Four new flavonol glycosides from the leaves of Ginkgo biloba.

Four new flavonol glycosides, 5, 7, 5'-trihydroxy-3', 4'-dimethoxyflavonol-3-O-α-L-rhamnopyranosyl-(1→6)-ß-D-glucopyranoside (1), quercetin 3-O-(6-trans-feruloyl)-ß-D-glucopyranosyl-(1→2)-α-L-rhamnopyranoside (2), kaempferol 3-O-(6-trans-caffeoyl)-ß-D-glucopyranosyl-(1→2)-α-L-rhamnopyranoside (3), myricetin 3-O-(6-trans-p-coumaroyl)-ß-D-glucopyranosyl-(1→2)-α-L-rhamnopyranoside (4), together with nine known flavonoids and two known lignans, were isolated from the leaves of Ginkgo biloba. Their structures were determined by extensive spectroscopic analyses. Their cardioprotective effects against H2O2-induced apoptosis in H9c2 cells were also evaluated. The flavonol glycosides had stronger activity than the acylated flavonol glycosides at the concentration of 50 µM.