The microbial metabolism of condensed (+)-catechins by rat-caecal microflora

The metabolism of 2,3-trans-3,4-trans-3,5,7,3',4'-pentahydroxy-4-(2,4,6-trihydrox yphenyl)-flavan and 2,3-trans-3,4-trans-3,5,7,3',4',-pentahydroxy-4-(2,3-trans-3,5,7,3 ', 4'-pentahydroxyflavanyl-[8])-flavan in vitro by rat-caecal microflora was investigated. Metabolites were extracted and enriched by column chromatography and preparative h.p.l.c., while structural determination was carried out using comparative g.l.c.-mass spectrometry and p.m.r. spectrometry. The metabolites identified were derivatives of benzoic acid, phenylacetic acid, phenylpropionic acid and phenyllactic acid in addition to phloroglucinol, delta-(3-hydroxyphenyl)-gamma-valerolactone and 1-(3-hydroxyphenyl)-3-(2,4,6-trihydroxyphenyl)-propan-2-ol. An additional metabolic route, which differs from the expected severance of the (+)-catechin-phloroglucinol bond and well-documented total heterocyclic ring degradation of flavanoids, is proposed.