In the Amaryllidaceae alkaloids biosynthesic pathway, catalyzes the conversion of noroxomaritidine to oxomaritidine, a precursor of haemanthamine- and crinamine-type alkaloids, promising anticancer agents (PubMed:27252378). Can also, to some extent, catalyze the condensation of 3,4-dihydroxybenzaldehyde (3,4-DHBA) and tyramine to produce norbelladine, and of isovanillin and tyramine to produce 4'-O-methylnorbelladine (PubMed:27252378). (10bR,4aS)-noroxomaritidine + H(+) + NADPH = (10bR,4aS)-oxomaritidine + NADP(+) (10bS,4aR)-noroxomaritidine + H(+) + NADPH = (10bS,4aR)-oxomaritidine + NADP(+) Optimum pH is 6. Optimum temperature is 35 degrees Celsius. Alkaloid biosynthesis. Belongs to the short-chain dehydrogenases/reductases (SDR) family. SDR65C subfamily.