Catalyzes the reduction of the double bond of an array of alpha,beta-unsaturated aldehydes and ketones. It also reduces the nitro group of nitroester and nitroaromatic compounds. It could have a role in detoxification processes. A + H(+) + NADPH = AH2 + NADP(+) Homotetramer. Belongs to the NADH:flavin oxidoreductase/NADH oxidase family. NamA subfamily.