ABSTRACT
Monoamine oxidase inhibitors (MAOI) have been widely used as antidepressants. Recently, there has been renewed interest in MAO inhibitors. The activity-guided fractionation of extracts from Angelica keiskei Koidzumi (A. keiskei K.) led to the isolation of two prenylated chalcones, xanthoangelol and 4-hydroxyderricin and a flavonoid, cynaroside. These three isolated compounds are the major active ingredients of A. keiskei K. to inhibit the MAOs and DBH activities. Xanthoangelol is a nonselective MAO inhibitor, and a potent dopamine beta-hydroxylase (DBH) inhibitor. IC50 values of xanthoangelol to MAO-A and MAO-B were calculated to be 43.4 microM, and 43.9 microM. These values were very similar to iproniazid, which is a nonselective MAO inhibitor used as a drug against depression. The IC50 values of iproniazid were 37 microM, and 42.5 microM in our parallel examination. Moreover, IC50 value of xanthoangelol to DBH was calculated 0.52 microM. 4-Hydroxyderricin is a potent selective MAO-B inhibitor and also mildly inhibits DBH activity. The IC50 value of 4-hydroxyderricin to MAO-B was calculated to be 3.43 microM and this value was higher than that of deprenyl (0.046 microM) used as a positive control for selective MAO-B inhibitor in our test. Cynaroside is a most potent DBH inhibitor. The IC50 value of cynaroside to DBH was calculated at 0.0410 microM. Results of this study suggest that the two prenylated chalcones, xanthoangelol and 4-hydroxyderricin isolated from A. keiskei K., are expected for potent candidates for development of combined antidepressant drug. A. keiskei K. will be an excellent new bio-functional food material that has the combined antidepressant effect.