Oxidoreductase that catalyzes the last step in the biosynthesis of the benzylisoquinoline alkaloid noscapine (PubMed:27378283, PubMed:29610307). Converts narcotine hemiacetal to noscapine (PubMed:27378283). NAD(+) + narcotine hemiacetal = H(+) + NADH + noscapine Alkaloid biosynthesis. Belongs to the NAD(P)-dependent epimerase/dehydratase family.