Free Radical Scavenging-Related Antioxidant Properties and Inhibitory Activities of Telfairia occidentalis Seed Protein Hydrolysates and Peptide Fractions Against Two key Enzymes Implicated in Diabetes Mellitus

This study aimed to appraise the in vitro antioxidant and antidiabetic activities of protein hydrolysates and peptide fractions obtained from Telfairia occidentalis (T. occidentalis) seeds. The seed protein was extracted and hydrolysed using pepsin (pepTOSPH), alcalase (alcTOSPH) and pancreatin (panTOSPH) according to standard protocols. The pepTOSPH hydrolysate was also fractionated into < 7 and < 10 kDa peptide fractions by ultrafiltration method. T. occidentalis seed protein extract obtained contained 86.50% protein with 18 different amino acids. The degree of hydrolysis by pepTOSPH (56.07 & PLUSMN; 0.07%) and panTOSPH (50.20 & PLUSMN; 1.06%) were significantly (p < 0.05) higher than that of alcTOSPH (47.05 & PLUSMN; 0.14%). Also, the hydrolysates and peptide fractions demonstrated NO and DPPH scavenging activities significantly (p < 0.05) as well as ferric reducing antioxidant potential (FRAP) in concentration-dependent manners. Furthermore, the hydrolysates exhibited a significant (p < 0.05) inhibitory activity against & alpha;-amylase with their respective IC50 as pepTOSPH (1.03 mg/mL), panTOSPH (1.20 mg/mL), alcTOSPH (1.31 mg/mL) and & alpha;-glucosidase (IC50; pepTOSPH = 0.85 mg/mL; panTOSPH = 1.40 mg/mL; alcTOSPH = 1.58 mg/mL), while peptide fractions demonstrated inhibitory activity against & alpha;-amylase with IC50 as < 7 kDa = 0.35 mg/mL and < 10 kDa = 0.75 mg/mL and against & alpha;-glucosidase with IC50 as < 7 kDa = 0.37 mg/mL and < 10 kDa = 0.62 mg/mL. The findings from this study indicate that the hydrolysates and its < 7 kDa peptide fraction demonstrated potential antioxidant and antidiabetic activities. Therefore, T. occidentalis seed protein and peptide fractions could be advantageous for the nutraceutical management of diabetes mellitus.