A new triterpenoid pentaglycoside from Olax imbricata: isolation and in vitro, in silico studies on α-glucosidase.

Extensive fractionation of methanol extract from the dried powdered roots of Olax imbricata (Olacaceae) led to the isolation of a new oleanane-skeleton triterpene pentaglycoside, olaximpentaose (1). The chemical structure was elucidated using 1D and 2D NMR and HR-ESI-MS data analysis. The sugar subunits of olaximpentaose (1) were determined by acidic hydrolysis and 1H NMR chemical shifts, coupling constants, and integral ratios of the anomeric signals. Compound 1 exhibited the higher inhibition against α-glucosidase, with the IC50 = 97.19 ± 12.29 µM when compared with acarbose (IC50 = 126.62 ± 5.57 µM). In addition, the docking results revealed that structure 1 and acarbose were bound to the enzyme with docking scores of -8.960 kcal/mol and -7.966 kcal/mol, respectively. Molecular dynamics (MD) simulations provided insights into the action of 1 on α-glucosidase. Following the production MD run for 100 ns, the resultant trajectories revealed that the α-glucosidase/1 complex displayed overall stability during simulations. These results might be responsible for the promising activity of 1 against α-glucosidase.