**3. Biological activities**

#### **3.1 Antioxidant activities**

Natural products, such as mushrooms, vegetables, cereal, flowers, and wild fruits, have been extensively studied for their antioxidant properties. Antioxidant bioactive compounds have the ability to slow the oxidation process of important biomolecules found in human tissues and cells. It has been known that overproduction of free radicals plays a significant role in the onset of many chronic diseases such as Alzheimer's disease, various types of cancer, and diabetes. As can be seen from a review of some literature, the production of bioactive compounds is often less than 1% of the dry weight of the legume. Therefore, based on this consideration, even a technique such as chemical synthesis cannot yield large quantities of bioactive compounds.

Antioxidant activities of various legume species have been identified in numerous studies, with a positive association between antioxidant activities and total phenolic content. The chemical composition of phenolic compounds impacts their antioxidant function. The position and degree of hydroxylation on the B ring are the most significant factors in the activity of flavonoids, which are considered primary antioxidants [51]. Natural precursors of flavones and flavonols are chalcones, which have antioxidant potential (**Figure 9**) [25]. Several methods have been developed and utilized to evaluate the antioxidant activities in legumes, including *in vitro* assays for ferric-reducing antioxidant potential assay (FRAP),

**Figure 9.** *Chemical structure of chalcone.*

#### *Nutraceutical Properties of Legume Seeds: Phytochemical Compounds DOI: http://dx.doi.org/10.5772/intechopen.100171*

Trolox-equivalent antioxidant capacity (TEAC), 1-diphenyl-2-picrylhydrazyl free radical-scavenging assay (DPPH), the tests to measure values of oxygen radical absorbance capacity (ORAC), and total radical-trapping antioxidant parameter (TRAP). Xu and colleagues showed that dark-colored pulses had higher phenolic content and antioxidant activity than pale-colored pulses [19]; the same was true for anthocyanins, which attracted interest for their high antioxidant effects. Their study also reported that lentils had the highest DPPH and ORAC activity than green pea, yellow pea, and chickpea [52]. Similarly, lentils were observed to have the highest total antioxidant potential measured by FRAP and TRAP, among test pulses, but came in the second place by TEAC to broad beans [8], because seed coats contained mainly flavonoids, hydroxycinnamic, and hydroxybenzoic acids [25]. Red, brown, and black beans have been reported to have strong antioxidant activities in comparison with white beans [3]. More importantly, the antioxidant activity of the common bean seed coat was found to be higher than that of the cotyledon in several studies [20]. M. Dueñ et al. [25] demonstrated that the seed coats of lentils (with EC50 values were between 0.05 and 0.07 mg of sample) had a higher free radical-scavenging capacity than in cotyledon (with values from 21 to 29 mg of sample). Another research found that red kidney beans had the most antioxidant activity (15-μmol Trolox equivalents (TE)/g seed dry weight), while brown-eyed bean varieties had the least (6.22-μmol TE/g seed dry weight) [3].

In different circumstances, processes such as thermal processing, fermentation, and germination have a major impact on the antioxidant activities of common beans. Because of the increased level of total phenolic content, germination and fermentation may enhance the antioxidant properties of legume seeds even further. In some studies, it was noticeable that the antioxidant activities significantly increased in peas 4 days after germination and in the presence of light [27].

## **3.2 Antibacterial activities**

Antimicrobial resistance has made the spread of bacterial, fungal, and viral infectious diseases a major public health concern. Natural compounds from plants are nowadays excellent candidates for use as alternative sources of antimicrobial substitutes. Legume seeds, which are high in phytochemical varieties, used these chemicals to defend themselves against microbes, pathogens, etc. The aforementioned antinutritional compounds, protease inhibitors, and polyphenols have been shown to be highly biologically antimicrobial agents [40]. Besides antioxidant agents, phenolics are also demonstrated in antibacterial potential against a wide spectrum of microorganisms. Polyphenols deplete critical essential mineral micronutrients (iron and zinc), disrupt the cytoplasmic membrane, inhibit microbial metabolism, and cause permeabilization of the cell membrane, resulting in microbe death [40]. Flavol-3-ols, flavonoids, and tannins (**Figure 10**) have received the most attention, because of their efficiency in resisting a variety of microbial virulence factors such as inhibition of biofilm formation, ligand adhesion reduction, and bacterial toxin neutralization [53]. Moreover, prenylated phenolics derived from legume seedlings indicated potent antibacterial activity against *Listeria monocytogenes* and methicillin-resistant *Staphylococcus aureus*; this compound has also served multiple goals, including providing health benefits and natural food preservation [54]. Protease inhibitors are also thought to have antimicrobial properties, and their mechanisms of action involve suppressing enzyme activities in response to attack by phytopathogenic microorganism-produced proteases. Methyl esterification of protein by methanol, which is isolated from broad bean, chickpea, and soybean, revealed efficient antibacterial activity against *Escherichia coli, S. aureus, Bacillus subtilis,* and *Pseudomonas aeruginosa* [40]. Methylate subunits interact with cell

