Crop Productivity, Phytochemicals, and Bioactivities of Wild and Grown in Controlled Environment Slender Amaranth (Amaranthus viridis L.)

Abstract

Amaranthus viridis L. is a wild edible plant that occasionally is cultivated as an alternative crop because of its interest as a functional food and its adaptation to high-saline soils. In this work, leaves from A. viridis were compared with their grown in controlled environment (GCE) counterparts in a soilless system at electrical conductivities (EC) and different light exposures for assessing growth parameters, moisture, total phenolic and total flavonoid content, phenolic compound profiles, vitamin C, antioxidant activity, and antiproliferative activity against the HT–29 human colorectal cancer cell line. The highest biomass production was obtained using EC of 2.5 dS m⁻¹ and the AP67 Milk LED lamp. Vitamin C in wild samples ranged from 83.1 to 104.9 mg 100 g⁻¹ fresh weight (fw), and in GCE ones, it ranged from 112.3 to 236.7 mg 100 g⁻¹ fw. Measured by the DPPH and ABTS assays, the antioxidant activity was higher in wild than in GCE plants: the ranges for wild samples were in the 1.8–4.9 and 2.0–3.9 mmol of Trolox Equivalent (TE) 100 g⁻¹ dry weight (dw) ranges, and for GCE ones in the 1.3–1.9 and 1.5–2.2 mmol TE 100 g⁻¹ dw ranges, respectively. As for phenolic compounds, in wild samples, the range was from 14.65 to 22.70 mg 100 g⁻¹ fw, and these amounts were much higher than those found in their GCE counterparts, in which the range was from 2.58 to 5.95 mg 100 g⁻¹ fw. In wild plants three compounds, namely trans-p-coumaric acid, isorhamnetin-3-O-glucoside, and nicotiflorin, accounted for more than half of the total quantified phenolic compounds. The MTT assay revealed concentration- and time-dependent inhibitory effects on HT–29 cells for all checked extracts. Cancer cells were less influenced by extracts from GCE plants, which showed higher GI₅₀ compared to wild plants. This work improves knowledge on the growth parameters, phytochemical profiles, and biological activities of wild and GCE A. viridis.

1. Introduction

Wild edible plants (WEPs) are indigenous species that thrive and propagate naturally in their native ecosystems without human cultivation. Since ancient times, humans have harvested WEPs, incorporating them into their diets and traditional culinary practices. Serving as vital constituents of local diets in various regions worldwide, WEPs contribute to dietary diversity, enhancing nutritional intake for communities dependent on them. Moreover, certain food plants are valued not only for sustenance but also for their perceived health benefits. Many of these species are employed in traditional herbal medicine, serving as remedies for various ailments in folk phytotherapy [1,2].

Slender amaranth (Amaranthus viridis L.) is native to South and Central America. Today, its range covers warm regions of Africa, Southeast Asia, the Americas, and Europe. The leaves and shoots of this WEP are collected from the wild and cultured for sale in markets for home consumption as a cooked, steamed, or fried vegetable. It grows well during drought, contains valuable nutrients, and can be adapted to different agronomic variables [3,4]. A. viridis is used in folk medicine due to its antipyretic and analgesic properties, as well as in pain and fever treatments. In addition, it shows antioxidant, antimicrobial, hepatoprotective, anti-nociceptive, anti-inflammatory, hypolipidemic, antihyperglycemic, anthelmintic, antiphytopathogenic, and antidiabetic properties [5]. Previously, the leaves of this plant have been reported to be a good source of protein, vitamin C, α-linolenic acid (ALA, 18:3n-3), fibre, and minerals [6,7,8]. However, A. viridis contains some antinutrients such as oxalic acid and nitrates [9]. Recently, the leaves were found to be a good source of nutrients, pigments, minerals, vitamins, phenolics, and flavonoids, having good antioxidant properties [10]. Moreover, the bioaccessibility of proteins, phenolics, flavonoids, and antioxidant activity of the leaves and other organs were reported as suitable for optimal nutrition [11]. However, the phenolic and carotenoid profiles and antitumour activities were not tested. Recently, the nutritional and antioxidant potential of four Amaranthus species (A. tricolor, A. lividus, A viridis, and A. spinosus) was checked by Sarker et al. [12]. The four species were classified as good sources of chlorophylls, betaxanthin, betacyanin, and betalain, while A. viridis contains a low number of flavonols, i.e., quercetin, isoquercetin, hyperoside, rutin (quercetin 3-O-rutinoside), and kaempferol, which accounted for ~2.16 mg 100 g⁻¹ on fw.

In A. viridis and most vegetables, the biosynthesis and accumulation of phytochemicals are intricately influenced by the soil composition and climatic conditions prevailing during their growth. Nutrient uptake and the production of bioactive compounds are typically responsive to both biotic and abiotic stresses, including salinity levels and light radiation. Therefore, controlled cultivation in growth chambers has emerged as a suitable method that offers clear advantages, including enhanced productivity, uniformity of products, and bolstered food security, in contrast to the reliance on wild specimens for human consumption [13].

Furthermore, light exposure and its spectrum play crucial roles in plant development and metabolism [14]. For instance, LED lamps offer advantages such as longevity, minimal heat emission, cost-effectiveness, and the ability to provide irradiation with specific wavelengths compared to other light sources. Red light usually promotes leaf expansion, while blue light enhances total phenolic content (TPC) and antioxidant capacity [15]. In this regard, researchers checked the influence of different LED lights on wild and GCE Ice Plant (Mesembryanthemum crystallinum L.); L8 NS1 and L8 AP67 lamps induced a positive response in comparison with white-light ones on plants grown and plant mass, TPC, and antioxidant activity of leaves [16].

Amaranthus spp. are leafy vegetables extensively acclimated to diverse cultivation conditions thanks to the various stresses they can face, such as salinity [17]. Salinity stress typically induces a rise in the quantity and quality of natural antioxidants through diverse factors, such as physiological, environmental, ecological, biological, biochemical, and evolutionary processes [18]. Nevertheless, the synergistic impact of salinity and light quality on the phenolic profile and bioactivities of A. viridis remains unexplored. In this context, finding the best culture conditions to enhance the concentration of bioactive compounds in cultivated GCE plants could improve the functional value of this vegetable.

Despite the good nutritional qualities of A. viridis, a comprehensive study about bioactive compounds and bioactivities of both GCE and wild plants has not yet been carried out. Therefore, this work was accomplished to unravel the nutritional quality of A. viridis and to check its aptitude for use as a vegetable. To achieve this goal, the development of plants under controlled culture variables was analysed, and the derived phytochemical composition and bioactivities were recorded for comparison with their wild counterparts.

2. Materials and Methods

2.1. Solvents and Reagents

Unless otherwise specified, all solvents and reagents used in this study were purchased from Merck (Madrid, Spain).

