Screening of the Antidepressant-like Activity of Two Hypericum Species Found in Ethiopia
The widespread use of Hypericum perforatum for the treatment of mild to moderate depression has prompted screening of the antidepressant-like effect of other species of the genus. The present study was designed to assess the antidepressant-like activity of the 80% methanol extract of Hypericum quartinianum and Hypericum revolutum in behavioral despair model. Eighty percent methanol extract of H. quartinianum and H. revolutum was investigated using learned helplessness models of depression such as tail suspension test (TST), forced swimming tests (FST) and avoidance tests. In addition, locomotor activity was investigated with open field test (OFT). Mice (for TST, avoidance test and OFT) and rats (for FST) were randomly assigned into different groups and treated with distilled water (control), imipramine 64 mg/kg (standard) and extract (200 mg/kg and 400 mg/kg). At 200 and 400 mg/kg, H. revolutum was effective in reducing immobility time in the TST (43.84%, p<0.01 and 49.08%, p<0.01, respectively) and FST (33.7%, p<0.05 and 38.4%, p<0.01, respectively). Similarly, H. quartinianum also showed anti-immobilty effect at 200 (30.67%, p<0.01) and 400 mg/kg (41.19%, p<0.01) in TST. However, only the larger dose produced significant anti-immobility effect in FST (35.3%, p<0.05). Moreover, both extracts at the doses used significantly decreased the escape failure (p<0.01) and increased the intertrial crossing (p<0.05 and p<0.01) during the resting periods in the avoidance task in a shuttle box. In OFT, the tested crude extracts did not significantly alter locomotor activity, suggesting that it is very unlikely that the observed antidepressant effects are false positives. These observations together provide evidence that the 80% methanolic extract of leaves of H. quartinianum and H. revolutum display antidepressant-like actions in established models of behavioral despair without affecting locomotion.
Keywords: Hypericum quartinianum, Hypericum revolutum, depression, antidepressant-like activity