% alcohol content in the solvent, with double extractions, which improved recovery and reduced process costs. According to Villalobos-Vega et al. [71], organic acids, phenolic acids, flavonoids, and anthocyanins presented in H. Sabdariffa are soluble in hydroalcoholic mixtures containing equal amounts of ethanol and water, but their solubility decreases when ethanol concentration nears the azeotrope. Nwuzor et al. [69] evaluated the effect of temperature, time, and amount of feed material during the extraction process with ethanol as solvent. According to the study, the size of the roselle flower was the major factor that affected the yield due to the contact surface with the solvent. The highest extract yield (68%) was obtained at a 100 °C temperature, 60 min time, and 1 kg feed material.

Emerging technologies have been applied to enhance extraction yields to identify more efficient and environmentally friendly methods. Pinela et al. [72] studied two processes—heat-assisted and ultrasound-assisted extraction—to obtain anthocyanins from H. sabdariffa calyces. The content of anthocyanins obtained through ultrasound-assisted extraction was nearly three times higher than that obtained by heat-assisted extraction. These results suggest that H. sabdariffa calyces can be considered a viable source of anthocyanins to produce bio-based coloring agents. However, further studies are needed to scale up the process and explore its potential applications for industrial suppliers in sectors such as food, pharmaceuticals, and cosmetics.

Ngoc Nhon et al. [73] investigated microwave-assisted extraction, ultrasonic-assisted extraction, enzyme-assisted extraction, and their combinations to enhance anthocyanin content from H. sabdariffa. Both ultrasound and microwave methods improve extraction efficiency by increasing temperature and pressure within cells, disrupting their structure, and facilitating solvent penetration. This accelerates cell wall hydrolysis during enzyme treatment, further enhancing extraction. These methods are efficient, easy to apply, and require short extraction times. However, microwave irradiation, following enzyme-induced cell degradation, increases the contact area between solid and liquid phases, allowing for better solvent access to valuable components. The combination of ultrasound at the end of extraction did not further improve anthocyanin recovery. As a result, microwave-enzyme-assisted extraction was selected for its superior efficiency. The use of supercritical carbon dioxide (SC-CO₂) has proven to improve the yield and stability of anthocyanins, as demonstrated by Idham et al. [74]. Recent studies have also explored alternative green extraction methods, such as the use of natural deep eutectic solvents (NADESs). According to these studies, NADESs, particularly those composed of organic acids like lactic and oxalic acid, exhibit higher extraction yields of anthocyanins, suggesting that their acidic nature enhances the extraction capacity of these valuable compounds. Together, these methods highlight promising alternatives for the efficient and sustainable extraction of anthocyanins from H. sabdariffa [75].

The main challenge in using anthocyanins lies in the stability of their pigments under varying conditions such as pH, temperature, light exposure, and oxygen levels. Therefore, studies on pigment stability are essential to understanding their feasibility in industrial applications, ensuring the preservation of their properties throughout processing and storage [76,77]. The chemical structure of anthocyanins is closely related to the stability, and the presence of an acyl group has demonstrated a positive effect on color stability, as presented by [68,77].