2.2. Samples and Growth Conditions

Two independent experiments were carried out. The first one used four treatments with different electrical conductivities (ECs) in the nutrient solution, 1.5 (CT1), 2.5 (CT2), 3.5 (CT3), and 4.5 (CT4) dS m⁻¹. The second is from different lighting conditions, where the same intensity and four different spectra were applied (Supplementary Figure S1). Information regarding A. viridis samples is shown in

Table 1. Data on the status, harvesting location, and cultivation parameters of the A. viridis samples focused on this work.

Sample Code	Status	Location	Electrical Conductivity of the Nutrient Solution/Soil of Collection (dS m−1)	Lamp Type
WC	Wild	Calaburras, Málaga (36.507777, −4.635555)	7.0	-
WT	Wild	El Toyo, Almería (36.837729, −2.327154)	4.0	-
WU	Wild	Almería University (36.831494, −2.401189)	2.1	-
CT1	GCE a	Growth chamber, University of Almería	1.5	L18 T8 Roblan®
CT2	GCE	Growth chamber, University of Almería	2.5	L18 T8 Roblan®
CT3	GCE	Growth chamber, University of Almería	3.5	L18 T8 Roblan®
CT4	GCE	Growth chamber, University of Almería	4.5	L18 T8 Roblan®
LT1	GCE	Growth chamber, University of Almería	2.5	L18 T8 Roblan®
LT2	GCE	Growth chamber, University of Almería	2.5	L18 AP67 Valoya®
LT3	GCE	Growth chamber, University of Almería	2.5	L18 NS1 Valoya®
LT4	GCE	Growth chamber, University of Almería	2.5	L18 NS12 Valoya®

^a Grown in a Controlled Environment.

. In both experiments, the plants were grown in a soilless culture system with LED lamps at the University of Almeria, in controlled growth chambers (10 × 2.5 m) between April and May 2023. The photoperiods were 16/8 h (day/night) at a temperature of 20–22 °C and 80–85% relative humidity and 250 μmol⁻² s⁻¹ photosynthetic photon flux density (400–700 nm). Growth, fertigation, and lighting conditions applied to GCE plants are detailed in Supplementary File S1. The composition of the nutrient solutions is detailed in the Supplementary Table S1. The pH of the nutrient solutions of both trials was maintained at 5.8 by adding nitric acid.

Once in the laboratory, samples were labelled, weighed, measured, and placed in a glass desiccator until analysis. Plant leaves (2 g) were placed in a forced air oven at 105 °C until constant weight to determine the moisture content.

2.3. Extraction and Quantification of Vitamin C

The analyses of vitamin C (L-ascorbic acid) were accomplished following the procedure of Volden et al. [19], with minor adjustments. The full protocol for this determination is given in Supplementary File S1. The analysis of vitamin C was effected using a High-Performance Liquid Chromatograph (HPLC) Finnigan Surveyor chromatograph equipped with a diode-array detector (DAD) and a reverse-phase C18 column (Luna^® Omega, 250 mm × 4.6 mm i.d., 3 µm particle size, from Phenomenex, Torrance, CA, USA), (HPLC-DAD system). The quantification of this vitamin was effected through external calibration, and results are given as mg of ascorbic acid per 100 g of fresh weight (fw).

2.4. Extraction of Phenolic Compounds

This methodology is detailed in Supplementary File S1. Extraction and analysis of phenolic compounds from leaves was performed as described by Lyashenko et al. [20].

2.5. Determination of Total Phenolic and Total Flavonoid Content

The total phenolic content (TPC) was evaluated using the Folin–Ciocalteu (F-C) assay [21]. This protocol is provided in Supplementary File S1. Results were reported as mg of Gallic Acid Equivalents (GAEs) by 100 g of fw and were obtained using a gallic acid standard curve. Total flavonoid content (TFC) was assessed using the protocol proposed by Zou et al. [22], as described in Supplementary File S1. Results were expressed as mg of Quercetin Equivalents (QEs) per 100 g fw.

2.6. Determination of the Antioxidant Activity

The extraction of leaves was accomplished following the procedure proposed by Forbes–Hernández et al. [23], which is included in Supplementary File S1. The antioxidant activity was measured using the ABTS method, which uses an ABTS^•+ radical solution (2.2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)) in ethanol (2.45 mM) [24]. The DPPH method was accomplished according to the Skenderidis et al. [25] protocol (Supplementary File S1). Results for both ABTS^•+ and DPPH methods are expressed as mmol of Trolox Equivalent (TE) per 100 g of dry weight (dw).

2.7. Characterization of Phenolic Compounds by HPLC-DAD

This procedure is fully detailed in Supplementary File S1. HPLC-DAD analyses of phenolic compounds were conducted using the instrument described in Section 2.3. Compounds were separated employing a gradient elution using acidified water (1% acetic acid) (A) and acetonitrile (B) as the mobile phase at 25 °C. The total running time was 105 min. The HPLC-DAD parameters for analysis of phenolic-rich extracts of A. viridis samples are detailed in Supplementary Table S2. Quantification of the compounds was accomplished by external calibration curves using pure standards. A typical HPLC-DAD chromatogram is shown in Figure 1.

2.8. Characterization of Phenolic Compounds by LC-MS

This methodology is fully detailed in Supplementary File S1, while the LC-MS parameters for analysis of phenolic-containing extracts are detailed in Supplementary Table S3. This table also contains the basis for the structure elucidation of all compounds based on m/z of the parent molecular ion and fragments. The chromatographic separation was performed on a Thermo Fisher Scientific Transcend 600 LC (Thermo Scientific TranscendTM, Thermo Fisher Scientific, San Jose, CA, USA) using a Hypersil Gold column (250 × 4.6 mm, 5 µm). A flow rate of 0.65 mL min⁻¹ was set. The compounds were separated with gradient elution using aqueous acetic acid (acetic acid:H₂O, 1:99, v/v) (A) and methanol (B) as eluents at ambient temperature.

The LC system is coupled to a single MS Orbitrap Thermo Fisher Scientific (ExactiveTM, Thermo Fisher Scientific, Bremen, Germany) using an electrospray interface (ESI) (HESI-II, Thermo Fisher Scientific, San Jose, CA, USA) in positive and negative ion mode. The mass spectra were acquired employing alternating acquisition functions: (1) full MS, ESI+, without fragmentation; (2) all-ion fragmentation (AIF), ESI+, with fragmentation (HCD on); (3) full MS, ESI, using the above-mentioned settings; and (4) AIF, ESI, using the settings explained for (2). The mass range in the full scan experiments was set at m/z 50–1000. LC chromatograms were acquired using the external calibration mode, which were processed using XcaliburTM version 3.0, with Qualbrowser and Trace Finder 4.0 (Thermo Fisher Scientific, Les Ulis, France). An unknown analysis was carried out with Compound DiscovererTM version 2.1.

