Condensed tannins. 13. Interrelationships of flavonoid components from the heartwood of Robinia pseudacacia

Abstract

Flavonoid components from the heartwood and sapwood of Robinia pseudacacia have been isolated and their concentrations have been estimated. The predominant flavonoids and resorcinol-pyrogallol analogues, (+)-7, 3[image], 4[image], 5[image]-tetrahydroxy-flavan-3, 4-diol, ([long dash])-robinetinidol, (+)-dihydrorobinetin (partly racemic), ([long dash])-7,3[image] , 4[image], 5[image]-tetrahydroxyflavanone (robtin) (partly racemic), robinetin, 2[image], 4[image], 3, 4, 5-pentahydroxychalkone (robtein), an unstable leuco-robinetinidin and polymeric leucorobinetinidin tannins. (+)-7, 3 [image], 4[image] , 5[image]-Tetrahydroxyflavan-3, 4-diol probably has a 2, 3- trans-3, 4-cis-configuration. Resorcinol-catechol analogues, (+)-7, 3[image] , 4[image]-trihydroxyflavan-3, 4-diol, (+)-fustin (partially racemic), ([long dash])-butin (partly racemic), butein and fisetin, together with traces of 2[image] , 4[image],4-trihydroxychalkone, are also present. A tentative scheme of interconversion of the predominant components is outlined.