Anti-glycation Properties and Antioxidant Activities of Moringa oleifera Seed Protein Hydrolysate Fractions Obtained from Trypsin Proteolysis

Abstract

Proteins from Moringa oleifera were extracted via alkaline solubilization followed by acid precipitation. They were then subjected to hydrolysis using trypsin and the resulting hydrolysates separated into <1kD, 1-3kD and 3-5kD peptide fractions by means of size exclusion chromatography. The hydrolysate and the peptide fractions were evaluated for their effects on hemoglobin glycation and four free radical systems – DPPH radicals, ferric ions, hydroxyl radicals and superoxide radicals. Results revealed that the peptides inhibited hemoglobin glycation in a synergistic manner, as the unfractionated hydrolysate slowed down the formation of glycated hemoglobin better than the constituent fractions (IC50 = 0.163 ± 0.028 mg/mL). Peptide fraction 3, Ft3, demonstrated the best activities against DPPH radical, ferric ions and superoxide radicals (35.764 ± 1.933%, 44.709 ± 0.676 mM Fe2+ and 92.223 ± 1.794% respectively) whereas fraction 2, Ft2, scavenged hydroxyl radicals better than other fractions (82.000 ± 1.155%). This suggested a direct relationship between average molecular weights of these peptide fractions and their antioxidant abilities, such that peptide fractions with higher molecular weights had better capacities to neutralize free radicals. It is concluded that M. oleifera seed proteins may encode potentially bioactive peptides, which could be optimized for the development of food additives and peptide-based therapeutic alternatives in the management of diabetes mellitus.