Peptide Fractions from Chymotrypsin-hydrolyzed Moringa oleifera Seed Proteins Inhibit α-amylase and α-glucosidase in vitro

Abstract

This study attempts to investigate the activities of chymotrypsin-digested M. oleifera seed proteins and their peptide fractions on carbohydrate-hydrolyzing enzymes. Proteins from M. oleifera seeds were isolated using isoelectric point precipitation and hydrolyzed using chymotrypsin. The hydrolysates obtained were fractionated into peptide fractions of <1 kD, 1-3 kD and 3-5 kD ranges by means of gel-filtration chromatography. The inhibitory effects of the hydrolysates and their fractions on α-amylase and α-glucosidase were evaluated, and kinetics of inhibition were also determined. Using starch and p-nitrophenyl glucopyranoside as substrates, the hydrolysate and fractions demonstrated concentration-dependent inhibition of α-amylase and α-glucosidase respectively (IC50 of 0.172 ± 0.005 mg mL-1 to 1.312 ± 0.267 mg mL-1, for α-amylase inhibition and IC50 of 0.463 ± 0.008 mg mL-1 to 0.696 ± 0.051 mg mL-1 for α-glucosidase inhibition). Kinetic analysis revealed that selected hydrolysate fractions competitively inhibited α-amylase while displaying a mixed mode of inhibition of α-glucosidase. This study suggests that subjecting M. oleifera seed proteins to proteolysis could yield therapeutic peptide products having immense potentials that could be harnessed to develop novel anti-diabetic agents and additives to food, which could serve as cost effective alternatives to current therapies.
Keywords: Moringa oleifera, hydrolysate, peptide, chymotrypsin, α-amylase, α-glucosidase