Selective adsorption of flavonoid compounds from the leaf extract of Ginkgo bilobaL.

A simple purification method has been developed in which flavonoid compounds are selectively adsorbed onto a polycarboxyl ester resin (XAD-7) from methanol extract of ginkgo leaves. When 1.0 g dried gingko leaves was extracted with 100 ml of methanol, about 98% of total flavonoid compounds was recovered by selective adsorption. The pH did not affect the adsorption of flavonoids but at high pH the chemical structure of flavonoids was changed and the adsorption decreased to almost zero. As the solution polarity played a key role in the selective adsorption, the amount of water added to the methanol extract was critical for the recovery and loading of flavonoids. Using standard flavonoids, kaempferol and quercetin, the optimal water content was 80% and the recovery was 80% with 10 g of resin dosage/l.