**Figure 10.** *Chemical structure of tannin.*

walls and cell membrane, produce channels and pores and affect the integrity of bacteria cells, and finally achieve the lysis and death of the microorganism [55]. Antimicrobial peptides (AMPs) from natural sources of plants are generally effective against a wide range of microorganisms by interaction or disruption of the bacterial cell wall. Lectins are carbohydrate-binding proteins involved in plant's defense through the growth inhibition of bacteria, or disruption of the microbial cell wall by interacting with components on them such as teichoic and teichuronic acids, peptidoglycans, and lipopolysaccharides [53]. The seed extracts of lentils, fava beans, and peas show antibacterial activity (*P. aeruginosa* and *S. aureus*) [56]. AMPs derived from chickpeas, such as cicerin and arietin, have shown antifungal activity against *Botrytis cinerea, Mycosphaerella arachidicola, and Fusarium oxysporum*; and serine proteinase inhibitors that are found in chickpea seed extracts display antimetabolic activity against *Helicoverpa armigera* [40]. The effect of water extracts of colored azuki beans (such as green, black, and red) has been revealed to be more effective against *S. aureus, Aeromonas hydrophila,* and *Vibrio parahaemolyticus,* due to higher concentrations of polyphenols including proanthocyanidins, compared with the extracts of white azuki beans, which indicated no inhibition toward any of the bacteria examined [55].

In summary, the antibacterial properties of legumes are related to their variety and processing methods. These effects can be attributed primarily to the suppression of bacterial biofilm formation, cell wall disruption, and inhibition of microbial metabolism.

#### **3.3 Anticancer activities**

Cancer is recognized as the leading cause of death worldwide, and several research works have indicated that plant-derived secondary metabolites possess properties that fight against types of cancer varieties. According to the American Institute for Cancer Research (AICR), legumes contain a variety of compounds that may protect the human body against cancer, including lignans, saponins, resistant starch, and polyphenolic compounds [8]. Phenolic compounds, bioactive protein, and short-chain fatty acids extracted from legume seeds have several bioactive activities related to anticancer potentials, such as anti-inflammation, anti-proliferation, and pro-apoptotic effect [19]. Many studies reported that phenolic and flavonoids that are derived from plants exhibit potent anti-inflammatory activity

*Nutraceutical Properties of Legume Seeds: Phytochemical Compounds DOI: http://dx.doi.org/10.5772/intechopen.100171*

by regulating the concentration of various inflammatory cytokines or mediators such as cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF-α), and nuclear factor-kappa (NF-κB), interleukin 1, interleukin 6, interleukin 10, nitric oxide (NO), lipoxygenase (LOX), and iNOS [8]. Flavonoids isolated from black bean hulls can affect cell cycle by inducing cell cycle arrest at the S-phase and preventing progression to G2/M stages, as well as causing activation of apoptosis on OCI-Ly7 lymphoma cells in mouse [57]. In another experiment, phytosterol treatment reduces the development of production of carcinogens, inhibits cell growth, and also promotes apoptosis in cancer cells [10]. Saponins similar to those present in soybeans have been shown to have anticancer activity. Ginsenosides, a form of saponins isolated from ginseng, have been indicated to inhibit tumor cell proliferation and induce tumor cell differentiation and apoptosis in an *in vitro* assay, as well as *in vivo* to inhibit tumor invasion and metastasis [51]. In fact, several polypeptides have recently been researched and found to have powerful anticancer potential. Anticancer peptides derived from legumes can be found in the form of an intact long polypeptide chain, or they can be synthesized from their protein precursors through enzymatic hydrolysis [18]. Lunasin, a leader anticancer peptide derived from soybeans and other legumes, inhibits the chemical carcinogen-induced transformation of murine fibroblast cells to cancerous foci and induces selective apoptosis (**Figure 11**) [50].

Experimental studies have demonstrated that legume seeds and their active components can prevent and treat several types of cancers. These anticancer mechanisms mainly involve the regulation of carcinogen metabolism, inhibition of cell growth and proliferation, and induction of apoptosis.