Pereira et al. [77] evaluated color stability under different conditions, including variations in pH (2–7), temperature (60 and 100 °C), and the process of sodium bisulfite bleaching. H. sabdariffa was purchased from a local supermarket, and their pigments were extracted from flowers by adding boiled water. The hibiscus calyxes extract exhibited an acidic pH (3–4) and, at pH 2, showed the a* coordinate related to the red color. However, at pH 4–5, the color changed to light pink (due to the presence of the non-colored hemiketal form) and then adopted brownish hues (due to the presence of quinoidal and chalcone forms) near a neutral pH. This behavior was also observed by Teixeira et al. [78]. After seven days, the samples showed lower stability, resulting in absorbance decreases of 2% at pH 2, 33% at pH 3, and 70–80% after 4 days at a neutral pH. The rate of color degradation at 100 °C was 5.5 × 10⁻³ min⁻¹, and after 2 h of the experiment, there was a 50% loss of the initial anthocyanin concentration. According to the authors, the hibiscus calyxes extract is mainly composed of non-acylated anthocyanins, and thermal degradation is related to the hydrated form of anthocyanins [77]. One effective strategy to improve color stability is encapsulation. This process protects the active compounds from environmental factors, thereby enhancing their stability and extending the product’s shelf life. Millinia et al. [76] investigated the microencapsulation of roselle calyx extract via spray drying with maltodextrin and a maltodextrin-trehalose blend to enhance pigment stability. Encapsulation yields ranged from 44.4% to 73.6%, with the 50:50 maltodextrin-to-extract ratio producing powders with optimal physicochemical properties and improved antioxidant activity. Ngoc Nhon et al. [73] evaluated the encapsulation of pigments using maltodextrin and gum arabic as encapsulating agents to enhance color stability and antioxidant activity. The shelf life achieved was up to 468 days, and antioxidant activity remained above 50% during 20 days of accelerated shelf-life period. These results are related to the wall materials used. The anthocyanins and flavonols present in H. sabdariffa can form complexes with polysaccharides, so the combination of gum arabic with maltodextrin may provide higher effectiveness [79]. However, the selection of wall material plays a crucial role in determining the stability and performance of the encapsulated pigment. Nguyen et al. [80] evaluated the encapsulation of Hibiscus anthocyanins in yeast cells and concluded that the endogens enzymes of yeast caused undesirable color loss during storage. This issue was mitigated by inactivating the enzymes through heat treatment (75 °C for 5 min). After pretreatment, the color loss was only 2.5% for heat-treated yeast, compared to 36.5% for untreated yeast at 37 °C. The evaluation of pigment stability is crucial from a technological perspective, as it provides essential insights into the types of products where the pigment can be effectively utilized. The primary application of roselle calyces is in beverages [71,81,82].

Halim et al. [83] evaluated different concentrations of dried roselle calyces as a natural colorant in jelly candy to replace synthetic colorants. A sensory evaluation questionnaire, involving 16 formulations of jelly candy containing varying levels of dried roselle calyces and sucrose, was administered to 70 untrained panelists. The formulation with 63.6% sucrose and 16.7% dried roselle calyces achieved the highest scores in overall acceptance, color, and sweetness, with a rating of 4.97. This formulation is recommended as a healthier alternative for sweet treats.

Teixeira et al. [78] used H. sabdariffa extract obtained from flowers in yogurt as a natural dye to replace artificial food dyes. Hibiscus flowers were added to distilled water at 85 °C, and the mixture was blended at 7000 rpm for 20 min. The mixture was then subjected to vacuum filtration and lyophilized to obtain the Hibiscus extract. The dried extract (0.1 g) was mixed with 10 mL of yogurt. The authors noted that due to the anthocyanins’ strong resistance to acidic pH, the yogurt retained its color, showcasing the characteristic hue of the hibiscus extract. In contrast, another study found that milk flavored and colored with roselle extract was generally accepted by consumers in terms of taste, but the color was considered unappealing. These results were attributed to pH fluctuations and color instability, as indicated by the authors [84]. Radhouane et al. [82] used an aqueous extract from hibiscus flowers to produce an isotonic drink. The drink formulation consisted of thermal water (33%), apple juice (45%), and hibiscus extract (22%, at 40% concentration). This recipe provided the best combination of taste and color. The hibiscus extract supplied antioxidant compounds and added an appealing color to the product due to its anthocyanin content. The best storage conditions for color and anthocyanins preservation were at 4 °C.

