Kaempferol tetraglucosides from cabbage leaves

Four flavonol glycosides were isolated from a leaf extract of cabbage and characterized by chemical and spectroscopic methods including 1H and 13C NMR and negative ion FAB-MS. The common structure of the four compounds was kaempferol 3-O-beta-D-[beta-D-glucopyranosyl(1-->2)glucopyranoside]-7- O-beta-D-[beta-D-glucopyranosyl(1-->4)glucopyranoside]. This compound was found unmodified or acylated at C-2"' (outer glucose in sophorosyl moiety) with either sinapic acid, ferulic acid or caffeic acid. The possible role of diversity in glycosylation and acylation patterns of flavonol glycosides for plant defences against herbivores is discussed.