Phytochemistry of proanthocyanidins

Procyanidin A from Aesculus hippocastanum differs from the B type procyanidin in that it is difficultly soluble in water, gives a higher yield of cyanidin when heated in butanolic HCl and the production of cyanidin continues beyond the 2 hr period sufficient for maximum production in the case of B type procyanidin. Anthocyanidin production and tannic acid equivalent (TAE) of extracts of species in which A and D type procyanidins have been reported to occur have been studied. Evidence of their presence was also found in Ribes laurifolium. Preparations of prodelphinidin from leaves of red currant and sainfoin had approximately twice the anthocyanidin production and the astringency of procyanidin B. Sources especially rich in prodelphinidin were a number of Ribes spp., Salix cinerea and Platanus acerifolia, from all of which the tannin was easily extracted. Some other species such as Pilea cadieri, although rich in prodelphinidin, are not suitable as sources because of the inextractability of the tannin.