Hoang et al. [79] applied anthocyanin power obtained from H. sabdariffa in different levels (1–7%) in a marshmallow formulation, with a control group using carmine, a synthetic colorant. The acceptance of the developed marshmallows was then evaluated. According to the hedonic scale, the control sample and MC-5% (marshmallow containing 5% anthocyanin powder) were the most accepted. The key factors influencing the acceptability of the MC-5% candy were its color appearance and aroma homogeneity. In contrast, the MC-1% and MC-3% samples appeared slightly pale, while the MC-7% sample had a deep pinkish color and a carrot-like flavor, which was less preferred by the testers. Regarding purchase intent, 78% of consumers expressed a positive attitude toward buying the MC-5%, while 75% showed interest in the control sample, indicating they would likely purchase it, according to the scale used. In addition to their applications in food and beverages, anthocyanidins extracted from H. sabdariffa are also used in other industries, such as the textile and cosmetic sectors [85]. Mansour and Ben Ali [86] investigated the effect of chitosan on the dyeing properties of cotton fabrics dyed with roselle (H. sabdariffa L.). Their study demonstrated that pretreatment with chitosan alters the pH of cotton and enhances the dyeing process, resulting in greater color strength compared to untreated cotton.

Recently, roselle calyx extract has been used as a natural colorant in polymers [87,88]. The primary aim of these studies was to replace hazardous synthetic pigments in the plastic polymer industry. According to the authors, the roselle calyx extract enhanced film crystallinity and improved compatibility with polybutylene succinate, with no significant differences observed in the physical or mechanical properties of the developed films. Furthermore, films incorporated with 0.1 wt% of the extract exhibited improved light barrier properties, reducing UV-A transmission by 88% and visible light transmission by 91.3%.

3.3.3. Celosia argentea L.

Celosia argentea L. (cock’s comb), a member of the Amaranthaceae family, is an herbaceous plant cultivated for its adaptability and the aesthetic appeal of its vibrant inflorescences. Beyond its use in landscaping, the plant plays a significant role in traditional medicine, where it is employed across various cultures to treat inflammations and other health conditions [89,90]. Its historical and functional relevance, combined with bioactive pigments such as betalains, justifies the growing interest in studying this plant for natural compound research [91]. Betalains have been studied for their potential as natural colorants in food, cosmetics, and other industries. Recent studies highlight their promise as sustainable alternatives to synthetic dyes, given their broad availability and ease of cultivation [90,91]. C. argentea includes several varieties, such as C. argentea var. cristata and C. argentea var. plumosa, which differ in traits like the shape and coloration of their inflorescences. These variations are important as they directly influence the pigment content and quality. For instance, more vibrant inflorescences are associated with higher betalain concentrations, resulting in more intense extracted colors and expanding their application as natural colorants [89,91]. Betalains extracted from C. argentea have attracted attention for their antioxidant properties in addition to their role as natural pigments. Studies have shown that methods like ultrasound-assisted extraction and the use of binary solvents are effective in increasing yield and compound stability [91,92]. In particular, extracts obtained with ethanol concentrations between 40% and 60% demonstrated higher betacyanin content and superior antioxidant activity, comparable to synthetic antioxidants such as ascorbic acid [92].

Beyond its application as a food colorant, C. argentea has also been evaluated for other industrial functions. A recent study developed temperature sensors based on betalains extracted from C. argentea var. cristata, highlighting their sensitivity to thermal variations in food packaging. These sensors visually indicate changes in product quality through color shifts, offering an innovative application of natural pigments beyond conventional uses in food and cosmetics [93].

Studies with other betalain-rich plants, such as Beta vulgaris and Amaranthus hypochondriacus, provide valuable insights for optimizing the extraction and stability of these pigments in C. argentea. For example, research using deep eutectic solvents for betalain extraction from beetroot has shown promising results regarding bioaccessibility and stability, which could be adapted for C. argentea [94]. Similarly, microwave-assisted extraction in amaranth leaves revealed an efficient method for recovering betalains from agro-industrial residues, suggesting a sustainable approach applicable to other species [95].

These studies support the findings for C. argentea, reinforcing its potential as a sustainable source of natural colorants. However, challenges remain, including the standardization of extraction methods and the analysis of pigment stability under different industrial conditions [85,86]. Future studies should focus on exploring the plant’s varieties further, optimizing both cultivation and the commercial application of its pigments [96].

