Coumaroyl flavonol glycosides from the leaves of Ginkgo biloba

Abstract

Two coumaroyl flavonol glycosides, isorhamnetin 3-O-α-l-[6‴-p-coumaroyl-(β-d)-glucopyranosyl-(1,2)-rhamnopyranoside], and kaempferol 3-O-α-l-[6‴-p-coumaroyl-(β-d)-glucopyranosyl-(1,2)-rhamnopyranoside]-7-O-β-d-glucopyranoside, were isolated from the n-BuOH extract of Ginkgo biloba leaves. These two, together with six other flavonol glycosides, kaempferol 3-O-α-l-[6‴-p-coumaroyl-(β-d)-glucopyranosyl-(1,2)-rhamnopyranoside], quercetin 3-O-α-l-[6‴-p-coumaroyl-(β-d)-glucopyranosyl-(1,2)-rhamnopyranoside], quercetin 3-O-α-l-[6‴-p-coumaroyl-(β-d)-glucopyranosyl-(1,2)-rhamnopyranoside]-7-O-β-d-glucopyranoside, quercetin 3-O-β-d-glucopyranosyl-(1-2)-α-l-rhamnopyranoside, quercetin 3-O-β-rutinoside, and quercetin 3-O-β-d-glucopyranoside, showed profound antioxidant activities in DPPH and cytochrome-c reduction assays using the HL-60 cell culture system.