Oleanolic acid as a potential antidiabetic component of Xylopia aethiopica (Dunal) A. Rich. (Annonaceae) fruit: bioassay guided isolation and molecular docking studies

The present study was designed to conduct the bioassay-guided isolation of possible bioactive compound(s) responsible for the antidiabetic action of Xylopia aethiopica (Dunal) A. Rich. fruit. The isolation of compound was guided by α-glycosidase and α-amylase inhibitory activities. Molecular docking with Autodock Vina was used to decipher the mode of interaction and binding affinity of the possible compound(s) with the selected enzymes. A pentacyclic triterpene, oleanolic acid (OA) was isolated from fruit and exhibited significantly (p < 0.05) lower IC50 values (α-amylase: 89.02 ± 1.12 µM, α-glucosidase: 46.05 ± 0.25 µM) than other fractions and the acarbose. Interestingly, OA was found to bind to the α-amylase and α-glucosidase with minimum binding energy values of -0.9 and -1.2 kcal/mol respectively and none of the interactions involved hydrogen bond formation. Data of this study suggest that OA is responsible for the antidiabetic action of X. aethiopica fruit through the inhibition of α-amylase and α-glucosidase enzyme activities.