3.4. Fruits

Fruits have already been studied to obtain dyes, which can be extracted from the peels or pulp, but studying new fruits that can offer this coloring capacity to be applied in various industrial areas is extremely important, and, with this, unconventional fruits have been gaining prominence; we can mention new studies on Rubus rosifolius Smith, Syzygium jambos (L.) Alston, Solanum betaceum Cav., Clidemia hirta (L.) D. Don, Genipa americana L., and Eugenia brasiliensis Lam. (Figure 5).

3.4.1. Rubus rosifolius Smith

The wild blackberry (Rubus rosifolius Smith), a member of the Rosaceae family, is a small, dark-colored fruit widely distributed across temperate and subtropical regions. Known for its rich nutritional profile and bioactive compounds, blackberries have gained popularity in recent years due to their versatility and health benefits.

These fruits present interesting phenolic compounds, such as catechins, ellagic acid, and quercetin derivatives, which contribute to their bioactivity and antioxidant capacity. Anthocyanins, water-soluble flavonoids from the phenolic compound family, offer antioxidant properties that enhance the health benefits and environmental resilience of plants. In fact, blackberries have proved to adapt to abiotic stresses like UV radiation and metal toxicity by increasing anthocyanin production [97,98]. Anthocyanins are also responsible for the red, purple, and blue hues in the fruit, making them a natural pigment with potential applications across multiple industries, including food, cosmetics, and textiles [99]. Total anthocyanin content in blackberries has been documented to range from 250 to 270 mg per 100 g of dry weight. The main anthocyanins detected include cyanidin 3-rutinoside, cyanidin 3-sophoroside, cyanidin 3-xylosyl-rutinoside, pelargonidin 3-glucoside, and cyanidin 3-O-glucoside, with the latter being the most abundant compound [100]. The extraction of anthocyanins from blackberries has been optimized using both conventional and innovative methods. Among the conventional methods, hydroalcoholic solutions are commonly used. For instance, Moraes et al. [101] employed a mixture of methanol–water with 0.1% hydrochloric acid as the solvent, performing the extraction for one hour at room temperature with continuous agitation. Although effective, this approach requires multiple filtration and drying steps to maximize the yield of the extracted compounds.

Among non-conventional methods, ultrasound-assisted extraction (UAE) has proven to be particularly efficient. Zafra-Rojas et al. [97] optimized this method using a power of 325 W and an extraction time of 7.5 min, which resulted in high yields of anthocyanins and significant preservation of antioxidant activity. UAE works through acoustic cavitation, which breaks down cell walls and improves the solubility of bioactive compounds in the solvent. This method is highly regarded for its efficiency and lower solvent requirements compared to conventional extraction techniques. Pressurized liquid extraction (PLE) is another advanced method used for anthocyanin extraction from blackberries. In a study by Machado et al. [102], PLE was performed with an ethanol-water mixture (60:40 v/v) under a pressure of 1000 psi and a temperature of 80 °C for 10 min. This method was found to extract anthocyanins more efficiently than conventional techniques, particularly from blackberry residues, yielding a high concentration of cyanidin-based anthocyanins. The application of pressure and temperature in PLE enhances the solvent’s ability to penetrate plant tissues, facilitating the extraction of bioactive compounds in shorter extraction times. Compared to other emerging methods, UAE stands out for its energy efficiency and reduced chemical solvent usage. Furthermore, adjusting variables such as time and power allows for method adaptation to different blackberry matrices and industrial requirements. The combination of UAE with techniques like freeze-drying has also shown promise in preserving anthocyanin stability and antioxidant properties, making it highly suitable for food and cosmetic applications.

In this context, wild blackberries emerge as a natural and compelling source of anthocyanins, with applications as natural pigments that can replace chemical dyes, offering significant benefits for consumers. In the food industry, anthocyanins from blackberries serve as natural colorants in beverages, jams, yogurts, and confectionery [102,103], enhancing both the aesthetic and nutritional profiles of these products. Mohammadi et al. [99] explored the use of freeze-dried blackberry extracts in the production of functional gummies. These gummies were fortified with blackberry extracts, which not only provided natural color but also contributed antioxidant and anti-inflammatory properties. The study demonstrated that the gummies enriched with blackberry extracts showed higher phenolic and anthocyanin content compared to commercial counterparts. Additionally, sensory evaluations indicated that these functional gummies were well accepted by consumers in terms of taste and texture. In another study, blackberry extracts were used to color yogurts. The freeze-dried blackberry powders were incorporated as natural colorants, and the final products exhibited good color stability and high antioxidant activity. This study highlighted the potential of blackberry extracts as a sustainable alternative to synthetic colorants in dairy products, aligning with the growing consumer demand for natural and functional ingredients.