2.9. Antitumor Assays

This methodology is fully detailed in Supplementary File S1. The antiproliferative activity of phenolic-containing hydroalcoholic extracts (methanol:water, 60:40, v/v) of samples was evaluated by the MTT assay on the HT-29 human colon cancer cell line and the CCD-18 human colonic myofibroblast cell line, as described by Lyashenko et al. [20]. The Selectivity Index was calculated as indicated in Supplementary File S1.

2.10. Statistical Analysis

Each sample underwent triplicate analyses. The data were evaluated for normality employing a Shapiro–Wilk test and subjected to a one-way ANOVA. Means were compared using Duncan’s Multiple Range Test, and p < 0.05 was considered statistically significant. These statistical analyses were performed using Statgraphics^© Centurion XVI software (StatPoint Technologies, Warrenton, VA, USA). Correlation studies were conducted using Python Language Reference, v. 3.11 (Python Software Foundation, http://www.python.org, accessed on 12 February 2024).

3. Results

3.1. Effect of Salinity and Light on Growth Parameters in GCE A. viridis

3.1.1. Monitoring Fertigation Parameters

The drainage volume fraction remained constant between 0.2 and 0.3 in both experiments. In the EC experiment, the ECs of drainage for the crop showed a general increasing trend and reached levels higher than two units above the fertigation value. This indicates that the nutrient concentration in the cultivation medium was rising over time, potentially due to the accumulation of salts or nutrients not being fully absorbed by the plants (Supplementary Figure S2a). Data indicate that the mean drainage values varied significantly and were influenced by different EC levels, with the highest drainage values observed at ECs from 3.5 to 4.5 dS m⁻¹ (Supplementary Figure S2b). All values of the treatments were within the acceptable and desired limits for the crop, with an EC value 1–2 dS m⁻¹ above the supplied fertigation, suggesting that this crop is tolerating EC variations without adverse effects and is still within the crop’s tolerance range [26,27].

During a three-week crop period, the drainage pH varied significantly among the treatments, with the highest pH recorded at 0.6 units above the fertigation pH of 5.8, resulting in a peak pH of 6.4 (Supplementary Figure S2c). For the CT1 treatment (nutrient solution with an EC of 1.5 dS m⁻¹), the mean drainage pH over the crop cycle was higher than that of other treatments, with an average pH of 6.4 (Supplementary Figure S2d). pH levels up to one unit above the fertigation pH value are expected under vegetative growth conditions in A. viridis plants [27].

The results of the lighting experiment indicate a general increase in drainage EC values in all treatments as cultivation time increases, except for one specific treatment, LT4 (L18 NS12 Valoya^®-agricultural LED light-), which shows a 20% lower average EC compared to the other treatments (Supplementary Figure S3a). Except for the LT3 treatment in the first week, there was no statistically significant difference in drainage pH across the weeks, with an average value of 6.1 dS m⁻¹ (Supplementary Figure S3c,d). There was a statistically significant difference in fertigation uptake in the EC experiment (Figure 2a), with the highest uptake occurring at EC levels ranging from 1.5 to 2.5 dS m⁻¹.

3.1.2. Fertigation Uptake and Growth Parameters

There was a statistical difference in fertigation uptake in the EC experiment (Figure 2a), with the highest uptake occurring at EC levels ranging from 1.5 to 2.5 dS m⁻¹. However, the highest values of nitrate and potassium uptake were obtained at an EC of 3.5–4.5 dS m⁻¹ for nitrate and 4.5 dS m⁻¹ for potassium, likely due to their higher concentration in the nutrient solution (Figure 2b,c), which is consistent with previous reports [28]. Treatments with EC levels exceeding 2.5 dS m⁻¹ resulted in a notable reduction in fresh and dry weight growth in A. viridis plants (Figure 2d), suggesting that this value indicates a threshold effect. According to the classic model by Maas and Hoffman [29], a loss ratio greater than 20% post-threshold marks the plant as moderately sensitive to salinity.

The uptake of potassium and nitrate in A. viridis followed a trend similar to water absorption, with notable differences across treatments (Figure 3a–c). The LT2 treatment, designed specifically for horticulture, recorded the highest water uptake compared to other light treatments (LT3 and LT4) and the control with standard LED lighting (LT1). Nitrate uptake also mirrored the trend noted with water absorption, with the LT2 treatment resulting in the highest nitrate absorption. However, the LT4 treatment recorded the lowest nitrate uptake, with values more than 40% lower than the LT2 treatment. This is in contrast to findings by Peçanha et al. [30], who reported no significant differences in nitrate uptake when using the same lamps for rooting lavender plants.

The lowest values of potassium and nitrate uptake (higher than 40%) were found in the control treatment (LT1) for potassium and in the LT4 treatment for nitrate, in contrast to the results published by Peçanha et al. [30], who found no significant differences using the same lamps for the rooting of lavender plants. The higher biomass is directly related to the higher water uptake in A. viridis plants (Figure 3d). The highest fresh and dry yield was recorded for treatment LT2. The highest water absorption was also recorded under the LT2 treatment, which was designed specifically for horticulture. This was significantly higher compared to other treatments with agricultural lights (LT3 and LT4) and the control with standard LED lighting (LT1).

3.2. Moisture

In wild samples, moisture ranged from 81.0 in WT to 85.7 g 100 g⁻¹ in WC (

Table 2. Moisture, antioxidant activity, vitamin C, and total phenolic compounds of A. viridis samples ^1,2,3,4.

