Effect of O-methylated and glucuronosylated flavonoids from Tamarix gallica on α-glucosidase inhibitory activity: structure-activity relationship and synergistic potential.

O-Methylated and glucuronosylated flavonoids were isolated from Tamarix gallica as α-glucosidase inhibitors. Structure-activity relationship of these flavonoids suggests that catechol moiety and glucuronic acid at C-3 are factors in the increase in α-glucosidase inhibitory activity. Furthermore, rhamnetin, tamarixetin, rhamnazin, KGlcA, KGlcA-Me, QGlcA, and QGlcA-Me exhibit synergistic potential when applied with a very low concentration of acarbose to α-glucosidase from rat intestine.