Bifunctional enzyme involved in the flavonoid metabolism. May use dihydroquercetin, eriodictyol, garbanzol (5-deoxydihydrokaempferol), dihydrofisetin (5-deoxydihydroquercetin), dihydrokaempferol to a low extent (5%), but not naringenin, 5-deoxynaringenin or butin (5-deoxyeriodictyol) as substrate. a (2R,3S,4S)-leucoanthocyanidin + NADP(+) = a (2R,3R)-dihydroflavonol + H(+) + NADPH (2S)-flavan-4-ol + NADP(+) = (2S)-flavanone + H(+) + NADPH Optimum pH is 5.75 with dihydroquercetin as substrate. Belongs to the NAD(P)-dependent epimerase/dehydratase family. Dihydroflavonol-4-reductase subfamily.