Catalyzes the asymmetric reduction of o-substituted aliphatic and aromatic aldehydes and ketones to an S-enantiomer. Reduces ethyl 4-chloro-3-oxobutanoate to ethyl (S)-4-chloro-3-hydroxybutanoate. a primary alcohol + NADP(+) = an aldehyde + H(+) + NADPH Inhibited by quercetin and diphenylhydantoin. Optimum pH is 5.5. Optimum temperature is 40 degrees Celsius. Monomer. Belongs to the NAD(P)-dependent epimerase/dehydratase family. Dihydroflavonol-4-reductase subfamily.