#### **3.4 Cardiovascular protection**

Cardiovascular diseases have been considered to be a leading cause of premature death, of about 17.9 million people die per year. Dyslipidemia, hypertension, and type 2 diabetes are known to be risk factors for cardiovascular diseases, including stroke and coronary heart disease. A series of studies has shown that legume seeds can decrease the levels of blood lipids and blood pressure, contributing to protection from cardiovascular protection [11].

Legumes are rich in phytosterols, which have been demonstrated to inhibit the absorption of cholesterol in the intestine, followed by decreasing levels of low-density lipoprotein-cholesterol (LDL-C) and TAG, and enhanced the concentration of serum high-density lipoprotein-cholesterol (HDL-C) in the blood, a protective factor against coronary heart disease (CHD) [40, 58]. Furthermore, β-sterols, which are abundant in chickpeas, help to lower serum cholesterol, blood pressure, and

the risk of coronary heart disease [40]. Chickpeas also are high in dietary fiber, which help to lower total plasma cholesterol levels and can aid in weight loss and obesity reduction. These compounds are also thought to improve body metabolism and reduce chronic inflammation, serum lipid levels, blood pressure, and insulin resistance, as well as to affect fibrinolysis and coagulation, which may be essential in the plaque formation of existing atherosclerotic plaques [59].

Generally, legume has exhibited cardiovascular protective effects by attenuating hypertension and ameliorating dyslipidemia, such as in the improvement of HDL-C, reduction of LDL-C, TAG, and blood pressure.

#### **3.5 Other bioactivities of legume**

Apart from the bioactivities mentioned earlier, legume has other beneficial effects, such as anti-obesity and antidiabetic effects.

Diabetes mellitus is known as a severe metabolic disorder caused by insulin deficiency and/or insulin resistance, resulting in an abnormal increase in blood glucose. Legumes have been shown to regulate the levels of blood glucose and, in turn, provide protection against diabetes by resistant starch (NSPs). Moreover, short-chain fatty acids and the inhibition of α-amylase and α-glucosidase have been reported to induce hypoglycemic and hypocholesterolemic effects by suppressing glucose release and cholesterol production [17, 60]. Adzuki bean extracts reduce the final body weight of mice and adipose tissue accumulation and enhance lipolysis. This treatment also considerably decreases the serum triglyceride levels, total cholesterol, LDL-C, and liver lipids [61].

#### **3.6 Benefits of legume seeds in aquaculture**

Legumes contain large amounts of valuable protein. These proteins are not only abundant but also have a well-balanced amino acid profile, and may be used to substitute fish meal, which is an unsustainable resource. The substitution of plant protein sources for fish meals without compromising fish growth and physiology is a strategy for lowering feed costs and reducing aquafeed reliance on fish meals. Some studies reported that commercial hexane-extracted soybean meal with methionine supplement could replace 67% of the fish meal in the diet without negatively impacting milkfish growth and feed conversion ratio [62]. Another experiment showed that the substitution of up to 20% of fish meal protein with soybean meal protein in realistic diets for spotted rose snapper was an essential move for this high-value species [9]. Green mung bean in which the ANFs were inactivated by thermal processing was used as a replacement for fish meal in Asian sea bass and milkfish diets, with no negative effects on the fish's development [62, 63], and these studies were carried out on a 15-week feeding trial and were evaluated to measure growth, survival, FCR, PER, HSI, and liver and gut histology. Overall, legume is a promising alternative protein source for the aquaculture feed industry.

#### **4. Conclusions**

In conclusion, the utilization of legumes as food ingredients is of tremendous interest, not only for increasing the functionality of food items but also for developing functional foods with health advantages. The content, composition, and distribution of legumes, as well as their biological functions, are systemically outlined and analyzed in this review. However, the following aspects require additional investigation to fill knowledge gaps.

*Nutraceutical Properties of Legume Seeds: Phytochemical Compounds DOI: http://dx.doi.org/10.5772/intechopen.100171*

The extraction solvent has a significant impact on the extraction efficiency of bioactive substances. Mathematical modeling, such as response surface methodology, which is an ideal candidate for predicting the interactions between the target compound and solvent, has been successfully applied in the selection of a specific solvent for higher compound extraction yield in many plants. However, no study has used these modeling tools to optimize the extraction conditions of legume chemicals yet. As a result, future research can use these methods to reduce the time and effort required to identify solvents for common bean polyphenols in different kinds.

Furthermore, the research should seek more bioactive substances and investigate their benefits, as well as biologically active metabolites. Thus, future study can focus on extracting and purifying novel active chemicals from legumes, and clinical trials are also required to confirm the medicinal advantages of legumes. Moreover, legumes have the high potential to be a valuable substitute source of feed for the aquaculture industry.