		Antioxidant Activity
Samples/Codes	Moisture g 100 g−1	DPPH mmol TE 100 g−1 dw	ABTS mmol TE 100 g−1 dw	Vitamin C mg 100 g−1 fw	TPC mg GAE 100 g−1 fw	TFC mg QE 100 g−1 fw
Wild plants
WC	85.7 ± 0.7 a	4.9 ± 0.2 a	3.9 ± 0.3 c	83.1 ± 2.9 i	209.3 ± 10.4 g	158.2 ± 6.5 e
WT	81.0 ± 1.6 c	2.5 ± 0.1 b	2.0 ± 0.1 c	104.9 ± 0.4 gh	330.0 ± 14.3 a	212.0 ± 9.3 ab
WU	81.9 ± 0.6 bc	1.8 ± 0.1 c	3.1 ± 0.2 b	103.5 ± 3.3 h	276.4 ± 13.9 bc	198.5 ± 6.4 bc
Grown in a controlled environment plants
Saline treatments
CT1 (1.5 dS m−1)	80.5 ± 0.1 c	1.3 ± 0.0 f	1.5 ± 0.2 c	200.5 ± 0.7 c	213.6 ± 5.9 g	159.4 ± 7.4 de
CT2 (2.5 dS m−1)	81.9 ± 0.2 bc	1.6 ± 0.1 cde	1.7 ± 0.1 c	210.4 ± 2.0 b	248.4 ± 14.7 def	184.4 ± 5.3 c
CT3 (3.5 dS m−1)	84.0 ± 2.4 abc	1.7 ± 0.2 cd	2.2 ± 0.6 c	229.6 ± 2.5 a	242.3 ± 6.6 f	186.6 ± 6.1 c
CT4 (4.5 dS m−1)	83.5 ± 2.4 abc	1.9 ± 0.0 c	2.1 ± 0.3 c	236.7 ± 8.3 a	270.4 ± 16.9 cde	213.1 ± 14.5 ab
Light treatments
LT1 (L18 T8)	84.8 ± 0.7 ab	1.6 ± 0.2 cde	2.0 ± 0.2 c	112.3 ± 5.2 fg	272.0 ± 14.8 cd	178.8 ± 10.1 cd
LT2 (L18 AP67)	80.4 ± 2.4 c	1.4 ± 0.1 de	1.5 ± 0.2 c	114.1 ± 1.8 ef	303.5 ± 11.5 ab	229.3 ± 15.1 a
LT3 (L18 NS1)	82.8 ± 1.7 abc	1.7 ± 0.4 cde	1.8 ± 0.6 c	120.9 ± 4.5 de	268.8 ± 14.6 cdef	222.3 ± 2.8 a
LT4 (L18 NS12)	83.1 ± 1.9 abc	1.4 ± 0.1 de	1.8 ± 0.5 c	125.3 ± 4.3 d	243.1 ± 10.6 ef	197.5 ± 7.5 bc
α-Tocoferol	-	17.6 ± 0.6	8.8 ± 0.5	-	-	-
Ascorbic acid	-	23.4 ± 1.4	10.5 ± 0.2	-	-	-
Caffeic acid	-	22.2 ± 0.4	10.4 ± 0.3	-	-	-

¹ Data represent means ± standard deviation of samples analysed in triplicate. ² Differences in moisture, antioxidant activity, vitamin C, and phenolic content of the various samples were tested according to one-way ANOVA followed by Duncan’s Multiple Range Test. ³ Whitin a column, means followed by different letters are significantly different at p < 0.05. ⁴ Results are expressed as Gallic Acid Equivalents (GAEs), Quercetin Equivalents (QEs), and Trolox Equivalents (TEs).

). Mean moisture values for GCE plants under different salinity conditions ranged from 80.5 to 84.0 g 100 g⁻¹ in CT1 and CT3, and the moisture of GCE plants under different light treatments varied from 80.4 in LT2 to 84.8 g 100 g⁻¹ with LT1 lamps (Table 2).

3.3. Vitamin C

Table 2 details vitamin C concentrations in various A. viridis samples, including wild and GCE plants exposed to different saline and light treatments. Vitamin C ranged from 83.1 in WC to 236.7 mg 100 g⁻¹ fw in CT4.

3.4. Antioxidant Activity

This is detailed in Table 2. DPPH and ABTS values ranged from 1.3 and 1.5 (CT1) to 4.9 and 3.9 (WC) mmol TE 100 g⁻¹ dw. Pure compounds checked by the DPPH methodology had values from 17.6 (α–tocopherol) to 23.4 mmol TE 100 g⁻¹ (vitamin C), and for the ABTS^•+ assay, values varied between 8.8 (α–tocopherol) and 10.5 mmol TE 100 g⁻¹ (vitamin C).

3.5. Total Phenols and Flavonoids

Table 2 informs the total phenolic content (TPC) and total flavonoid content (TFC) in the various A. viridis samples. TPC ranged from 209.3 in WC to 330.0 mg GAE 100 g⁻¹ fw in WT (Table 2). TFC also showed significant differences, with the highest value recorded in the LT2 sample (229.3) and the lower one obtained for WC samples (158.2 mg QE 100 g⁻¹ fw).

3.6. Phenolic Compound Profiles

Two LC systems were used for the qualitative and quantitative analysis of phenolic compounds. The profiles of phenolic compounds quantified through the HPLC–DAD system are shown in

Table 3. Phenolic compounds of methanol–water extracts of A. viridis samples (mg 100 g⁻¹ fw) ^1,2,3.

