Fenugreek Galactomannan and Its Versatile Applications

Abstract

Fenugreek (Trigonella foenum-graecum L.) is an annual, dicotyledonous medicinal plant which belongs to the Leguminosae family, and its leaves and seeds are widely used and cultivated throughout the world. Their widespread utilization is attributed to the great variety of primary and secondary metabolites they contain, such as flavonoids, alkaloids, steroidal saponins, tannins, as well as carbohydrates, in particular galactomannan, which is the focus of the current study. The presence of an equal number of galactose and mannose residues (Gal/Man ratio of 1:1) prevents the formation of hydrogen bonds between the mannose ones. This determines the good solubility of fenugreek galactomannan in cold water, even at low concentrations. The water solubility would be significantly better than that of carob and even slightly higher than that of guar gum, precisely due to their structural characteristics, which contribute to their possible advantages. Moreover, it is a good alternative as an excipient for the development of pharmaceutical dosage forms, as well as in the preparation of food products, affecting not only their structure but also their shelf life. Furthermore, it has promising applications not only in the fields of medicine and pharmaceutics but also offers environmental benefits. All of the above-mentioned factors are of high interest and qualify fenugreek galactomannan as a versatile polysaccharide, which is the reason for summarizing its benefits in this review.

1. Introduction

Fenugreek (Trigonella foenum-graecum L.) is a dicotyledonous annual medicinal plant belonging to the Fabaceae family. It is indigenous to the Mediterranean, Egypt, India, North Africa, South and Central Asia, and Southern Europe as well. Nowadays, fenugreek is widely cultivated all over the world. Its species name means “Greek hay”, but it is known by different names in different languages, such as “Methi” in Hindi, “Methika” in Ayurveda, “Alholva” in Spanish, and “K’u-Tou” in Schina.

Trigonella foenum-graecum is an aromatic plant with a cylindrical stem that can reach a length of 30 to 60 cm and it produces individual pods that are 10–15 cm long, each containing an average of 18–20 seeds. The seeds are hard, from rectangular to oval-shaped or rhomboid outline, with a brown, golden brown, or golden yellow color. They have a distinct pungent odor and a flavor that is both slightly bitter and sweet. The seeds are commonly used as a spice in culinary dishes and they are a component of the Indian condiment “curry”, as well as typical in the Bulgarian specialty “Sharena sol”. Fenugreek is well known not only as a food and forage crop but also as a remedy [1,2,3,4,5,6,7,8].

Numerous pharmacological effects and diverse applications related to veterinary medicine, industry, or even assisting environmental management, described in

Table 1. Effects and applications of fenugreek seeds.

No.	Forms (Solvent), Plant Parts	Traditional Uses	References
1.	Dry water extract	Galactologue	[9]
2.	Ethanolic extract	Anti-inflammatory	[10]
		Antineoplastic	[10]
3.	Dry seeds powder	Hypoglycemic	[11]
		Inhibition of β- glucuronidase and mucinase, inhibits colon carcinogenesis	[12]
4.	Seed polder	Biocomposite preparation	[13]
5.	Methanolic extract	Antidiabetic	[14]
	Alkaloid methanolic extract		[15]
6.	Methanolic extracts (a complex mixture of Bifidobacterium breve)	A higher antibacterial effect against H. pylori	[16]
7.	Seed oil	Antimicrobial activity	[17]
		Antifungal activity	[17]
		Develops active starch edible film	[18]
8.	Methanol extract (trigonelline)	Anti-inflammatory effect	[19]
9.	Water extract	Buccoadhesive properties	[20]
		Treatment of mild asthma	[21]
		Anticoagulant/prolonged prothrombin time	[22]
		Protective role against BPA-induced testicular damage	[23]
10.	Hydroalcoholic extract	Controls fleas in pets	[24]
11.	Seed	Increasing testosterone level	[25]
12.	Crude powder	Tilapia culture	[26]
13.	Ethanolic extract	Preparation of conditioning shampoo	[27]
14.	Essential oil	Films for food packaging	[28]
15.	0.3 M NaCl seed extract	Coagulation activity (removal of wastewater turbidity)	[29]
16.	Seed extract	Improves sexual function	[30]

, could be attributed to the variety of bioactive compounds contained in the plant.

The seeds are rich sources of primary metabolites such as water-soluble polysaccharides and lipids. Fenugreek seed oil is a significant source of unsaturated fatty acids, including linoleic acid, palmitic acid, linolenic acid, and oleic acid as well. Their amounts are influenced by various factors such as the stages of seed maturity [31].

