Produces the terminal flavan-3-ol monomers required for the formation of proanthocyanidins or condensed tannins in leaves and flowers, as well as in the skin and seeds of developing berries (By similarity). Behaves as a reductase and as a C-3 epimerase (By similarity). Catalyzes the double reduction of anthocyanidins, producing a mixture of (2S,3S)- and (2S,3R)-flavan-3-ols (By similarity). The enzyme catalyzes sequential hydride transfers to C-2 and C-4, respectively and epimerization at C-3 is achieved by tautomerization that occurs between the two hydride transfers (By similarity). Converts cyanidin, pelargonidin and delphinidin into catechin and epicatechin, afzelechin and epiafzelechin, and gallocatechin and epigallocatechin respectively (PubMed:16806954). a (2S,3R)-flavan-3-ol + 2 NADP(+) = an anthocyanidin with a 3-hydroxy group + 2 H(+) + 2 NADPH a (2S,3S)-flavan-3-ol + 2 NADP(+) = an anthocyanidin with a 3-hydroxy group + 2 H(+) + 2 NADPH Optimum pH is 5.5. Optimum temperature is 45 degrees Celsius. Secondary metabolite biosynthesis; flavonoid biosynthesis. Expressed in leaves and grape berries. Hyperbolic binding of NADPH and NADP(+) to the free enzyme, with a single binding site each. The most likely enzymatic mechanism is sequential ordered Bi-Uni-Uni-Bi, with NADPH binding first and NADP(+) released last. This enzyme is strictly pro-S stereospecific and the reaction mechanism involves two hydride transfers from two distinct NADPH molecules. Belongs to the NAD(P)-dependent epimerase/dehydratase family. Dihydroflavonol-4-reductase subfamily.