Species/Codes	Gallocatechin (−) 4	3,4- dihydroxybenzoic Acid (Protocatechuic Acid)	4-hydroxybenzoic Acid	Trans-p-coumaric Acid	Quercetin 3-O-rutinoside (Rutin)	Trans-ferulic Acid	Quercetin-3- O-glucoside (Isoquercetin)
Wild plants
WC	0.13 ± 0.02 e	0.67 ± 0.06 b	1.10 ± 0.05 b	2.80 ± 0.19 a	0.11 ± 0.03 c	0.12 ± 0.01 de	0.15 ± 0.02 c
WT	0.59 ± 0.09 a	1.20 ± 0.10 a	0.81 ± 0.04 cd	2.89 ± 0.22 a	3.22 ± 0.22 a	0.21 ± 0.02 bc	1.23 ± 0.09 a
WU	0.31 ± 0.09 bcd	0.50 ± 0.09 c	1.39 ± 0.07 a	2.03 ± 0.21 b	0.78 ± 0.04 b	0.25 ± 0.05 ab	0.46 ± 0.02 b
Grown in a controlled environment plants
Saline treatments
CT1	0.30 ± 0.02 cd	<LOQ	0.68 ± 0.08 e	0.20 ± 0.03 d	<LOQ	0.17 ± 0.01 cd	<LOQ
CT2	0.34 ± 0.02 bc	<LOQ	0.70 ± 0.07 de	0.20 ± 0.04 d	<LOQ	0.22 ± 0.03 bc	<LOQ
CT3	0.29 ± 0.09 cd	<LOQ	0.52 ± 0.06 f	0.10 ± 0.01 d	<LOQ	0.20 ± 0.03 bc	0.10 ± 0.01 c
CT4	0.18 ± 0.02 de	<LOQ	0.33 ± 0.02 g	0.11 ± 0.02 d	<LOQ	0.14 ± 0.02 de	0.11 ± 0.02 c
Light treatments
LT1	0.30 ± 0.02 cd	<LOQ	0.10 ± 0.02 h	0.78 ± 0.06 c	<LOQ	0.11 ± 0.02 e	0.11 ± 0.0 c
LT2	0.44 ± 0.08 b	<LOQ	1.05 ± 0.06 b	0.20 ± 0.02 d	0.14 ± 0.01 c	0.10 ± 0.02 e	0.12 ± 0.01 c
LT3	0.32 ± 0.08 bc	<LOQ	0.88 ± 0.07 c	0.10 ± 0.00 d	<LOQ	0.28 ± 0.03 a	0.10 ± 0.01 c
LT4	0.30 ± 0.04 cd	<LOQ	0.72 ± 0.05 de	0.10 ± 0.01 d	<LOQ	0.20 ± 0.03 bc	0.10 ± 0.01 c
Species/Codes	Apigenin-7-O- glucoside (Apigetrin)	Apigenin-7-O- Glucuronide 5 (Scutellarin A)		Isorhamnetin-3-O-glucoside 5	Kaempferol-3-O- rutinoside 5 (Nicotiflorin)		Total Identified Phenolics
Wild
WC	0.40 ± 0.05 c	0.41 ± 0.05 bc		3.33 ± 0.25 b	5.17 ± 0.22 b		14.38 ± 0.40 c
WT	0.84 ± 0.09 a	0.96 ± 0.02 a		5.84 ± 0.30 a	4.52 ± 0.15 c		22.31 ± 0.50 a
WU	0.65 ± 0.08 b	0.48 ± 0.03 b		3.11 ± 0.24 b	8.58 ± 0.25 a		18.54 ± 0.45 b
Grown in a controlled environment plants
Saline treatments
CT1	0.36 ± 0.08 cd	0.24 ± 0.01 def		0.17 ± 0.01 c	1.18 ± 0.18 fg		3.32 ± 0.23 f
CT2	0.35 ± 0.09 cd	0.19 ± 0.01 efg		0.18 ± 0.01 c	0.66 ± 0.09 hi		3.84 ± 0.18 e
CT3	0.26 ± 0.09 cde	0.25 ± 0.07 de		0.35 ± 0.06 c	1.55 ± 0.10 e		3.58 ± 0.22 ef
CT4	0.21 ± 0.08 de	0.15 ± 0.05 g		0.37 ± 0.05 c	0.53 ± 0.02 i		2.08 ± 0.15 g
Light treatments
LT1	0.14 ± 0.01 e	0.27 ± 0.01 d		0.14 ± 0.01 c	0.51 ± 0.02 i		3.47 ± 0.14 ef
LT2	0.37 ± 0.09 cd	0.36 ± 0.04 c		0.42 ± 0.06c	2.02 ± 0.15 d		5.31 ± 0.22 d
LT3	0.25 ± 0.04 cde	0.17 ± 0.01 fg		0.21 ± 0.03c	1.30 ± 0.14 ef		3.61 ± 0.19 ef
LT4	0.34 ± 0.06 cd	0.17 ± 0.01 fg		0.32 ± 0.03c	0.92 ± 0.09 gh		3.16 ± 0.19 f

¹ Data represent means ± SD of samples analysed in triplicate. ² Differences in phenolic amounts were tested according to one-way ANOVA followed by Duncan’s test. ³ In a column, means followed by different superscript letters are significantly different at p < 0.05. ⁴ Gallic Acid Equivalents; ⁵ apigenin-7-O-glucoside equivalents; <LOQ: below the limit of quantification.

, while the LC–MS system results are detailed in Supplementary Table S4. Chromatograms were screened at 254, 280, and 320 nm (Supplementary Table S2), revealing robust molar extinction coefficients. The identification process was based on comparing the retention times (Rt) and absorption spectra of all peaks across the chromatograms with those of pure standards. The HPLC–DAD parameters used for the analysis of the phenolic-rich extracts of A. viridis samples, including linearity range, regression equations, limits of detection (LOD), limits of quantification (LOQ), and compound recoveries, are provided in Supplementary Table S2. Precision and injection repeatability tests demonstrated commendable precision in both peak area (standard deviation <1%) and peak Rt (±2%).

Phenolic compounds quantified by the HPLC-DAD system were hydroxycinnamic acids (trans-ferulic and trans-p-coumaric acids), benzoic acid derivatives (protocatechuic and 4-hydroxybenzoic acids), and flavonoids. The trans-ferulic acid was between 0.10 (LT2) and 0.28 mg 100 g⁻¹ (LT3); trans-p-coumaric acid was between 0.10 (CT3, LT3, and LT4) and 2.89 mg 100 g⁻¹ (WT); protocatechuic acid ranged from 0.50 (WU) to 1.20 (WT) mg 100 g⁻¹; and 4-hydroxybenzoic acid was from 0.10 (LT1) to 1.39 mg 100 g⁻¹ (WU). As for flavonoids, gallocatechin (−) was between 0.13 (WC) and 0.59 mg 100 g⁻¹ (WT); rutin was between 0.11 (WC) and 3.22 mg 100 g⁻¹ (WT); isoquercetin (quercetin-3-O-glucoside) was from 0.10 (CT3, LT3, and LT4) to 1.23 mg 100 g⁻¹ (WT); apigetrin (apigenin-7-O-glucoside) ranged from 0.14 (LT1) to 0.84 mg 100 g⁻¹ (WT); scutellarin A (apigenin-7-O-glucuronide) was between 0.15 (CT4) and 0.96 mg 100 g⁻¹ (WT); isorhamnetin-3-O-glucoside was from 0.14 (LT1) to 5.84 mg 100 g⁻¹ (WT); and nicotiflorin (kaempferol-3-O-rutinoside) was between 0.51 (LT1) and 8.58 mg 100 g⁻¹ (WU). TPC ranged from 2.08 in CT4 to 22.31 mg 100 g⁻¹ in WT.

Compounds identified in A. viridis samples through HPLC-DAD were confirmed by LC-MS (Supplementary Table S3). In addition to the compounds identified by HPLC-DAD, the LC-MS system allowed the detection of other compounds for which standards were unavailable. These compounds were tentatively identified in the HPLC-DAD chromatogram based on retention time and absorbance (nm) and quantified using equivalent compounds, as explained in Table 3. Such phenolics were gallocatechin (−), isoquercetin, isorhamnetin-3-O-glucoside, and nicotiflorin (Table 3). Moreover, other phenolic compounds were identified based on their m/z ions and fragments, albeit in minimal quantities (Supplementary Table S4), and lacked clear peaks in the HPLC-DAD chromatogram. Considering that all prominent peaks in the HPLC-DAD chromatogram were successfully assigned, the unquantified compounds occurred in minor amounts (<LOQ), and these were 5-O-caffeoyl-shikimic acid, chlorogenic acid, epigallocatechin (−), DL-p-hydroxyphenyllactic acid, caffeic acid, lithospermic acid, sinapic acid, vanillic acid, quercimeritrin (quercetin-7-O-glucoside), and naringenin (5,7,4′-trihydroxyflavanone).

