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

Abstract

The bark and heartwood extractives of the blackwattle tree (Acacia Moll88ima) both contain mix- tures of complex polyphenolic compounds con- sisting of a molecular-weight gradation within the range 300-3000 (Roux & Evelyn, 1958a, c). Keppler (1957) showed that wattle-heartwood ex- tractives contain a (+ )-7:3':4'-trihydroxyflavan-3:4-diol, which appears to be the prototype and possible precursor of some of the condensed tannins of the wood (Roux, 1958 b), and which was found to be enantiomorphous (Clark-Lewis & Roux, 1958, 1959) with a similar monomeric (-)-leuco-fisetinidin prototype of quebracho (Schinop8i8 balan8ae and S. quebracho-colorado) heartwood tnins (Roux, 1958a; Freudenberg & Weinges, 1958; Roux & Evelyn, 1958b). Roux & Maihs (1958) have briefly reported the isolation from the fresh bark extract of (-)-7:3':4':5'-tetrahydroxyflavan-3-ol, in addition to (+ )-catechin and (+ )-gallocatechin. The present study provides details of the isolation, characterization and estimation of these catechins.