Multifunctional Bioactive Peptides from Germinated Soy (Glycin max) and Voandzou (Vigna subterranea) Beans: In-vitro Anti-Diabetic Potential through α-amylase α-glucosidase Inhibition, and Antioxidant Ability by DPPH Reducing

Abstract

Legumes, protein-rich foods containing various peptides, offer the possibility of modulating both sugar absorption and free radical production, in order to prevent diabetes and oxidative stress diseases. This study aimed to reveal the antioxidant and anti-diabetic potential of peptides from germinated soy and voandzou beans by checking the efficacy of these beans peptides generated by germination and even after post-meal digestion. Thus, beans crude proteins were extracted and digested with pepsin and pancreatic enzymes. Digested proteins were fractioned by dialysis. Each type of proteins ability to inhibit α-amylase and α-glucosidase activity and to scavenge DPPH free radical, were tested. Total protein content determined by spectrophotometry at 241 nm and extraction yield evaluated showed no significant difference (p˂ 0.05) with an average of 88% (soy) and 86% (voandzou) and 64.43% (soy) and 60.30% (voandzou), respectively; as opposed to the soluble protein content assessed in the supernatant of protein isolates. Simulated digestion of isolate protein generated peptide extracts showed a better inhibitory capacity of α-amylase and α-glucosidase with the digested voandzou protein isolate D2 exhibiting optimum inhibition (72.39%) for α-glucosidase near to acarbose (75.99%) and the digested soy protein isolate D2 displaying the optimum inhibition (89.25%) for α-amylase better than acarbose (75.99%). Moreover, it is the external fractions of size inferior to 10 kDa which are endowed with this excellent capacity of inhibition of these enzymes involved in the regulation of postprandial glucose. Finally, the high DPPH free radical scavenging capacity of all germinated protein isolate between 64.72 (D0) and 72.27% (D2) for soy and 73.45 (D0) and 81.43 % (D4) for voandzou is practically maintained after digestion and dialysis. Germinated soy and voandzou seeds thus have shown promising potential for being used as nutraceutical or functional ingredients for treatment and prevention of diabetes and diseases related to oxidative stress.