Screening for the antidepressant activity of some species of Hypericum from South Brazil

The crude methanol extracts of three species of the genus Hypericum (H. brasiliense, H. caprifoliatum and H. myrianthum) native to South Brazil were evaluated for the antidepressant activity according to the forced swimming test, a classical animal model for antidepressant drug screening. Among the species studied, only H. caprifoliatum showed activity. Thus, this plant was fractionated with solvents in increasing polarity (petroleum ether; petroleum ether: chloroform (1:1); chloroform and methanol). The petroleum ether fraction was the only one which demonstrated antidepressant activity at a dose of 270 mg/kg/day (i.p.). The chemical analyses showed that this fraction is rich in phenolic compounds, mainly of the phloroglucinol type.