In addition to the seed composition, a number of secondary metabolites, including flavonoids, steroidal saponins, tannins, and alkaloids, have been identified.

They consist of pyridine alkaloids such as trigonelline, gentiamine, neurin, and capraine [32,33]. The choline content is beneficial not only for brain processes but also for a number of other physiological functions [34]. One of their positive effects is the increase shown in laboratory rats in their endurance capacity during forced exercise. Trigonelline and 4-hydroxyisolecuine in the extract administered to the mice improved glycogen synthesis and influenced glucose uptake in the muscles and, furthermore, improved dopaminergic transmission [35]. Their identity and purity in plant extracts or herbal medicinal forms could be rapidly and easily established by the chromatographic methods developed [36,37,38].

Previous studies have shown a high content of steroidal saponins in the seeds, both as aglycones named sapogenins and those glycosidically linked. Significant hypolipidemic and blood sugar-lowering effects of dioscin or diosgenin have been described. From seeds rich in yamogenin, tigogenin, sarsasapogenin, and a number of other steroidal saponins, new agents are continuously being extracted and purified due to the numerous and significant utilizations they possess, such as neuroprotective effects [7,39].

Moreover, not only fenugreek seeds and leaves are widely used in various fields, but also fenugreek microgreens could be used as a dietary supplement and they are of significant interest due to their abundant chemical composition and potential antioxidant and antibacterial properties [32,40]. Furthermore, in some countries, germinated seeds containing amino acids and proteins are used to treat Escherichia coli infections [41].

The most abundant primary metabolites contained in fenugreek seeds are polysaccharides and, in particular, galactomannan, the amount of which is estimated at 25–45% of the dry weight of the seeds [42]. Due to its stabilizing, thickening, and emulsifying properties, it has not only applications in the medical and pharmaceutical fields but also in the nutraceutical industry. It is included in the formulation of various milk and meat products, soups, baked goods, and an assortment of powdered or gel-formed products. These versatile applications in a variety of fields are attributed to the specific physicochemical characteristics of fenugreek galactomannan [34].

Numerous studies have focused on the characteristics of fenugreek polysaccharides and their potential applications. However, a comprehensive review integrating all known uses of fenugreek galactomannan is still missing in the literature data. The aim of the current work is to highlight the utilization of fenugreek galactomannan in medicine, pharmaceuticals, engineering, the food industry, textiles, and environmental protection. By encompassing all of these aspects, the present review offers a diverse and complete understanding of fenugreek galactomannan’s perspectives. It emphasizes the versatility and wide-ranging advantages of this polysaccharide, providing insights that can drive innovation and cross-disciplinary applications. Moreover, this approach is settling fenugreek galactomannan as a multifaceted ingredient with significant potential across numerous sectors.

2. Fenugreek Polysaccharide Characteristics

Fenugreek galactomannan consists of linear β-mannopyranosyl residues with (1→4) linkages to which are attached single α-D-galactopyranosyl groups at the O-6 position of the D-mannopyranosyl backbone, where the galactose/mannose ratio is 1:1, or 1:2 in a small number of cases [43,44,45]. The presence of a similar number of galactose and mannose residues prevents the formation of hydrogen bonds between the mannose ones, and this determines the good solubility of fenugreek galactomannan in cold water, even at low concentrations. Consequently, its water solubility would be significantly better than that of carob and even slightly higher than that of guar gum, precisely due to their structural characteristics (Figure 1).

In addition, SEC-MALLS analysis shows molecular weight of 2.235 × 10⁶ g/mol, which is also significant for its nature [45,46,47]. Galactomannan powder is almost pigmentless or has a subtle creamy hue and a slight specific odor reminiscent of fenugreek [8].

The potential applications of fenugreek galactomannan and the exhibited biological activities are presented in (Figure 2) and (Figure 3), respectively.

