Biochemical activities of extracts from Hypericum perforatum L. - 1st Communication: Inhibition of dopamine-beta-hydroxylase

Extracts From the herb "St. John's wort" (Hypericum perforatum L.) are used for the treatment of mental depression, nervousness, sleeplessness and for their wound healing, diuretic and antirheumatic properties. As one biochem ical mechanism for depression lack of catecholamine neurotransmitters has b een discussed. The results of this investigation show that alcoholic extrac ts from Hypericum perforatum L. on the basis of total hypericin content inh ibit dopamine-beta-hydroxylase with an IC50 of 0.1 mu mol/l: pure commercia l hypericin inhibits with an IC50 of 21 mu mol/l. Enzymes involved in the s ynthesis of dopamine from tyrosine, namely tyrosinase and tyrosine decarbox ylase, are not influenced by hypericin at concentrations from up to 10 mu m ol/l.