Monoamine oxidase inhibitors from a fungus, Emericella navahoensis.

Norsolorinic acid, averufin and 6, 7, 8-trihydroxy-3-methylisocoumarin were isolated from Emericella navahoensis as metabolites having monoamine oxidase (MAO)-inhibitory action. Norsolorinic acid inhibited MAO in mouse liver non-competitively when kynuramine was used as a substrate, and its IC50 was 0.3 μM. The inhibition constants (Ki) for MAO-A and -B in mouse liver were 0.24 and 0.68 μM, respectively. On the other hand, Ki values for MAO-A and -B in mouse brain were 2.9 and 0.32 μM, respectively. Inhibitory potencies towards MAO of some anthrquinone derivatives were also examined.