Inhibitory Activity of Protein Isolate from Bambara Groundnut (Vigna subterranean) on Alpha-amylase and Pancreatic Lipase

Abstract

Aim: This research was carried out to examine the inhibitory activity of protein isolate from bambara groundnut on alpha-amylase and lipase in vitro, and to study the effect of temperature, pH and substrate concentration on the enzymes in vitro. Place and Duration of Study: Department of Biochemistry, Lagos State University, Ojo, Lagos, Nigeria between August 2019 and January 2020. Methodology: Protein was isolated from bambara groundnut using alkaline extraction (isoelectric precipitation). Alpha-amylase and pancreatic lipase inhibitory assays were performed using starch solution and a stock solution of PNPB (p-nitrophenyl butyrate) as substrates respectively. The effect of variation of substrate concentration, temperature and pH on the inhibition of alpha-amylase and pancreatic lipase activity was also studied. Results: At a concentration of 1.0 mg/mL, the protein isolate from Bambara groundnut exhibited 91% inhibition of alpha-amylase activity with an IC50value of 0.40±1.85 mg/mL (in comparison with acarbose which exhibited 86% inhibition at the same concentration) and 91% inhibition of lipase activity with an IC50value of 0.73±3.7 mg/mL (in comparison with Orlistat which exhibited 97%  inhibitionat the same concentration). The most favorable temperature for the inhibition of alpha-amylase and lipase was 40°C. The optimum pH for alpha-amylase and lipase inhibitory activity was 10.5 and 9.0 respectively. Conclusion: These results showed the presence of alpha-amylase and pancreatic lipase inhibitors in bambara groundnut which indicates that this plant can be used as a feed supplement in the control of high blood-glucose level of diabetes patients.