In vitro Angiotesin-1-converting enzyme, α-amylase and α-glucosidase inhibitory and antioxidant activities of Luffa cylindrical (L.) M. Roem seed protein hydrolysate

In recent times, researchers have explored food derived peptides to circumvent the side effects of synthetic drugs. This study therefore examined the amino acid constituents, in vitro antioxidant activities, angiotensin-1converting enzyme (ACE), alpha-glucosidase and alpha-amylase inhibition kinetics of protein hydrolysate obtained from the seed of Luffa cylindrica. The peptide yield by pepsin (16.93 +/- 0.28%) and trypsin (13.20 +/- 1.02%) were significantly lower than that of Alcalase (34.04 +/- 1.96%). Alcalase hydrolysate however displayed the highest ferric reducing antioxidant capacity (FRAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and H2O2 scavenging activities (0.63%, 85.88% and 41.69% respectively), while the highest superoxide scavenging activity was shown by peptic hydrolysate (57.89%). The ACE inhibition by the hydrolysates with IC50 of 0.32 -0.93 mg/mL, increased as the concentration of the peptic hydrolysate increased with the highest ACE-inhibitory activity (74.99 +/- 0.43%) at 1.2 mg/mL of peptic hydrolysate. Tryptic and Alcalase hydrloysates exhibited a strong alpha-amylase inhibition having 27.96 +/- 0.06% and 36.36 +/- 0.71% inhibitory capacity respectively with IC50 of 1.02 -3.31 mg/mL. Alcalase hydrolysates demonstrated the strongest inhibition (65.81 +/- 1.95%), followed by tryptic hydrolysates (54.53 +/- 0.52%) in a concentration-dependent inhibition of alpha-glucosidase (IC50, 0.48 -0.80 mg/mL). Kinetic analysis showed that ACE-inhibition by different concentrations of Alcalase, pepsin and trypsin hydrolysates is uncompetitive, mixed-type and non-competitive respectively. alpha-Amylase was non-competitively inhibited while alpha-glucosidase was un-competitively inhibited by all the hydrolysates. The total amino acid concentration for Alcalase, trypsin and pepsin hydrolysates was 53.51g/100g, 75.40g/100g and 85.42g/100g of Luffa cylindrica seed protein hydrolysate respectively, with glutamate being the most concentrated essential amino acid in all the three hydrolysates. From these results, it can be deduced that Luffa cylindrica seed Alcalase and tryptic protein hydrolysates may play critical and indispensible role as bio-tools in diabetes and hypertension treatment.