**2.4 Anti-hypertension properties**

Hypertension is one of the most important factors (apart from diabetes and high cholesterol level) causing cardiovascular disease in humans which is characterised by the increase in systolic/diastolic arterial pressure [42]. Studies have well documented that healthy diet/lifestyle i.e. reduce sodium intake and physical exercise are important factors controlling blood pressure, hypertension and ultimately risk of cardiovascular disease [42]. Various major and underutilised legumes are rich source of secondary metabolites, fibres and micronutrients thus forming an important framework of plant's bioactive compounds for healthy diet [43]. For example, some bioactive peptides from food as well as grain legumes have demonstrated their potential to combat both hyper and hypotensive effects. Peptides having Glu-Phe, Ile-Arg and Lys-Phe dipeptides identified form legume crops have shown antihypertensive effect by inhibiting the activity of Angiotensin-I- Converting Enzyme (ACE) [36, 44]. Similarly, proteins like tyrosinase and lupin present in legume crops have also shown their remarkable ability control both systolic/diastolic blood pressure in peoples suffering from hypertensive disorder [44].

The hypertensive property of both lupin and tyrosinase have also been extensively investigated under in vivo conditions in Goto-Kakizaki rats suffering from hypertension due to excessive consumption of Na rich diet. The researchers fed the hypertensive rats with both lupin and tyrosinase for two weeks and then observed significant reduction in the systolic/diastolic pressure in both the groups [45]. However, lupin treatment also significantly improved endothelium-dependent vasodilation in hypertensive rats more efficiently as compared to tyrosinase [45]. A large

*Unlocking Pharmacological and Therapeutic Potential of Hyacinth Bean (*Lablab purpureus *L.)… DOI: http://dx.doi.org/10.5772/intechopen.99345*

body of literatures have also indicated that these bioactive peptides/proteins do not only possess hypertensive and ACE inhibitory effect but are also actively involved in lowering cholesterol and lipid levels [44]. Researchers have also extensively studied hypocholesterolaemia by using bioactive peptides and proteins and identified that the peptide Ile-Ala-Val-Pro-Gly-Glu-Val-Ala was compellingly involved in lowering cholesterol and triglycerides levels by stimulating the activity of bile salts [46]. Furthermore, other studies have also well documented the role of soybean peptides/ proteins in efficiently controlling high cholesterol and lipid levels by efficiently modulating ratio of low density/high density lipo-proteins and expression of beta-very-low-density lipoprotein (β-VLDL) receptors thus minimising risk factors for cardiovascular disease [46]. Researchers have identified and evaluated several of these bioactive peptides from other legumes crops as well, however efforts are needed for in-depth characterisation of their function and mode of action in other underutilised legumes such as in hyacinth bean.

#### **2.5 Antioxidative properties**

Reactive oxygen species (ROS) generated as a consequence of oxidative stress are concomitantly involved in the onset and progression of various chronic diseases. Increased level of ROS has been shown to instigate severe damage to nucleic acids, cause membrane damage via lipid peroxidation and inhibit protein synthesis thus causing cell death or apoptosis [47]. Several crop plants including legumes contains various bioactive compounds such as flavonoids, phenols and some peptides that can efficiently scavenge ROS thus ameliorating stress induced oxidative damages [48]. Flavonoids such as flavanones and flavon-3-ols present in the seeds of certain leguminous plants such soybean and hyacinth bean have been reported to have antioxidative effect as demonstrated by both animal and cell culture studies [49]. In a study conducted by Babu et al. [50] oral infusion of flavanones and flavon-3-ols to an alloxan induced insulin dependent diabetic mouse, significantly enhanced the activity of hepatic catalase, superoxide dismutase and glutathione reductase enzymes thereby confirming their function as antioxidants. Similarly, in another study, researchers orally administered a flavonoid rich compound apigenin to streptozotocin-induced diabetic rats that significant reduction in the triglyceride levels which could be due the antioxidative effect of apigenin that effectively maintained ion/osmotic homeostasis [51]. Moreover, like apigenin, researchers also used anthocyanidin and luteolin treatment to diabetic rats which ultimately protected rat cells from oxidative damage via controlling the synthesis of iterlukin-1β and interferon-γ [52]. Like other flavonoids, anthocyanidin is also extensively present in legume plants which have received significant recognition owing to their health benefits and potential antioxidative properties [52].

