New polyesterified triterpenes from the stems of maesa membranacea and their α -glucosidase inhibitory activities

A phytochemical investigation of the ethyl acetate extract from the stems of Maesa membranacea A. DC. resulted in the isolation of three polyesterified ursane-type triterpenes including two new derivatives (1 - 2), and one previously reported (3). Their chemical structures were determined based on the HR-ESI-MS and NMR spectroscopic data. In the α-glucosidase activity assay, MeOH extract of M. membranacea showed strong inhibition of the enzyme with an IC50 value of 2.64 ± 0.06 μg/mL. Compounds 1 and 3 significantly inhibited α-glucosidase activity with IC50 values of 25.39 ± 1.15 μg/mL and 21.71 ± 1.48 μg/mL, respectively. A molecular docking study of compounds 1 and 3 with α-glucosidase enzyme has suggested that these compounds bind to the enzyme at an allosteric site.