3. Wound-Healing Activity

Injuries of the skin are a fairly common problem accompanied by inflammation, homeostasis, and proliferation. Despite the widespread use of conventional wound dressings, alternative high-efficacy dressings are increasingly being sought. Additionally, they must not only have the characteristics of classical dressings but also provide rapid healing, be stable and nontoxic, and have excellent mechanical properties. Almost all these qualities, necessary for the rapid and effortless healing of wounds, are shown by fenugreek seed galactomannan hydrogels. The hemostatic capabilities of the hydrogel were reported by Ktary N. et al. to be a major factor in its potent healing effect. They observed a total closure of the wounds on the skin of shaved rats on the 14th day after hydrogel treatment [48]. Deng et al. combined cellulose and fenugreek galactomannan to prepare a composite hydrogel possessing a fibrous porous structure. They showed the importance of galactomannan in the hydrogel’s performance through its influence on the degree of crosslinking and the number of hydrophilic groups of the hydrogel. Not only the hemostatic efficacy but also the good biocompatibility and low toxicity of the hydrogel have been demonstrated. Altogether, it may be an effective treatment alternative for wounds [49].

4. Cholesterol-Lowering Agent

Galactomannan isolated from Trigonella foenum-graecum L. is well known for its cholesterol-lowering properties. As early as the 1990s, Evans et al. emphasized the significance of the galactose/mannose ratio (1:1) in its composition in reducing liver and plasma cholesterol levels. Male rats were subjected to a diet including 80 g/kg galactomannan from fenugreek, gum guar, and locust bean. The high density of the galactose side chain in the fenugreek galactomannan resulted in the most significant cholesterol-lowering effect [50].

Boban et al. demonstrated a remarkable decrease in total cholesterol in the serum of rats after treatment with different types of stickiness, one of them being galactomannan from Trigonella foenum-graecum. The solution was given immediately before feeding, and the results showed not only a reduction in the level of total cholesterol when galactomannan was introduced into the diet of the rats but also of triacylglycerols [51].

5. Hepatoprotective Activity

Globally, diabetes mellitus is one of the most significant chronic diseases, with over 400 million people currently affected, and this number is expected to reach 600 million by 2040. Because of the widespread prevalence of the disease and its numerous complications, such as liver damage, new natural hepatoprotective alternatives are continuously being explored. They should be both effective and affordable while keeping adverse effects to a minimum [52].

In this regard, Alsuliam et al. confirm data from previous studies showing the hepatoprotective properties of fenugreek galactomannan. It exhibited positive results in its administration to streptozotocin type 1 diabetes mellitus rats. Additionally, galactomannan improves pancreatic β-cell structure, reduces oxidative stress, and inhibits inflammation, demonstrating greater potency than fenugreek aqueous extract. Its administration reduced elevated liver functional enzymes ALT and AST in diabetic rats and normalized serum albumin, urea, and creatinine levels.

Feki et el. demonstrated a reduction in the plasma levels of markers of hepatotoxicity such as alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase by administration of fenugreek polysaccharide against thiamethoxicam-induced hepatotoxicity in female rats [53].

6. Antidiabetic Activity

Enhancing glucose uptake by peripheral cells and tissues is an effective method to reduce blood glucose levels. Rat hemidiaphragms treated with fenugreek galactomannan exhibited a significant increase in glucose uptake compared to untreated samples, although this was lower than the increase induced by a standard antidiabetic drug.

Chronic hyperglycemia in both diabetic and experimental animal models leads to elevated oxidative stress and reduced activity of antioxidant enzymes like catalase, superoxide dismutase, and glutathione peroxidase. Diabetic rats treated with fenugreek galactomannan exhibited a minor reduction in lipid peroxidation and an increase in antioxidant enzyme levels. Although galactomannan does not exhibit a greater antioxidant activity relative to a standard antidiabetic drug (glibenclamide), it is significantly higher compared to the untreated diabetic rat group [11].

Srichamroen et al. demonstrated a dose-dependent decrease in glucose uptake from the jejunum and ileal segment of the intestine at either low (2 mmol/L) or high concentrations (32 mmol/L) under the influence by galactomannan isolated from fenugreek grown in Canada. It has been suggested that this is attributed to its ability to increase the effective resistance of the aqueous layer and create a “physical barrier” to glucose diffusion [54].

Kambe et al. showed dose-dependent (50, 100, and 200 mg/kg) antihyperglycemic activity of a 91.5% purity low-molecular-weight polysaccharide fraction (LMWGAL-TF) from fenugreek seeds in alloxan-induced hyperglycemia in mice. The LMWGAL-TF inhibited inflammatory cytokines in the diabetic condition and resulted in the prevention of diabetic cachexia [55].

Glycosylated hemoglobin is employed as a biomarker in diabetic patients to assess glycemic control over the last 2 to 3 months. Fenugreek galactomannan significantly reduced its level compared to a control group of diabetics. These results suggest that its administration could contribute to maintaining glucose levels over the long term and prevent possible diabetes complications [11].

