Qualitative analysis and HPLC isolation and identification of procyanidins from Vicia faba

The soluble proanthocyanidins of the coloured seed coats of Vicia faba L. were isolated and separated by solvent partition. The chemical characteristics of the proanthocyanidins were elucidated by total oxidation and partial degradation in the presence of phloroglucinol followed by HPLC analysis. The native extract of proanthocyanidins contained (+)-gallocatechin, (-)-epigallocatechin, (+)-catechin and (-)-epicatechin units. Oligomeric procyanidins were purified by chromatography on Sephadex LH-20 and the accessible compounds were isolated by RP-HPLC using a Licrospher Li 100 Column. The structures of the purified oligomeric procyanidins were elucidated using a procedure involving TLC, UV spectroscopy, ESI-MS and HPLC analysis of the products from the phloroglucinol reaction. The major condensed tannins of Vicia faba comprise six compounds identified as two A-type procyanidin dimers, the procyanidin dimers B1, B2 and B3, and a procyanidin trimer.