Antioxidant peptides like His-Trp-Tyr-Lys have demonstrated to play exceptional role in ameliorating stress induce oxidative damage by efficiently regulating the scavenging of ROS [53]. Moreover, several studies have shown that thiol group of Cys residue can efficiently chelate metallic ions thus lowering the effect of oxidative stress and minimising the onset of chronic disease [53]. A study conducted by Morales-Medina et al. [54] reported that Val and Leu residues present at N-terminus of a peptide and Tyr and Trp residues present at C-terminus of same peptide have antioxidative properties that were effective in minimising lipid peroxidation and strengthening ion homeostasis. Furthermore, it is also well documented that seeds and leaves of legume plants are rich source of other bioactive compounds such as anthocyanins, polyphenols with antioxidative properties and are also capable of performing metal sequestration and stimulate the expression of other stress responsive genes [55]. Additionally, Zhu et al. [56] evaluated various other peptides from

soybean and wheat having Leu-Leu-Pro-His-His repeat for its antioxidative activity by using distinct experimental procedure and conditions. The results indicated that the peptide was effective in stimulating 1,1-diphenyl-2-picrylhydrazyl (DPPH) activity, expression of enzymatic and non-enzymatic antioxidants such as catalase, superoxide dismutase, peroxidase and ascorbate thus controlling the level of ROS generation and minimising the chance of severe disease. Lunasin peptide found in soybean and other legume has also been extensively investigated for its antioxidative properties where the researchers documented that lunasin was effective in scavenging both hydrogen peroxide and superoxide anion thereby protecting cell from oxidative damage [42].

#### **2.6 Cytotoxic properties**

Since ancient times legumes have been ascribed to have pharmaceutical/therapeutic values far beyond than providing essential nutrition in the form of amino acids [57]. In recent years, various proteins/peptides form several legume species have been included in the category of nutraceuticals i.e., food or products derived from them having medicinal or therapeutic role in the prevention of disease along with nutritional benefits [57]. Various legume-based bioactive proteins/peptides have been isolated and characterised for their functional role such as Bowman-Birk inhibitors (BBIs), Kunitz inhibitors (KIs) and alpha amylase inhibitors (AAIs) which are also commonly known as anti-nutritional compounds [58]. Several researchers during their early epidemiological studies observed that the protease such as Bowman-Birk inhibitors isolated from soybean seeds were highly effective in the counteracting tumour growth under both *in vitro* and *in vivo* conditions [58]. Later, these inhibitors also demonstrated their involvement in the treatment of hypocholesteraemia, cell toxicity, lowering of blood glucose level and pressure. The BBIs are distributed across many plant species including fruits and vegetables which are characterised by the presence of conserved pattern of 14 cysteine residues forming disulphide linkages having multigene origin. An exceptional property of these protease inhibitors is that they are structurally and functionally stable under changing environment conditions and can effectively bind to IgE thus embarking their anti-proliferative effect in gut mucosa and colon cancer thereby keeping cellular toxicity at a bay [59]. Additionally, researchers have isolated and purified these inhibitors from liver, kidney and lungs to understand their mechanism of action however, their course of action is still under debate [60].

Furthermore, AAIs have demonstrated themselves has a suitable candidate for controlling triglyceride levels thus keeping obesity under check whereas lectins obtained from the seeds of legumes have also shown immense therapeutic potential displaying cytotoxic and anti-cancer activity [60]. For example, concanavalin lectin obtained from the seeds of *Canavalia ensiformis* L. are structurally stable and are highly resistant to denaturation and in vivo proteolysis displaying strong antihepatoma activity under acidic conditions [61]. The cytotoxic and anti-cancer activity of lectins have also been demonstrated using animal model where internalisation of lectins in small intestine showed stimulation in immune and hormonal activity thus confirming their role as therapeutic agents. Researchers in last few years have identified and characterised AAIs from soybean and *Phaseolus vulgaris* for clinical studies and obtained interesting outcome as AAIs were effective in controlling obesity and blood glucose level in hypercholesterolemic rat model [60]. Similarly, α-subunit of soybean 7S globulin protein has been well ascribed to stimulate the transcription of HepT9A4 hepatic cells thus increasing low density lipoprotein (LDL) uptake in HepG2 cells in hypercholesterolemic rat model [62]. However, the involvement of these protease inhibitors and lectins in the treatment of various chronic diseases are mainly confined to in vitro studies or animal model, therefore, efforts are needed

#### *Unlocking Pharmacological and Therapeutic Potential of Hyacinth Bean (*Lablab purpureus *L.)… DOI: http://dx.doi.org/10.5772/intechopen.99345*

to increase the dimension of their application by performing more human clinical trials [63]. Furthermore, efforts are also being diverted towards the identification of these medicinally important bioactive compounds in underutilised legumes such as hyacinth bean for increasing the bioavailability of these bioactive compounds for the benefit of mankind.
