Prototypes of black wattle tannins and their stereochemistry

Abstract

A number of interrelated flavonoid compounds, present in trace quantities in mature black wattle (Acacia mearnsii De Wild) bark, have been isolated and identified for the first time. They include a) the resorcinol-pyrogallol analogues, (+)-leuco-robinetinidin (7,5',4',5'-tetrahydroxyflavan-3,4-diol), dihydrorobinetin (7,5',4',5'-tetrahydroxyflavan-3-ol-4-one) and robtein (2',4',5,4,5- pentahydroxychalcone) and b) the resorcinol-catechol analogues, (+)-leuco-fisetinidin (7,3',4'-trihydroxyflavan-3,4-diol), fustin (7,3',4'-trihydroxyflavan-3-ol-4-one), (-)-fisetinidol (7,3',4'trihydroxyflavan- 3-ol), butein (2',4',3,4-tetrahydroxychalcone) and butin (7,5',4'-trihydroxyflavan-4-one). In addition, two flavonol glycosides, myricitrin (3,5,7,3',4',5'-hexahydroxyflavone-3-rhamnoside ) and quercitrin (5,5,7,5',4'-pentahydroxyflavone-3-rhamnoside), which belong to the phloroglucinol-pyrogallol and phloroglucinolcatechol class of flavonoids respectively, were isolated from immature bark. These represent the only glycosides isolated hitherto from wattle bark or heartwood extracts. Summary, p. i.