Background and objectives: Hypericum (H.) perforatum, popularly called St. John's Wort has been used traditionally for the treatment of anxiety, depression and as a nerve tonic. Large amount of clinical and animal experimental data demonstrate that H. perforatum acts by biochemical mechanisms similar to the tricyclic antidepressants or serotonin reuptake inhibitors. However, its efficacy in comparison to standard antidepressant drugs is not well studied. The present study evaluated H. perfortum extract in animal models of depression compared to clinically used antidepressants.
Materials and methods: The effects of standardized extract of H. perforatum was compared with standard antidepressants using animal models of depression such as forced swim test (FST), yohimbine induced lethality test, pnetylenetetrazole (PTZ) induced convulsion and locomotor activity tests. Different doses of the plant extract and standard drugs were administered to rats or mice intraperitoneally (i.p).
Results: In the FST, H. perforatum extract (30-90 mg/kg i.p.) caused a dose dependent reduction in immobility time in rats with maximal effect being 53% at 90 mg/kg. This effect was reversed at higher doses (100 mg/kg) showing a U-shaped dose response curve. Fluoxetine and imipramine (30-70 mg/kg i.p.) produced similar reduction in the immobility time in rats. Venlafaxine exhibited weak antidepressant effect. H. perforatum extract (30-100 mg/kg i.p.), dothiepin (10-50 mg/kg i.p.), fluoxetine (30-60 mg/kg i.p.) and venlafaxine (20-40 mg/kg i.p.) potentiated yohimbine induced lethality. PTZ induced toxicity was also enhanced with these agents. In the locomotor activity test H. perforatum decreased the locomotor counts of mice similar to standard antidepressants.
Conclusions: H. perforatum has antidepressant properties similar to standard antidepressants. The antidepressant profile of H. perforatum is closely related to the selective serotonin reuptake inhibitors class of antidepressants.