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(A) Chemical structure of a proanthocyanidin consisting of the catechin and epicatechin polymeric units, where “n” is any number that makes up the polymer; (B) Generic structure of a flavonoid. Kaempferol, R1 = H, R2 = H; quercetin, R1 = OH, R2 = H; myricetin, R1 = OH, R2 = OH.