In the textile industry, blackberry extracts are explored as natural dyes. A study by Repon et al. [104] examined the application of bio-mordants and natural dyes derived from plant extracts, including blackberry, to improve textile properties. The study highlighted that when these natural dyes are used in conjunction with bio-mordants, they can improve colorfastness and offer additional benefits, such as UV protection. Bio-mordants, which enhance the bonding of the dye to the fabric, were shown to reduce the need for synthetic chemicals, making the process more sustainable and environmentally friendly. However, the challenge remains to optimize the durability and consistency of natural dyes like blackberry, as they can be affected by seasonal and geographical variations.

3.4.2. Syzygium jambos (L.) Alston

Syzygium jambos (L.) Alston, commonly known as the rose apple, belongs to the Myrtaceae family and is renowned for its versatile applications in traditional medicine and modern science. Native to Southeast Asia, it has also been naturalized in tropical regions such as India and the Caribbean. The tree grows to a height of 7.5 to 12 m and bears fruits with a pale yellow to pinkish hue [105]. The fruit’s thin, smooth epicarp and succulent mesocarp make it visually appealing and a source of natural pigments [106]. The fruits and other parts of S. jambos are rich in bioactive compounds. Key classes include flavonoids (e.g., quercetin, myricetin, and kaempferol), ellagitannins, and phenolic acids. These compounds contribute to the plant’s antioxidant, antimicrobial, and anti-inflammatory properties. Flavonoids, particularly anthocyanins, are among the most prominent bioactive compounds found in S. jambos. These pigments contribute significantly to the fruit’s vivid red and purple hues and possess strong antioxidant properties. Anthocyanins identified in the fruit include cyanidin 3-glucoside, delphinidin 3-glucoside, and pelargonidin derivatives. The total anthocyanin content in S. jambos has been reported to range between 50 and 120 mg per 100 g of fresh weight, depending on factors such as ripeness, environmental conditions, and extraction methods [105]. Studies such as those by Gavillán-Suárez et al. [106] have demonstrated a high correlation between anthocyanin concentration and antioxidant activity, emphasizing their potential as natural colorants and functional food ingredients. These polysaccharides, apart from their medicinal value, exhibited vivid coloration that could be exploited in nutraceuticals.

Several advanced techniques have been employed to optimize the extraction of anthocyanins from S. jambos, leveraging both traditional and modern methodologies to achieve high yields and preserve compound integrity. Gavillán-Suárez et al. [106] utilized a hydroalcoholic solvent system with acidified ethanol for solid–liquid extraction, demonstrating that adjusting parameters such as pH, temperature, and duration significantly enhanced anthocyanin recovery.

The use of S. jambos as a natural dye spans multiple industries, including food, textiles, and pharmaceuticals. The pigments extracted from S. jambos fruits have been incorporated into confectioneries and beverages as a colorant. Tamiello et al. [107] highlighted the excellent lightfastness and wash durability of textiles dyed with S. jambos, suggesting its use as an eco-friendly alternative to synthetic dyes. Additionally, anthocyanins from the fruit have been used in experimental drug delivery systems, leveraging their natural color to monitor dispersion while benefiting from their bioactivity.

Syzygium jambos offers an exciting opportunity for the development of natural colorants, supported by its rich phytochemical profile and versatile applications. With further optimization of extraction techniques and standardization, it holds the potential to replace synthetic dyes in various industries, aligning with global sustainability goals.

