Proanthocyanidins in common food products of plant origin.

The contents of extractable and unextractable proanthocyanidins were determined in a large number of commercial food products of plant origin available in Finland. Proanthocyanidins were extracted with aqueous acetone-methanol and quantified by normal phase high-performance liquid chromatography (HPLC) according to their degree of polymerization. Unextractable proanthocyanidins were analyzed from the extraction residue by reversed phase HPLC after acid-catalyzed depolymerization as free flavan-3-ols (terminal units) and benzylthioethers (extension units). Proanthocyanidins were detected in 49 of 99 selected food items. The highest contents per fresh weight were determined in chokeberries, rose hips, and cocoa products. Berries and fruits were generally the best sources of proanthocyanidins, whereas most of the vegetables, roots, and cereals lacked them completely. Many of the samples contained a significant proportion of insoluble proanthocyanidins, which need to be quantified as well if total proanthocyanidins are studied. Considerable variation was observed in proanthocyanidin contents in berries, which requires further research.