Inhibitory Effect of Garcinia kola Heckel (Clusiacea) Seed Extracts on Some Key Enzymes Linked to Diabetes Mellitus

Abstract

Enzymes linked with diabetes mellitus and Phytochemical characterization of its bioactive constituents. Crude n-hexane, ethyl acetate and methanol extracts were prepared successively in a soxhlet apparatus at 50ºC. Subsequently, extraction of crude enzymes from porcine pancreas and rat intestine, thin layer chromatographic analysis (TLC), and inhibitory effects of the extracts on b-amylase and b-glucosidase were determined in vitro. The results reveal that G. kola seed extracts inhibited b-amylase (IC₅₀=  4.89 mg/ml, 3.44 mg/ml, 0.78 mg/ml) and b-glucosidase (IC₅₀= 10.29 mg/ml, 1.68 mg/ml, 2.67 mg/ ml) corresponding to n-hexane, ethyl acetate, methanol gradient extracts. n-hexane extract had the highest inhibitory effect on b-amylase, while methanol extract was highest on b-glucosidase. Characterization of the bioactive constituents of the extracts using TLC analysis revealed the presence of steroids/triterpenes and phenolic compounds with phenolic compounds appearing in all extracts irrespective of the solvent polarity used for extraction. Anthraquinone and alkaloids were confirmed absent on TLC. This enzyme inhibition could be one of the possible pathways by which G. kola elicits its antidiabetic properties. Furthermore, the enzyme inhibitory properties of the extracts can be attributed to the presence of steroids/triterpenes, phenolic compounds in the seeds of G. kola.

Keywords: Garcinia kola, b-amylase, b-glucosidase, TLC, Inhibitory Effect