3.4.3. Solanum betaceum Cav.

Solanum betaceum Cav., commonly known as tamarillo or tree tomato, is a versatile plant belonging to the Solanaceae family. Native to the Andean highlands of South America, this perennial species thrives at altitudes between 1500 and 3000 m, in tropical and subtropical climates with moderate rainfall and well-drained soils. Its fruit, characterized by its vivid red, orange, or purple hues, is an abundant source of bioactive compounds, particularly anthocyanins and carotenoids. These pigments hold significant potential as natural colorants in food, textile, and pharmaceutical applications, driven by growing consumer demand for sustainable alternatives to synthetic dyes.

The vibrant coloration of S. betaceum fruits is primarily due to anthocyanins, notably cyanidin 3-O-rutinoside, cyanidin 3,5-O-diglucoside, and delphinidin derivatives, which impart red to purple hues. Additionally, carotenoids such as beta-carotene and lutein are responsible for orange and yellow tones. These compounds are valued for their antioxidant properties and stability in acidic conditions, making them suitable for applications in food matrices [108]. Moreover, glycosylation of anthocyanins enhances their water solubility, a crucial factor for their usability in industrial processes [109]. High-performance liquid chromatography (HPLC) and spectrophotometric analyses have been employed to characterize these pigments, revealing concentrations of up to 100 mg/kg of fresh fruit for anthocyanins and significant carotenoid content in the peel and pulp [110].

The efficiency of pigment extraction from S. betaceum depends on the extraction method and operational parameters used. Solvent-based methods using ethanol or methanol acidified with hydrochloric acid have been widely adopted [111]. Advanced techniques, such as microwave-assisted extraction (MAE) [112] and ultrasound-assisted extraction (UAE) [113], have demonstrated enhanced yields and shorter processing times. In MAE, Silva et al. [114] investigated the extraction of lycopene from processed S. betaceum waste using UAE. Their study identified optimal conditions for the process, including an extraction temperature of 63.4 °C, a solvent mixture containing 30% ethyl acetate (v/v), a solvent-to-solid ratio of 100 mL/g, and an extraction time of 20 min. Under these parameters, the lycopene yield reached 1.33 mg/g of dry waste, demonstrating an important improvement in extraction efficiency compared to similar conditions without the application of ultrasound. De Andrade Lima et al. [115] also optimized a method based on pressurized-liquid extraction, using 0.46 g of S. betaceum at 59 °C, 350 bar, and 15% (v/v) ethanol for 30 min, achieving a 90% recovery of carotenoids. Anthocyanins and carotenoids from S. betaceum are increasingly used as natural food colorants due to their stability under acidic conditions and health-promoting properties. Osorio et al. [116] demonstrated their application in gummy candy production. In this study, tamarillo anthocyanins were incorporated into the candy matrix at concentrations of 0.1–0.5% (w/w), achieving vibrant red hues with high consumer acceptability. The candies were stored at 25 °C for 14 days, maintaining over 90% color intensity without significant degradation. These results highlight the potential of S. betaceum extracts for confectionery applications.

For the energy sector, tamarillo fruit extracts have demonstrated potential as photosensitive dyes for dye-sensitized solar cells (DSSCs), as reported by Susanti et al. [117]. These photosensitive dyes capture photons of light, utilizing their energy to excite electrons. The solar energy industry increasingly values natural dyes for their minimal environmental impact, non-toxic nature, and eco-friendliness compared to synthetic alternatives. Susanti et al. [117] successfully developed a TiO₂-based DSSCs using tamarillo-derived dyes, achieving a maximum efficiency of 0.043%, an open-circuit voltage of 542.5 mV, and a short-circuit current density of 0.356 mA/cm². The pigments present in tamarillo, including anthocyanins, carotenoids, and chlorophylls, acted as effective photosensitizers, facilitating solar energy conversion into electrical energy via a semiconducting photoanode. Further studies are needed to compare the performance of tamarillo-extract-based DSSCs with those sensitized by other fruit extracts. Expanding the non-food applications of tamarillo products will require innovative approaches and diversification.

