Inhibitory Effects of the Stem Bark of Albizia julibrissin on Catecholamine Biosynthesis in PC12 Cells

The methanol extract of Albizzia julibrissin Durazz. (Leguminosae) was successively partitioned into dichloromethane, ethylacetate, butanol (BuOH) and water fractions, and the effects of the each solvent extract on catecholamine biosynthesis in PC12 cells were investigated. Among them, the BuOH fraction $(5{\mu}g/ml\;medium)$ showed 68.8% and 63.6% inhibition on dopamine and norepinephrine content in PC12 cells, respectively. Tyrosine hydroxylase (TH) activity was also reduced markedly by treatment of the BuOH fraction (41.8% inhibition at $5{\mu}g/ml$ in the medium). Each solvent fraction did not show cytotoxicity towards PC12 cells by trypan blue exclusion test. This result suggests that the BuOH fraction has an inhibitory effect on catecholamine biosynthesis by reducing TH activity in PC12 cells.