An aberrant composition of the intestinal microbiota has been found to be closely related to metabolic diseases, including diabetes mellitus. Fiber facilitates the production of short-chain fatty acids, which stimulate intestinal gluconeogenesis. Shtriker et al. demonstrated lower fasting glucose levels in mice on a fenugreek galactomannan diet [56].

Galactomannan moderates the intestinal flora, increases the movement of the bowels, slows the evacuation of carbohydrates from the stomach, and affects the digestive enzymes. In this manner, it reduces blood glucose levels in diabetic patients [30].

7. Prebiotic Applications

The significant influence of prebiotics, such as polysaccharides, on the human body and its health condition is widely known. They lead to the production of important short-chain fatty acids, such as butyrate, propionate, and acetate. Moreover, they might have not only a positive effect on bone density and on better calcium absorption, but they also have a major role in the immune system [57,58]. To be used as a prebiotic, galactomannan needs to correspond to a number of conditions, one of which is to be resistant to gastric acid to remain unchanged for the colon microbiota. After three hours of exposure to the pH of gastric acid, fenugreek galactomannan relatively retains its structure and nondigestibility by pancreatic enzymes. In addition, Majeed et al. reported its fermentation by Bacillus coagulans MTCC 5856 and the production of short-chain fatty acids as a result. Despite the need for further investigations, there is evidence to believe that fenugreek galactomannan exhibits good potential prebiotic properties and may contribute to the development of symbiotic products [59]. Supporting these claims is its demonstrated persistence against pepsin and pancreatin in the growing rabbit’s stomach; however, it is influenced by the bacteria in their caecum [60].

8. Breast Cancer

Cancer is one of the most significant global health problems. The International Agency for Research on Cancer (IARC), for instance, rated both breast and lung cancers as the most common cancers in 2022. Breast cancer incidence is 11.6%, which makes it the cancer with the second highest incidence. Concerning women, it is the most frequently diagnosed cancer, with 666,000 deaths recorded in 2022 alone, which is about 6.9% of all cancer deaths. These considerable numbers lead scientists to continuously explore new developments in cancer prevention and treatment [61]. Fenugreek is well known to have anticancer properties and the ability to induce apoptosis. With molecular docking, a method that gives us information about atomic-level interactions, and molecular dynamics simulations, it is revealed that fenugreek galactomannan possesses activity against both type 2 diabetes and breast cancer. Furthermore, the galactomannan–curcumin complex shows a propensity to modulate multiple protein/signaling pathways that are key in a number of chronic inflammatory diseases such as cancer. Despite the need for multiple further studies, fenugreek galactomannan is a potential agent to fight carcinogenic diseases in the long term [62,63].

9. Anti-Obesity Capabilities

Obesity is one of the prevalent global health problems throughout the world. Therefore, scientists are constantly studying various aspects of it and strategies to manage its effects. It has been suggested that the high fiber content of fenugreek seeds is a major reason for its effect on obesity. They may exhibit their gelling properties and reduce food absorption. In addition, by increasing their volume in the stomach, they can induce a feeling of satiety and reduce appetite [64]. Jang et al. reported that adding 8 g of fenugreek fiber to breakfast led to a greater feeling of satiety, although the fiber did not affect energy intake during the rest of the day [65].

10. Antioxidant Capabilities

Ktari et al. demonstrated, determined by thiobarbituric acid-reactive substances (TBARS), the antioxidant activity of fenugreek galactomannan beef sausage. They showed not only a good inhibition of the lipid peroxidation of meat products during storage but also that galactomannan’s ability to neutralize free radicals surpassed even that of vitamin C [66]. Increasing evidence shows the antioxidant properties of fenugreek polysaccharides, making them a promising source for both nutritional and medicinal applications. Moreover, in vitro studies have validated their efficacy in reducing hematological, hepatic, and histological damage induced by pesticides like Thiamethoxam. Despite the benefits of pesticides, proven during World War II through their application in reducing the spread of infectious insect diseases and undeniably increasing agricultural yields, the risk they pose to human health is significant.

They can have adverse effects not only on the reproductive systems of both men and women, but studies have even established a link between pesticide exposure and cancer. For that reason, new ways of reducing the harmful effects of pesticides on human health are constantly being sought. Polysaccharides, such as galactomannan, would be an affordable, efficient, and effective way to solve this worldwide problem [53,67].

