Condensed tannins. 3. Isolation and estimation of (−)-7:3′:4′:5′-tetrahydroxyflavan-3-ol, (+)-catechin and (+)-gallocatechin from black-wattle-bark extract

Abstract

(-)-7:3[image]:4[image]:5[image]-Tetrahydroxyflavan-3-ol [(-)-robinetinidol] has been isolated from black-wattle-bark (Acacia mollissima) extracts in 0.3% yield. (+)-Catechin and (+)-gallocatechin were isolated in lower yields from the extracts, and ([long dash])-epicatechin has been shown to be absent from fresh-bark and commercial extracts. The concentration of the catechins in the fresh-bark extracts and in their tannin fractions is estimated by means of paper chromatography in conjunction with the measurement of maximum color density of the spots with a densitometer. The presence of (-)-robinotinidol in Acacia mollissima places further emphasis on the almost exclusive occurrence among the Leguminosae and 2 genera of the Anacardiaceae of those C15 "flavonoid" compounds of the resorcinol series which have been isolated.