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

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