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Structural characteristics of flavanols or flavan-3-ols. Catechins comprise a subfamily of flavonoids, which structurally do not possess a double bond between the C2 and C3 carbons or a carbonyl group on the C ring. Due to these characteristics and hydroxylation on the C3, the configuration of four diastereoisomers results: the trans (2S, 3R) and (2R, 3S) isomers, called catechins, and the cis (2S, 3S) and (2R, 3R) isomers, called epicatechins.
