Abstract:
1,2-Dihydrosantonin is the first stable product in the degradative pathway of alpha-santonin byPseudomonas cichorii S. Its formation is catalyzed by an oxidoreductase, which is NADH or NADPH dependent and has an apparent Km value of 66.66 mu M for santonin and 44.33 mu M for NADH. The enzyme activity is stable at pH 6.0, 7.0, and 8.0, and is not affected by EDTA and divalent metal ions. It is postulated that the enzymic reduction of santonin occurs via formation of a transient zwitterionic intermediate, which undergoes nonenzymatic 1,4-sigmatropic rearrangement to yield lumisantonin during the solvent extraction process. Lumisantonin is, thus, not a true metabolic intermediate but an artifact.