11. Mucoadhesive Properties

Beads of fenugreek seed mucilage–gellan gum (FSM-GG) blends containing metformin HCL were evaluated not only for their drug release properties but also for their mucoadhesive properties. Nayak et al., 2014, carried out wash-off tests using goat intestinal mucosa, and the results confirm the mucoadhesive abilities of the FSM-GG beads in the gastrointestinal tract. This could enhance the bioavailability of the dosage form due to prolonged gastric retention time and good contact with the absorptive mucosal membrane. In turn, it could also reduce the necessity for re-administering the dosage form due to drug release over extended periods [68].

Confirming the good mucoadhesive properties of fenugreek polysaccharides are the trials reported by Ratha et al., 2017, on buccal patches containing an anti-hypertensive drug combined with fenugreek seed galactomannan with hydroxylpropyl methylcellulose. They observed that atenolol-delivering buccal patches increased their mycoadhesiveness when fenugreek galactomannan was part of the formulation [69].

12. Colon Tablets

Researchers are constantly looking for new alternatives to optimize drug dosage forms to increase their effectiveness and to reduce the adverse effects of conventional ones.

Therefore, they are turning to the use of plant polysaccharides as excipients due to their advantages. Colon tablets based on fenugreek galactomannan are a promising option against Entamoeba histolytica. They have demonstrated effective drug release of metronidazole in the colon, where trophozoites reside. The Gamma Scintigraphy Study showed that the polysaccharide contained in the metronidazole colon tablet avoids the rapid release of medication in the upper part of the gastrointestinal tract (GIT) and minimized it in the other part of the GIT. In the presence of fenugreek galactomannan, metronidazole remains stable and unchanged until the colon, where it is needed to be effective [70].

To protect tamoxifen-containing tablets from rapid release in the other part of the GIT until their transfer to the colon, Rhandala et al. used an interpolymer complex of charboximethyl fenugreek gum and chitosan (CMF-CH) in a 40:60 ratio. They established significant release of tamoxifen in the rat intestine, which could also be due to anaerobic enzymes that target polysaccharides specifically therein [71].

13. Coagulants and Flocculants

The increasing water needs of society lead to a continuous search for new, cheap, effective, and at the same time safe methods for water purification. One of these methods is coagulation and flocculation by bioflocculants like biopolymers from plants, animals, algae, etc. They offer numerous benefits, such as nontoxicity and biodegradability. The ability of fenugreek seeds to act as coagulants and flocculants is attributed to the presence of polysaccharides in their composition. Kim et al. showed the efficacy of the combination of fenugreek seeds and Hibiscus esculentusas (okra) fruit in the industrial treatment of palm oil mills. They established optimal conditions for a substitute for chemical flocculants and coagulants, namely 4.6 g/L of fenugreek and okra in a concentration of 40 mL/500 mL palm oil mill effluent.

Venegas-Garcia and Wilson determined the optimal coagulant dosage for arsenic removal to be 52 mg L⁻¹, 62 mg L⁻¹ with a Box–Behnken statistical experimental design. Fenugreek gum’s efficiency, low cost, and biocompatibility make it an appropriate option for wastewater treatment [29,72,73]. Due to its aforementioned characteristics, it can be used to synthesize a gum-based hydrogel to remove industrial contaminants such as malachite green [74].

14. Food Packaging

One of the most significant challenges affecting ecosystems worldwide is the problem of plastic pollution, largely due to hundreds of millions of tons of single-use plastic packaging. With rising living standards and the consumption of individually packaged food and beverages, this is increasingly a challenge [75]. Plastic pollution not only causes enormous financial damage, amounting to some EUR 21 billion worldwide, but there is also mounting talk of increased risks to human health from the inhalation, ingestion, or dermal route of microplastics and nanoplastics. According to the literature, one of the main sources through which they enter the human body is drinking water. It has been estimated that billions of microplastic particles can enter the environment daily from the consumption of tea bags and bottled water alone. Despite the need for more research and evidence, the close association between exposure to micro- and nanoplastics and the development of tumor processes in the human body is increasingly commented upon [76].

Not only beverages but also single-use food packaging is a major reason for global plastic pollution. Therefore, a number of methods and approaches are being sought worldwide to tackle this global problem [75].