3.7. Antiproliferative Activity of A. viridis Extracts

The MTT assay (Figure 4) was accomplished to check the antiproliferative activity of the methanol-water extracts from A. viridis on HT-29 human colorectal cancer cells. Extracts from wild and cultured samples obtained under different light and salinity conditions were checked. The effects of extracts on cell viability after 48 and 72 h of treatment are shown in Figure 4A,B. The extracts from WT, WU, CT3, and LT3 at 1000 µg mL⁻¹ and after 72 h of exposure to cells resulted in reductions of 7.8, 10.1, 47.9, and 43.8% in cancer cell viability compared to the control group (without extract addition). Figure 4C illustrates the GI₅₀ (the dose of extracts that inhibited cell growth by 50%) of more active samples, along with those of two pure phenolic compounds occurring in samples. After 72 h of incubation, WT, WU, CT3, and LT3 showed GI₅₀ values of 360, 400, 950, and 850 µg mL⁻¹, respectively, whereas caffeic acid and ferulic acid showed GI₅₀ values of 500 and 40 µg mL⁻¹. The positive control doxorubicin had a GI₅₀ of 3 µg mL⁻¹. The SI of HT-29 versus normal CCD-18 cells was assessed after 72 h of cell exposure to extracts and pure compounds having GI₅₀ < 400 µg mL⁻¹, and this index was 2.5 (WT) and 3.1 (WU) for A. viridis extracts, while for ferulic acid and doxorubicin, it was 4 and 15.

3.8. Correlation Studies

Figure 5 shows the correlations between the antioxidant activity, growth parameters, and bioactive compounds using data from all analysed A. viridis samples.

4. Discussion

4.1. Effect of Salinity and Light on Growth Parameters in GCE A. viridis

4.1.1. Monitoring Parameters of Fertigation

Drainage volume fraction, EC, and pH are widely used for monitoring, control, and feedback of nutrient solution management and fertigation [27,31,32,33]. The mean EC values of the drainage in experiment 1 are within acceptable limits, considering one or two units of dS m⁻¹ above the value applied in the nutrient solution. These standard conditions (expressed through EC) indicate that there was higher metabolic activity in root uptake (especially potassium and nitrate) proportionally to the water taken up [32,34,35].

The effect of pH on growth and nutrient uptake for horticultural plants was established long ago, e.g., [36,37], and yet it is accepted today, e.g., [38,39]. The pH of the drainage water varied by 0.5 to 0.7 units above the initial value of 5.8. According to Ferrón-Carrillo et al. [40], the expected pH variation for vegetative growth conditions in plants such as A. viridis can be up to one unit higher, indicating that the observed pH changes were within acceptable limits for plant growth. In the lighting experiment, the EC of drainage showed higher values for LT1, LT2, and LT3 lamps. However, there was no difference in pH values. This situation differs from others reported by Ferrón-Carrillo et al. [39] for the same LED lamps, where higher growth and yield in bell pepper and tomato plants were found using agricultural LED lamps concerning the control (LT1).

4.1.2. Fertigation Uptake and Growth Parameters

As for the EC experiments, results show that treatments with EC levels above 2.5 dS m⁻¹ resulted in reduced water uptake and growth (fresh and dry weight) in A. viridis. This indicates the plant’s sensitivity to salinity, similar to the sensitivities observed in lettuce and tomato by Cunha-Chiamolera et al. [26]. Water uptake, a parameter highly correlated with growth and yield [40,41], showed significant reductions at higher salinity levels. In similar growing conditions for the ice plant, Rincón-Cervera et al. [16] found that the optimum electrical conductivity (EC) levels were well above 2.5 dS m⁻¹. While this plant is considered very tolerant to salinity, A. viridis behaved like a sensitive plant under these conditions.

Potassium and nitrate are the main nutrient cation and anion uptake for all higher plants, making them suitable indicators of adequate mineral uptake in a crop [36,39,42]. The trends recorded concerning potassium and nitrate uptake across different EC treatments underscore their importance as key nutrients for monitoring plant growth and nutrient uptake efficiency.

The effect of nitrate and potassium uptake on their transport in the xylem was previously described by Gallegos-Cedillo et al. [28] for tomato plants. They found that potassium and nitrate uptake increased with increasing concentrations in the nutrient solution from 3.5 to 4.5 dS m⁻¹. Higher nutrient uptake is generally related to increased availability of these nutrients in the fertigation, leading to greater uptake by the plant [27,28].

The spectral composition of light not only influences biomass growth but also affects the functionality of stomata and the overall efficiency of water use of plants [16]. Concerning the lighting experiment, the treatment with LT2 (AP67 lamps) resulted in the highest water and nutrient uptake. Spalholz et al. [43] highlight that both the spectral composition and intensity of light are important factors for crop yield, stating that tailored light conditions can enhance various aspects of plant growth and productivity.

Additionally, the NS1 lamps, with a broad spectrum equivalent to sunlight and longer wavelengths in blue light, enhanced plant absorption and growth better than LT1. This underscores the critical role of both the spectral composition and intensity of light in horticulture, as highlighted by Spalholz et al. [43]. Similar results were reported by Haddaji et al. [44], where basil performed better under blue light, while Trigonella foenum-graecum, Anethum graveolens, and Anthriscus cerefolium thrived under red light. These findings align with our observations that specific wavelengths significantly affect plant performance. The LT2 treatment, tailored to horticultural light requirements, demonstrated an approximately 60% improvement in fresh and dry mass compared to the control (LT1). Nájera and Urrestarazu [14] reported that LED light intensity and spectral quality significantly influence vegetable growth.

Water uptake of the nutrients nitrate and potassium showed very different trends. While water uptake had a maximum value coinciding with the optimum production (in fresh and dry weight) for both experiments, the maximum nitrate and potassium uptakes occurred when the contents of these two nutrients in the nutrient solution were increased. The observed correlation between increased water uptake and enhanced yields has been well-documented in soilless cultivation systems for various horticultural crops [33]. This relationship underscores the critical role of adequate water supply in supporting optimal plant growth and biomass production. Conversely, the trend of higher nitrate and potassium uptake with increased nutrient concentrations in the rhizosphere aligns with findings by Gallegos-Cedillo et al. [28].

4.2. Vitamin C

Vitamin C is a water-soluble vitamin that plays a fundamental role in various biological functions of the human body. Collagen synthesis is dependent on its occurrence in tissues. Furthermore, it acts as an antioxidant, protecting cells from free radical damage and improving the immune system [45]. A daily intake of 75–90 mg is recommended for adults, although this amount may vary depending on age, sex, health status, and other individual factors [45].

