New flavonol triglycosides from the leaves of soybean cultivars

Abstract

Soybean (Glycine max) is a major crop in the world. Three new flavonol 3-O-glycosides, kaempferol 3-O-α-L-rhamnopyranosyl-(1→4)-[α-L- rhamnopyranosyl- (1→6)-β-D-galactopyranoside] (1), kaempferol 3-O-α-L-rhamnopyranosyl-(1→4)-[β-D-glucopyranosyl-(1→6) -β-D-galactopyranoside] (4) and quercetin 3-O-β- D-glucopyranosyl- (1→2)-[α-L-rhamnopyranosyl-(1→6)-β-D-galactopyranoside] (5) were isolated from the leaves of soybean cultivars, together with three known compounds, kaempferol 3-O-β-D-glucopyranosyl-(1→2)-[α-L- rhamnopyranosyl-(1→6)-β-D-galactopyranoside] (2), kaempferol 3-O-β-Dglucopyranosyl-( 1→2)-[α-L-rhamnopyranosyl-(1→6)- β-D-glucopyranoside] (3) and quercetin 3-O-β-D-glucopyranosyl- (1→2)-[α-L-rhamnopyranosyl-(1→6)-β- D-glucopyranoside] (6), and also common flavonoids. The isolated compounds possess similar structures and high water solubility, and so it was hard to isolate them (in particular 5 and 6) with a normal preparative HPLC system. Their final purification was achieved by a preparative HPLC system equipped with a recycle device.