Hence, there is a constant search for food packaging alternatives that are affordable, renewable, biodegradable, and nontoxic and simultaneously preserve and protect food from the effects of the external environment by maintaining its fresh condition and qualities for a while longer. Polysaccharides are primary metabolites satisfying all these requirements. Lindi et al. demonstrated good results testing apples coated with edible films of fenugreek polysaccharide compounds and rosemary essential oil compared to uncoated ones. Despite the need for further work on evaluating the antimicrobial activity of galactomannan-based films, the results indicate that essential-oil-loaded polysaccharide films extend the shelf life of apples. However, such edible films based on fenugreek polysaccharides would be a good alternative for coating a number of foods. This can lead to positive results in the difficult plastic pollution control fight [77].

In addition, the use of edible film coatings containing fenugreek and flaxseed polysaccharides showed maintenance of apple quality during storage. The film coating on the surface of the fruit helps to decrease the weight loss through its low permeability to water vapor and the barrier that is created between the apple and the surrounding environment [78].

This evidence suggests that fenugreek galactomannan would be a good alternative to single-use food packaging, reducing plastic pollution and helping deal with this significant environmental problem worldwide.

15. Textile Printing Agent

With the development of the economy, the textile industry is increasingly growing. This leads to an accelerating demand for more and more colorful and patterned products. Subsequently, this increases the use of synthetic dyes and thickeners, which can lead to harmful effects. Therefore, there is a continuous effort to find natural substitutes that are not harmful to humans or the environment but are also affordable and cost-effective. These conditions are largely addressed by fenugreek galactomannan. Although it has a lower viscosity compared to guar gum, for instance, following oxidation under microwave irradiation, the authors report its possibility to be used for reactive printing on cotton [47,79].

16. Tissue Engineering

Polysaccharides are biocompatible, biodegradable, nontoxic, easily degradable, and easily provided because they are abundant in various plant materials (leguminous). Their porous structure and large surface area, as well as the presence of polyhydroxyl groups, determining their numerous physicochemical and mechanical properties, make them especially favorable for constructing scaffolds in tissue engineering [80,81].

Bone tissue, for instance, which is highly vascularized, has the ability to continuously regenerate, thereby maintaining its structural integrity. However, remodeling is only possible for small bone deformations, while for larger ones it is necessary to use bone substitutes (grafts or allografts), which may always be rejected. For this reason, tissue engineering is constantly looking for new methods such as the use of biopolymers such as polysaccharides aimed at providing a scaffold for tissue repair and reconstruction. Zia et al. developed a bioactive nanocomposite consisting of nano-hydroxyapatite, chitosan, and fenugreek galactomannan. In vitro studies revealed not only excellent cytocompatibility and hemocompatibility but also a good ability to absorb both moisture and protein, which are attributed to Trigonella-foenum graecum polysaccharide [82,83].

17. Food Applications

Moreover, the addition of fenugreek paste to chicken meat sausage may improve its texture. The galactomannan contained in the paste, due to its specific chemical structure and properties, increases water absorption, which makes the sausage more tender and softer. Patriani et al. showed that the addition of 4% fenugreek paste significantly improved the texture of the tested sausages and reduced their weight loss during food processing. Furthermore, the addition of the paste also affected the color of the meat product, which may further increase its purchasability [84].

Hydroxyl group-rich fenugreek galactomannan has the ability to hold water and modify its viscosity. Therefore, its inclusion in baked products such as muffins would not only increase their fiber content and improve their nutritive value, but its reuse would also reduce pollution from its release to the surrounding environment [85]. The combination with fenugreek galactomannan not only improves the rheological properties and taste characteristics of muffins but can also be used as a fat substitute and as a good source of dietary fiber.

18. Moisturizing Ability

It is a known fact that, due to the large number of hydroxyl groups contained in the structure of fenugreek galactomannan, it possesses the notable ability to retain water molecules. Therefore, its use is increasingly widespread, not only in the pharmaceutical and nutraceutical industries but also in a variety of fields.

