Isolation and identification of α-glucosidase inhibitors from the stem bark of the nutgall tree (Rhus javanica Linné)

Abstract

Ethyl acetate (EtOAc) layer obtained after the solvent fractionation of hot water extracts from nutgall tree (Rhus javanica) stem bark showed higher α-glucosidase inhibition activity than other layers. A novel acetophenone glucoside (4) and six known phenolic compounds were isolated from the EtOAc layer. The structure of 4 was determined to be 3,4,5-trihydroxyacetophenone 4-O-β-d-glucopyranoside. The six known compounds were identified as gallic acid (1), 5-methylresorcinol (2), methylgallate (3), 3-hydroxy-5-methylphenol 1-O-β-d-(6′-galloyl)glucopyranoside (5), scopoletin (6), and phlorizin (7). Their chemical structures were determined by electrospray ionization mass spectrometry and nuclear magnetic resonance analyses. Compound 5 was newly identified from this plant. Compounds 6 and 7 showed significantly higher α-glucosidase inhibition activity than other compounds.