The results of this study reveal significant variations in vitamin C levels among the various A. viridis samples. Wild samples (WC, WT, and WU) were noted to have less variability in vitamin C levels, ranging from 83.1 to 104.9 mg 100 g⁻¹ fw, compared to GCE ones, ranging from 112.3 (LT1) to 236.7 mg 100 g⁻¹ fw (CT4). This fact could be attributed to differences in environmental and growth conditions. Reduced nutrient availability and exposure to environmental stressors in wild habitats may have contributed to these differences in vitamin C levels. Another study on Amaranthus species such as A. blitum, A. dubius, A. tricolor, A. viridis, and A. thunbergii showed total vitamin C concentrations between 130 and 140 mg by 100 g fw [46], which supports the low variability in vitamin C levels in wild samples. Secondly, a significant effect of abiotic stress treatments such as soil salinity and light intensity was observed in vitamin C concentrations in GCE A. viridis samples. For cultured plants, the higher the EC, the higher the rise in vitamin C concentrations. This suggests an adaptive response to salinity by accumulating this non-enzymatic antioxidant. On the other hand, plants exposed to different lamp types which were grown at 2.5 dS m⁻¹ showed minimal variations in vitamin C concentrations (from 112.3 in LT1 to 125.3 in LT4 mg 100 g⁻¹ fw), thus indicating a minor influence of the light type on the biosynthesis and accumulation of this vitamin.

4.3. Antioxidant Activity

Phenolic compounds act as pivotal agents in alleviating stress induced by reactive oxygen species (ROS) in plants, often displaying a direct association between phenolic content and the antioxidant efficacy within plant extracts [47]. The antioxidant activity was checked using the ABTS and DPPH assays, given their heightened sensitivity in gauging radical scavenging capabilities [13]. Measured by both methodologies, the antioxidant activity was higher in wild than in GCE plants. Through the DPPH and ABTS assays, this activity was in the 1.8–4.9 and 2.0–3.9 mmol TE 100 g⁻¹ dw ranges for wild samples and in the 1.3–1.9 and 1.5–2.2 mmol TE 100 g⁻¹ dw ranges for GCE ones. These results can be explained considering that wild plants are exposed to greater environmental stressing factors (sunlight, temperature changes, etc.), which stimulate the synthesis of antioxidant compounds as a defence mechanism. High-salinity soils induce osmotic stress in plants through the production of ROS. To counteract such compounds, the plants produce antioxidant molecules, which decrease the cytoplasmic osmotic potential, allowing water uptake to detoxify ROS. This mechanism ultimately causes the plants to adapt to salinity stress, and thus, they can continue their vegetative development [48]. Additionally, EC and lighting experiments allowed for assessing the impact of the modified parameters on the antioxidant activity. An improvement in the antioxidant activity measured by both methodologies was noted at increased EC values, which were in the 1.5–4.5 dS m⁻¹ range. Globally, this activity varied from 1.3 to 1.9 (DPPH) and 1.5 to 2.1 (ABTS) mmol TE 100 g⁻¹ dw. These results agree with those of Sarker and Oba [49], who found higher values of antioxidant activity (also measured by the ABTS and DPPH methods) at higher salinity concentrations in Amaranthus leafy vegetables.

4.4. Phenolic Compound Content

TPC and TFC were quite similar in wild plants and in plants GCE under different EC and lamp types. However, within the latter, a small increase in TPC and TFC in parallel to a rise in EC (1.5 to 4.5 dS m⁻¹) was noted, with CT4 samples showing the highest amounts of TPC and TFC. This suggests that salinity may act as a stress factor inducing the synthesis of phenolic compounds in these plants. Conversely, lighting treatments lack a clear influence on TPC and TFC in contrast to salinity ones. As for GCE plants, the higher TPC and TFC values were recorded for LT2 samples. Although it has been suggested that blue and UV light typically stimulate phenol synthesis in plants by regulating gene expression in response to increased reactive oxygen species (ROS) production, this phenomenon has not been extensively validated [15].

4.5. Phenolic Compounds Profiles

The phenolic profiles of all analysed samples were quantified using HPLC-DAD (Table 3). Additionally, compounds identified by LC-MS are detailed in Supplementary Table S4.

In wild samples, phenolics ranged from 14.38 (WC) to 22.31 mg 100 g⁻¹ fw (WT), amounts much higher than those found in their GCE counterparts, in which the range was from 2.08 (CT4) to 5.31 mg 100 g⁻¹ fw (LT2). In wild plants, three compounds, namely trans-p-coumaric acid, isorhamnetin-3-O-glucoside, and nicotiflorin, account for more than half of the total quantified phenolic compounds.

It is necessary to consider that wild samples were collected from environments with different ECs in soils; therefore, the increased synthesis of phenolics cannot be attributed solely to EC, and this situation may be a consequence of wild samples being exposed to more biotic (pathogens, herbivory) and abiotic (sunlight, drought, etc.) stresses that induce the synthesis of phenolic compounds as a plant defence mechanism [50,51].

Concerning GCE samples, rutin and protocatechuic acid occurred at levels below LOD in most cases, and trans-p-coumaric acid, isoquercetin, isorhamnetin-3-O-glucoside, and nicotiflorin reached significantly lower amounts in GCE samples while lacking the remaining compounds, a clear trend considering both plant types. It is worth mentioning that in plants grown under the AP67 lamp, which has a higher proportion of red light, a notable increase in nicotiflorin was obtained. This is in good agreement with findings of Cioć et al. [52] for Myrtus communis, who indicated that phenolic acids were stimulated by red light and inhibited under blue light exposure. The authors suggested that this phenomenon may be attributed to red light’s stimulation of cytokinins in plants, consequently leading to phenolic compound biosynthesis.

Sarker et al. [12] found quercetin (0.44), isoquercetin (0.50), hyperoside (0.13), rutin (0.64), and kaempferol (0.45) in the leaves of A. viridis, and the TPC as a sum of the total peaks area was 2.2 mg 100 g⁻¹ fw. This amount was approximately ten times lower than that obtained in this work for wild samples, although this agrees with the amounts obtained here for GCE plants. Rutin and isoquercetin, the predominant compounds, were also detected in this work, while quercetin and kaempferol were found in glycosylated form; therefore, a good agreement was found between the results of both works, although we reported a total of 11 different compounds, while Sarker et al. [12] indicated 5. House et al. [53] identified ferulic acid, 4-hydroxycinnamic acid, myricetin-3-O-rutinoside, quercetin-3-O-rutinoside, and quercetin in the methanolic extracts of A. viridis leaves, although they did not quantify them. Considering the leaves of other Amaranthus species, rutin, isoquercetin, and nicotiflorin were previously found in A. caudatus by Karamać et al. [54]; protocatechuic acid, rutin, trans-ferulic acid, and nicotiflorin were cited in A. caudatus and A. hypocondriacus by Li et al. [55]. However, 4-hydroxybenzoic acid and isorhamnetin-3-O-glucoside, which reached large amounts in the wild samples analysed here, lack previous reports in the leaves of Amaranthus species. Considering all previous reports, quercetin and its phenolic derivatives are the compounds most frequently found in the leaves of A. viridis and other species of the same genus.