Water scarcity and drought are a serious problem that humanity is continuously struggling with at different levels. For example, agriculture is constantly looking for methods to enhance water retention in the soil, which maintains water balance and benefits plant development. In this regard, Lui et al. included galactomannan in the composition of borax-crosslinked hydrogel and established a good binding of borate ions to the hydroxyl groups of galactomannan. The borate ion and two diol units of the mannose chains bind to afford borate/diol complexation by the crosslinking mechanism. This results in a hydrogel possessing significant self-healing properties. FTIR analysis showed that the scaffolding and linkages between the sugar residues of fenugreek were still stable. The authors assessed the swelling index of the gel to establish its absorption capacity. It was observed that an increase in the galactomannan concentration above 0.5% led to a reduction in the swelling degree. The incomplete crosslinking reaction with borax may be the reason affecting its water-binding properties. Hydrogel containing fenugreek galactomannan with a mannose/galactose ratio of 1:1 demonstrated a higher swelling index compared to guar gum, which had a mannose/galactose ratio of 2:1. Furthermore, the highest swelling index was observed in an aqueous solution with alkaline pH. This was probably due to the increase in hydrogen bonds and the expansion of crosslinked chains.

The investigated hydrogel showed both an increase in the sandy soil swelling index and also an improvement in water retention time. Moreover, it exhibited higher swelling index results compared to commercial products such as guar gum. In addition, the hydrogel test demonstrated improvements in both soil porosity and wind protection. This would suggest to us that its potential application in agriculture could bring benefits both economically and environmentally [86,87].

Wang et al. demonstrated the remarkable moisturizing properties of a low-molecular-weight polysaccharide fraction of fenugreek seeds included in a cigarette formulation. Molecular weight, cationic charge, and hydrophobicity are the main factors affecting the moisturizing activity of polysaccharides. They not only contribute to the tobacco’s rheological properties and flavor but also do not lead to the breakdown of noxious degradants while smoking compared to other moisturizing agents. This is a significant aspect in the selection of excipients in the tobacco-processing industry [88].

19. Battery Binders

Nowadays, the use of batteries, both lithium-ion and other types, is increasingly widespread in daily routines, even for electric transport. Despite the technologies developed to produce them, new methods and techniques are constantly being explored to increase their energy density and capacity over a longer period of time. Binding agents, such as galactomannans, play an essential role in this context. Qiu et al. reveal that the binding agent carboxymethyl fenugreek gum can be applied to silicon anodes. Its primary function is to increase the adhesion between the current acceptor and the active material and thus enhance its electrochemical performance. Enhancing the carboxymethyl groups in the carboxymethyl fenugreek gum (CFG) leads to stronger hydrogen bonds between the silica particles and the CFG binder. Consequently, the specific capacitance is higher, and the electrodes bonded to the CFG maintain high capacitance even after 200 charge and discharge cycles. Comparisons with the conventional carboxymethyl cellulose (CMC) binder and a polymeric guar gum binder demonstrated the crucial role of fenugreek polysaccharide chemical composition in the CFG complex structure. The results showed that the Si anode with CFG-2 had a higher specific capacitance than those with CMC and guar gum [89].

Even after 200 charge/discharge cycles, carboxymethyl fenugreek gum could maintain the battery capacity over 1500 mAh/g. Modified galactomannan isolated from fenugreek seed endosperm is affordable, renewable, nontoxic, and biodegradable. This makes it a promising binder in the battery industry [89,90,91].

20. Conclusions

Galactomannans, widely distributed in plant species, are finding future perspectives in a number of fields. One of the most common is fenugreek galactomannan, which consists of a specific structural backbone of β-mannopyranosyl residues with (1→4) linkages and attached single α-D-galactopyranosyl groups at the O-6 position, where the galactose/mannose ratio is 1:1. This determines the good solubility of fenugreek galactomannan in water, even at low concentrations. These properties establish it not only as a very good tableting auxiliary but also as a moisturizing agent; therefore, it finds applications in both the food and textile industries. Its pharmacological and therapeutic effects, including lowering cholesterol and blood glucose levels, as well as wound healing activity, are well established. Nowadays, fenugreek galactomannan is considered a potential carcinogenic-disease-fighting agent in the long term and a tissue-engineering polymer.

Despite considerable attention being paid to guar gum and locust bean gum, recent focus is increasingly shifting to fenugreek gum as well [47,92]. Compared to them, it exhibits a greater surface charge and better gelling ability, making it a more advantageous alternative for diverse applications [93]. The current review demonstrated that fenugreek galactomannan, due to its unique chemical properties, has good potential as a moisturizing agent not only in the pharmacy and food industries but also in the agriculture field. Moreover, it could be used in medicine owing to its numerous therapeutic effects. Galactomannan isolated from fenugreek seeds is renewable, bioavailable, biodegradable, affordable, and nontoxic, and, therefore, it is a promising bioactive agent for a variety of applications.