Acylated glucosylflavones as α-glucosidase inhibitors from Tinospora crispa leaf.

The ethanolic extract of Tinospora crispa leaf had shown inhibitory activity toward α-glucosidase. Bioassay guided fractionation and separation of this extract led to the isolation of 17 flavonoids. Among them, four acylated glycosylflavonoids (6, 8, 9, 15) are new compounds. Their structures were elucidated on the basis of spectroscopic analysis. Among the isolated compounds, isovitexin 2″-(E)-p-coumarate (8) showed the best activity against α-glucosidase with an IC50 value of 4.3±1.4μM. However, isoorientin 2″-(E)-p-coumarate (7), the 3'-hydroxylated 8, is much less active (IC50 35.7μM). Such significant difference was rationalized by CAD study on α-glucosidase.