网页2022年5月4日 · 1. Introduction. Procyanidins (PCs), also called proanthocyanidins and condensed tannins, are widely found in flowers, nuts, fruits, bark, and seeds of various plants [1,2].PCs with a degree of polymerization of 2–4 or more are called oligomeric procyanidins (OPCs) and polymeric procyanidins (PPCs), respectively [].In most cases, the flavane-3-alcohol unit is a substituted derivative of ...