The main phenolics detected in this work develop clear health effects. For instance, p-coumaric acid possesses antioxidant, antimicrobial, anticancer, antiarthritic, and anti-inflammatory properties [56]; isorhamnetin-3-O-glucoside enhances insulin secretion [57]; and nicotiflorin develops anti–atherosclerotic activity, anti-diabetic activity, and cerebral protective effect, among others [58]. Therefore, the intake of A. viridis leaves could provide these healthy properties, if such compounds were bioavailable.

4.6. Antiproliferative Activity of A. viridis Extracts against HT-29 Cells

The extracts of this plant have barely been tested in vitro against cancer cell lines. The antiproliferative effect of the flavonoid extract of the leaves of A. viridis was checked against the MCF-7 breast adenocarcinoma cell line and GI₅₀ was below 30 µg mL⁻¹. Studies attributed this high value to the presence of quercetin [59]. The methanolic extract of A. viridis leaves was tested against the B16F10 melanoma cell line, and it was found that cell viability decreased by 73.59% when 50 μg mL⁻¹ was applied [60], and this extract was also checked against breast cancer MCF7 and MDA-MB-231 cells by House et al. [53], who reported GI₅₀ values of 72.34 and 101.50 µg mL⁻¹.

To check antiproliferative activities against HT-29 cells, the extracts from plants with the highest antioxidant activity, that is, the three wild types, one from EC experiments and another from lighting experiments, were selected. After 48 and 72 h of cultures exposure to hydromethanol leaf extracts, the MTT assay showed concentration- and time-dependent inhibitory effects on HT-29 cells for all checked extracts (Figure 4A,B). The doses of extracts that inhibited the cell growth by 50% (GI₅₀), and those of some pure phenolic compounds after 48 and 72 h of cell cultures exposure to extracts are shown in Figure 4C. Different responses were noted in cells depending on the nature extracts, i.e., wild plants (WT and WU) and GCE ones (CT3 and LT3) induced different cell growth inhibition: HT-29 cells were less influenced by extracts from leaves of GCE plants, which showed higher GI₅₀ compared to wild-type plants (WT: 360 µg mL⁻¹ and WU: 400 µg mL⁻¹). Probably, this situation was a consequence of the high percentages of trans-p-coumaric acid, isorhamnetin-3-O-glucoside, and nicotiflorin in the phenolic extracts of wild plants, all of which exercise anticancer activities, especially trans-p-coumaric acid [56,61].

Furthermore, within GCE plants, there was a differential activity against HT-29 cells between extracts from saline (CT3) and light (LT3) plants: GI₅₀ of CT3 and LT3 were 950 and 850 µg mL⁻¹, although the differential phenolic composition of both plant types is marginal. On the other hand, pure phenolic compounds such as caffeic acid and ferulic acid display varying levels of antitumoral activity compared to plant extracts (Figure 4C). Doxorubicin was used as a positive control, showing a much lower GI₅₀ (3 µg mL⁻¹) than phenolic compounds and plant extracts.

It is necessary to consider that other bioactive compounds that could have been extracted along with the phenolics from A. viridis leaves might have contributed to the quantified antiproliferative activity. For instance, betalains have been reported in A. viridis at ~530 µg kg⁻¹ fw [10], and these pigments develop anticancer actions [62].

Considering all previous information, HT-29 cells have low sensitivity to phenolic-containing extracts, as previously reported [20]. Furthermore, the SI values of HT-29 vs. CCD-18 normal cells were evaluated for plant extracts having GI₅₀ < 400. Extracts with SI > 2 are selective against cancer cells, and when SI < 2, they induce toxicity to normal cells [63]. SI value is decisive when deciding possible future research on any plant material [64]. SI at 72 h ranged from 2.5 (WT) to 3.1 (WU); thus, the extracts from A. viridis were selective against HT-29 cells. Future research focused on the isolation of the various phenolics from A. viridis and the evaluation of their antitumor properties will be welcomed, given that hydromethanolic extracts contain phenols and other polar compounds, e.g, betalains, that could have influenced the noted bioactivity against HT-29 cells.

4.7. Correlations

Figure 5 shows the correlation between the analysed parameters in A. viridis. As expected, both antioxidant methodologies, ABTS and DDPH, showed a high and positive correlation. TPC and TFC showed a positive correlation with DPPH and ABTS, thus contributing to the measured antioxidant activity, although values lack statistical significance. Another positive correlation was found between EC and protocatechuic acid, which may play a role in the tolerant mechanism against salinity stress, similar to that reported in rice [65]. The positive and strong correlations among prominent phenolics are as expected, i.e., when the phenolic biosynthesis is enhanced, all phenolics improve concentrations simultaneously.

The correlations determined for antioxidant activity and phenolic compounds identified that the compounds with the highest correlation with ABTS and DPPH values correspond to protocatechuic acid, trans-p-coumaric acid, nicotiflorin, and isorhamnetin-3-O-glucoside. These phenolic compounds possess chemical structures rich in hydroxyl groups on their aromatic rings, enabling them to effectively donate hydrogen to neutralize free radicals such as those measured by ABTS and DPPH assays. The high correlations observed suggest that these compounds are particularly efficient in scavenging the specific radicals used in these assays, which indicates their potent antioxidant capabilities.

5. Conclusions

Controlling and measuring water absorption in different crop conditions can provide an early indication of the best final yield, and this was the most outstanding indicator among all the fertigation parameters applied in soilless cultures. The EC was around 2.5 dS m⁻¹, while EC of 1.5 dS m⁻¹ or above 2.5 dS m⁻¹ leads to decreased biomass production. The AP67 Milk LED lamp had the best light spectrum to increase the biomass of A. viridis. Interestingly, GCE plants had significantly higher amounts of vitamin C than the wild ones, perhaps due to the absence of stress factors during their development. Notably, the wild samples showed higher antioxidant activity than GCE ones, likely as a defensive response to oxidative stress induced in the wild. In wild plants, trans-p-coumaric acid, isorhamnetin-3-O-glucoside, and nicotiflorin accounted for more than half of total quantified phenolics, while GCE plants showed lower phenolic amounts. The MTT assay showed that wild plants induced higher antiproliferative activity on HT-29 colon cancer cells than GCE ones, possibly due to the occurrence of quercetin glycosides. Noticeable findings are that wild A. viridis contained valuable amounts of phenolics, offering both antioxidant and anticarcinogenic benefits, while GCE plants are richer in vitamin C than wild ones. Further investigations checking the influence of various cultivation conditions on the phenolic profiles and biological activities of A. viridis would outline the results of this work. Additionally, comprehensive in vivo studies are needed to validate the anticancer efficacy of A. viridis extracts across different cancer types, thus properly profiling its potential therapeutic applications.