3.4.4. Clidemia hirta (L.) D. Don

Clidemia hirta (L.) D. Don (soapbush) is a shrub species native to South America, found from Mexico to southern Brazil [118]. It is a pioneer, invasive, and weedy species, characterized by glandular trichomes on the branches, cordate to subcordate leaf bases, and ripe purple fruits with showy white petals. The plant produces small, clustered fruits, bluish-purple in color when ripe, ranging in size from 9 to 10 mm. Each fruit contains between 700 and 1200 small seeds, which are considered edible and have a sweet flavor [119]. The phytochemical composition of C. hirta has been studied, revealing a variety of polyphenolic compounds. Specifically, it has a high total flavonoid content, ranking as the highest among the Melastomataceae species studied [120]. In terms of pigments, C. hirta is known to contain anthocyanins, which are responsible for the blue-purple color of its ripe fruits. The anthocyanin content in C. hirta fruits has been studied, and the fruits have been considered a potential source of natural colorants [119,121]. According to Assunção-Júnior et al. [122], in their study on anthocyanin profiles, C. hirta showed specific phenolic acid profiles, with a total anthocyanin concentration of 1848.38 μg/100 g. The dominant anthocyanins were delphinidin 3-O-rutinoside and cyanidin 3-O-glucoside.

Studies on the extraction of anthocyanins from C. hirta fruits have been conducted. Larasati et al. [119] found that extraction at 60 °C for 30 min yielded the best result, with 43.81 ± 2.99 mg/L of total monomeric anthocyanins and 1.31 ± 0.12 g/L of phenolic compounds as the gallic acid equivalent. They also observed that C. hirta extract exhibits a red color at pH 1 and 3. Alternatives for the more stable use of this pigment have been developed. In a study by Mar et al. [123], C. hirta extract encapsulated in maltodextrin with different dextrose equivalents (DEs) demonstrated excellent antioxidant properties, with DPPH (994 ± 14 μM trolox equivalents (TE)) and ABTS (1273 ± 18 μM TE) values. The encapsulation efficiency was high, ranging from 97.0 to 99.8% (DPPH) and from 87.8 to 99.1% (ABTS). The microparticles obtained through lyophilization, especially with low DE maltodextrin, ensured greater stability and retention of the bioactive compounds, with a half-life of approximately 45 days under 22% relative humidity. Furthermore, the phytochemical composition and biological activities of C. hirta extracts have been studied. Bomfim et al. [120] found that hexane extract of C. hirta showed no antimicrobial activity, while the ethyl acetate and methanol extracts exhibited both antimicrobial and antioxidant properties. These properties make C. hirta a potentially valuable source of natural antioxidants and bioactive compounds for various applications, including cosmetics, the food industry, and traditional medicine.

3.4.5. Genipa americana L.

Genipa americana L., commonly known as jenipapo or jagua fruit, is a tropical tree species native to Central and South America [124]. G. americana is considered an economically and ecologically important species, with its fruits used to produce jellies, jams, liqueurs, and other food products [125]. The tree is also valued for its timber and potential use in agroforestry systems and in the restoration of degraded areas [124].

Morphologically, the fruit of G. americana is an ovoid berry ranging from 5 to 10 cm in size, with a hard, green exocarp that turns purple or black upon ripening. The fruit contains a variety of bioactive compounds, including flavonoids, tannins, and iridoids, such as geniposide and genipin [126], which contribute to the bioactivity of the fruit. Studies have shown that extracts from G. americana fruits exhibit antibacterial, antifungal, and cytotoxic activities, suggesting potential applications in the food, cosmetic, and pharmaceutical industries [127,128].

