OLIGOMERIC FLAVANOIDS .16. NOVEL PROROBINETINIDINS AND THE 1ST A-TYPEPROANTHOCYANIDIN WITH A 5-DEOXY A-RING AND A 3,4-CIS C-RING FROM THE MAIDEN INVESTIGATION OF COMMERCIAL WATTLE BARK EXTRACT

Structural examination of the phenolic metabolites of commercially use d wattle bark extract reveals the presence of a range of novel flavano ids comprising (-)-epirobinetinidol 1, the first C-methyl proanthocyan idin, (-)-fisetinidol-(4alpha,8)-6-methyl-(+)-catechin 3, the first pr orobinetinidins with 3,4-cis C-ring configurations 7 and 9, and the un ique A-type prorobinetinidin 11 representing the first entry amongst t his class of oligoflavanoids exhibiting a 5-deoxy A- and a 3,4-cis C-r ing. They are accompanied by a range of functionalized prorobinetinidi n-type tetrahydropyrano[2,3-f]chromenes 20, 23, 25 and 28 and the trim eric 'isomerization-intermediate' 32, all exhibiting the characteristi c structural features that are essential for the use of 'Mimosa' extra ct in cold-setting adhesives and leather-tanning applications. In addi tion, evidence demonstrating that the dynamic A-E conformational equil ibrium of flavan-3-ol moieties in condensed tannins may be influenced by external factors is presented.