Inhibitory Potentials of Hunteria umbellata Seed Extracts on Some Key Enzymes of Diabetes Mellitus with Profiling of its Phenolic Constituents

Abstract

Background: The seeds of Hunteria umbellatais a common folkloric plant used in the management of Diabetes mellitus in Nigeria. Though there are many reports on its antidiabetic potential, there is a scarcity of information on its mechanisms of antidiabetic action. This study was designed to investigate the mechanism of antidiabetic action of H. umbellata seed by evaluating the inhibitory effect of its extracts on enzymes that are targeted in the management of diabetes mellitus. Methods: Dried seeds of H. umbellata were powdered and extracted separately in water and ethanol. Alpha-amylase, α-glucosidase, and sorbitol dehydrogenase inhibitory activities of the concentrated extracts were determined spectrophotometrically. Furthermore, the phenolic profile of the seed was determined using HPLC-UV analysis. Results: The inhibitory effect of both ethanol and aqueous extracts H. umbellataon the selected enzymes were similar with IC50 value of 40.36 ± 2.92 and 40.25 ± 4.53 mg/mL for α-amylase, 45.42 ±2.44 and 39.32 ± 3.46 mg/mL for α-glucosidase, and 36.25 ± 2.31 and 32.35 ± 1.53 mg/mL for sorbitol dehydrogenase, respectively. Kinetic studies showed that α-amylase was inhibited competitively, while both α-glucosidase and sorbitol dehydrogenase were inhibited in a non-competitive manner. The phenolic compounds identified in the H. umbellata seed were gallic acid, catechin, p-coumaric acid, rutin, and ferulic acid. Conclusion: The H. umbellata seed extract’s antidiabetic action may be by inhibiting the activities of α-amylase, α-glucosidase, and sorbitol dehydrogenase. This inhibition could be due to the presence of phytochemicals such as phenolic compounds in the plant.