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

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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.