The α-glucosidase inhibiting isoflavones isolated from Belamcanda chinensis leaf extract

I The dried rhizome of Belamcanda chinensis is an important Chinese traditional medicine used for the treatment of inflammation and many other disorders. Previously, we reported the hypo- and antihyper-glycemic effects of the aqueous leaf extract of B. chinensis (BCL) and identified the isoflavones as its principal active fraction. In the present study, the α-glucosidase inhibitory effect of BCL and its rough isoflavone preparation (BIF) was tested in vitro and in vivo. Thirteen isoflavones were isolated from BCL and their α-glucosidase inhibitory activity was screened in vitro. The results showed that BCL (500 and 1000 mg/kg) and BIF (250 and 500 mg/kg) greatly inhibited the increase in blood glucose level after 5 g/kg starch loading in normal mice. Six out of the thirteen isoflavones (swertisin, 2 ” -O-rhamnosylswertisin, genistein, genistin, mangiferin and daidzin) exhibited strong α-glucosidase inhibitory activity in vitro. HPLC analysis showed that swertisin was the most abundant isoflavone in BCL accounting for 1.24% of BCL, 7.44% of BIF, and 11.24% of the total isoflavone fraction of BCL, respectively. These results demonstrate that BCL possesses significant α-glucosidase inhibitory activity and swertisin may be the principal active component of BCL in α-glucosidase inhibition.