Condensed proanthocyanidins of fababeans

Abstract

Abstract Condensed proanthocyanidins were extracted from fababean hulls with water. The aqueous extract, after deproteinisation by freezing, thawing and acetone precipitation, was purified by chromatography using Sephadex LH20 gel and 95% ethanol developing solvent. Gradient chromatography of the purified condensed proanthocyanidins using 95% ethanol‐(50% v/v)acetone‐water with a Sephadex LH20 column yielded two peaks when the column effluent was monitored at 400 nm. Chromatographic behaviour before and after oxygen treatment indicated certain structural differences between fractions collected under the major peak. There were also considerable differences between the chromatographic properties of material collected from under the major peak and under the minor peak. Solvolysis experiments on the various fractions yielded differences in delphinidin: cyanidin and delphinidin: phlobaphene ratios. There were also differences in ‘tannin’ contents (determined by acidified vanillin methods) and all these differences confirmed that there were structural dissimilarities between the fractions. Tannin determinations made on the hulls of seven different cultivars of fababeans indicated condensed proanthocyanidin levels between 0–6%.