Flavans and A-type proanthocyanidins from Prunus prostrata

Abstract

A new natural dimeric A-type proanthocyanidin and two new monomeric flavanols have been isolated from Prunus prostrata and identified as ent- epiafzelechin (2α → O → 7, 4α → 8) quercetin, 5,7,2',5'-tetrahydroxy- (2R,3R)-flavan-3-ol and, 7-methoxy-(+)-catechin, respectively. The structurally related metabolites ent-epiafzelechin (2α → O → 7, 4α → 8) afzelechin, ent-epiafzelechin (2α → O → 7, 4α → 8) kaempferol, ent- epiafzelechin (2α → O → 7, 4α → 8) epicatechin, ent-epiafzelechin (2α → O → 7, 4α → 8) epiafzelechin, ent-epiafzelechin (2α → O → 7, 4α → 8) catechin, (+)-catechin and (-)-epicatechin were also isolated. Structure elucidation was achieved by extensive NMR (homo- and hetero-nuclear two- dimensional correlation, NOE difference, and selective INEPT experiments) and CD studies.