When the green jenipapo fruit is exposed to air or reacts with amino acids, the geniposide compound present in the fruit, which is naturally colorless, is converted into a blue pigment genipin, which has several potential applications [129]. The mechanism by which genipin (GN) promotes the formation of the blue dye involves interactions with primary amino acid residues, leading to the creation of a blue pigment through a series of chemical reactions. Initially, GN interacts with primary amino groups, such as those found in amino acids or proteins, and a nucleophilic attack occurs. The amino group attacks the carbon atom at the C3 position of the GN molecule, leading to the opening of the GN ring and the production of an aldehyde residue. This process results in the formation of a GN heterocyclic derivative, in which the formation of the blue pigment is attributed to the polymerization of these GN–amine complexes, which involve additional interactions that create larger molecular structures. These GN–amine heterocycles can undergo further reactions, particularly in the presence of oxygen, leading to the polymerization that produces the blue pigment [130]. In this context, the resulting blue dye exhibits stability under various conditions, including thermal and pH variations, making it suitable for use in food and textile applications. The intensity and stability of the color can also be influenced by the specific amino acid involved and the concentration of NG used [131].

The blue pigment derived from the jenipapo fruit, also known as “jagua blue”, has been investigated as a potential natural food colorant to replace synthetic dyes [132]. Studies have shown that the pigment exhibits good stability and color properties, making it a promising alternative as a colorant in various food and textile products. Náthia-Neves et al. [129] investigated the optimized extraction of the natural blue dye genipin, obtained from the jenipapo fruit, using pressurized liquid extraction (PLE), low-pressure extraction (LPSE), and pressing followed by LPSE (Press + LPSE). They studied the effects of solvent (water and ethanol), temperature (40, 50 and 60 °C), and pressure (0.1, 2, 5 and 8 MPa). The results showed that the extraction processing time could be reduced from 22.2 min to 5.84 min.

3.4.6. Eugenia brasiliensis Lam.

Eugenia brasiliensis Lam., commonly known as grumixama or brazilian cherry, is a tree species native to the coastal forests of Brazil. The fruit is approximately 2 cm in diameter, with smooth, shiny skin that ranges in color from red to purple [133,134].

In terms of fruit quality and composition, the grumixama exhibits considerable variation in parameters such as soluble solids, titratable acidity, and volatile organic compounds, depending on the specific accession or variety [134]. Additionally, the leaves, fruits, and bark of the E. brasiliensis tree have been traditionally used in folk medicine for the treatment of various conditions, such as rheumatism and diarrhea, and as a diuretic. The grumixama fruit is known to be a rich source of various bioactive compounds, including vitamins, phenolic compounds, and anthocyanins [135]. These bioactive compounds have been investigated for their potential as dyes with applications in the food, cosmetic, and pharmaceutical industries [135].

One of the compounds of greatest interest in the grumixama fruit is anthocyanins, which contribute to its characteristic red-to-purple coloration. The major anthocyanins identified in the fruit include cyanidin 3-glucoside and delphinidin 3-glucoside [136]. Studies have shown that the anthocyanins from E. brasiliensis exhibit potent antioxidant and anti-inflammatory properties and could be a good natural dye with various applications. Extraction methods such as pressurized liquid extraction and ultrasound-assisted extraction have been explored to optimize the recovery of anthocyanins from E. brasiliensis fruits. The anthocyanin content in the fruit can vary depending on factors such as cultivar, growing conditions, and fruit maturity. The high anthocyanin content, along with the potential health benefits of E. brasiliensis fruits, has led to increased interest in their use as natural food colorants and functional food ingredients [135]. However, further research is needed to fully understand the stability and bioavailability of the anthocyanins and other bioactive compounds in the fruit.

4. Final Considerations

This study reviewed the potential of several plant sources, including roots, flowers, leaves, and fruits, for obtaining natural dyes. These materials, rich in bioactive compounds such as anthocyanins, betalains, and carotenoids, not only provide natural coloring but also offer functional properties like antioxidant, anti-inflammatory, and antimicrobial activities. This review highlighted their potential applications in food, cosmetic, pharmaceutical, and textile industries. Despite the growing interest in natural dyes, challenges related to their stability, agronomic factors, climatic and physiological conditions, and extraction efficiency continue to limit their commercial use. However, advancements in extraction technologies have improved the applicability of these compounds. Additionally, utilizing underexplored plant sources presents a strategic opportunity to diversify dye production, reduce reliance on traditional sources, and promote more sustainable practices.