Biologically active flavonoids and kava pyrones from the aqueous extract ofAlpinia zerumbet

From the aqueous extract of Alpinia zerumbet (Pers) B. L. Burttet Smith. (= Alpinia speciosa K. Schum.) flavonoids and kava pyrones were obtained. The flavonoids identified as rutin (1), kaempferol-3-O-rutinoside (2), kaempferol-3-O-glucuronide (3), (+)-catechin (4) and (−)-epicatechin (5) are well known substances that can contribute to the hypotensive, diuretic and antiulcerogenic activity of the aqueous extract of the plant, while the kava pyrones dihydro-5,6-dehydrokawain (6) and 5,6-dehydrokawain (7) have been described as antiulcerogenic and antithrombotic. The compounds were identified from their UV, 1H- and/or 13C-NMR, hydrolytic and co-TLC data. The well known activity of these compounds, which have not been previously isolated from the leaves of Alpinia zerumbet, may explain the use of the plant in the treatment of hypertension.