Flavonoid Constituents of Zingiber zerumbet Smith

Two flavonoid glycosides (6 and 7) and two flavonols (3 and 4) were isolated from the CH2Cl2-soluble part of the extract of fresh rhizomes of Zingiber zerumbet Smith, along with zerumbone (1), zerumbone epoxide (2) and curcumin (5). The structures of the isolated compounds were determined to be kaempferol-3,4′-O-dimethylether (3), kaempferol-3-O-methylether (4), kaempferol-3-O-(3,4-O-diacetyl-α-l-rhamnopyranoside) (6) and kaempferol-3-O-(2,4-O-diacetyl-α-l-rhamnopyranoside) (7). The stability of the two flavonoid glycosides (6 and 7) and their occurrence in the fresh rhizome are also discussed.