Proanthocyanidins (PA) in Senna alata leaves were investigated by thiolysis with benzyl mercaptan, LC-MS and NMR and consisted of almost pure propelargonidins with <6% procyanidins, had B-type linkages and a mean degree of polymerisation of three. Epiafzelechin was the major flavan-3-ol subunit (>94%) and epicatechin a minor constituent (6.4%) in residual PA and mainly detected as an extension unit.
Keywords: LC–MS; NMR; Senna alata; proanthocyanidins; propelargonidins; thiolysis; Cassia alata.