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Common representation of condensed tannin structures. Left structure: PC = procyanidin; catechin (trans isomer) or epicatechin (cis isomer). PD = Prodelphinidin; gallocatechin (trans isomer) or epigallocatechin (cis isomer). In addition, hydroxyl groups, particularly on the C-3 hydroxyl, may be esterified with a galloyl (G) group (structure on the right). Carbons 2, 3, and 4 of the C ring, 2′ and 6′ of the B ring, 6 and 8 of the A ring, and 2” and 6” of the D ring are labeled.
