Inhibitory effects of protoberberine alkaloids from the roots of Coptis japonica on catecholamine biosynthesis in PC12 cells.

The effects of protoberberine alkaloids from Coptis japonica Makino (COPT) on catecholamine content and tyrosine hydroxylase (TH) activity in PC12 cells were investigated. The butanol (BuOH) fraction from COPT at a concentration of 40 micrograms/ml medium inhibited catecholamine biosynthesis. The BuOH fraction was further fractionated into separate bioactive fractions (Fr. I-IV) by silica gel column chromatography, and Fr. II and III, which contain protoberberine alkaloids such as berberine and palmatine, were isolated. Fr. III at 40 micrograms/ml medium showed 77% inhibition on dopamine content in PC12 cells (IC50; 19.5 micrograms/ml medium). TH activity was reduced by the treatment of Fr. III. Berberine and palmatine also showed an inhibitory activity on dopamine biosynthesis in PC12 cells. The IC50 values of berberine and palmatine were 9.5 and 7.7 micrograms/ml medium, respectively. This suggests that the protoberberine alkaloids from COPT have an inhibitory effect on catecholamine biosynthesis by reducing TH activity in PC12 cells.