Inhibition of monoamine oxidase by higenamine

Higenamine, a benzylisoquinoline alkaloid, has beta-receptor stimulatory or alpha-receptor blocking activities in isolated rat atria and aorta. It also decreases the dopamine content of PC 12 cells. In this study, we investigated whether higenamine has an effect on dopamine catabolism using mouse brain monoamine oxidase (MAO). Higenamine showed a mild inhibition of MAO (41.6% inhibition at 150 mu M). The IC50 value of higenamine was 159.0 mu M Higenamine non-competitively inhibited MAO activity with kynuramine as substrate and the K-i value was 187.7 mu M. These results suggest that higenamine may partially contribute to the regulation of catecholamine content of these cells. Med Sci Res 27:71-72 (C) 1999 Lippincott Williams & Wilkins.