Plant proanthocyanidins. Part 4. Biosynthesis of procyanidins and observations on the metabolism of cyanidin in plants

摘要: Evidence based on the results of feeding experiments with labelled (3H,14C) cinnamic acids is presented to show that various procyanidin dimers are biosynthesised from two metabolically distinct units. One flavan-3-ol [(+)-catechin (10) or (–)-epicatechin (9)] and other C-4 carbocation (7) (8). It postulated carbocations derived by protonation flav-3-en-3-ol (6) intermediates in reduction flavan-3-ols (9) (10). The relationship biosynthesis anthocyanidin formation certain plants briefly discussed.