In enzymology, alpha-santonin 1,2-reductase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are santonin, reduced nicotinamide adenine dinucleotide (NADH), and a proton. Its products are 1,2-dihydrosantonin and oxidised NAD<sup>+</sup>. The enzyme can also use nicotinamide adenine dinucleotide phosphate as an alternative cofactor.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-CH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 1,2-dihydrosantonin:NAD(P)+ 1,2-oxidoreductase.