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 (2 α → O → 7, 4 α → 8) quercetin, 5,7,2′,5′-tetrahydroxy-(2 R,3 R)- flavan-3-ol and, 7-methoxy-(+)-catechin, respectively. The structurally related metabolites ent-epiafzelechin (2 α → O → 7, 4 α → 8) afzelechin, ent-epiafzelechin (2 α → O → 7, 4 α → 8) kaempferol, ent-epiafzelechin (2 α → O → 7, 4 α → 8) epicatechin, ent-epiafzelechin (2 α → O → 7, 4 α → 8) epiafzelechin, ent-epiafzelechin (2 α → O → 7, 4 α → 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.