Evaluation of the antidepressant-like activity of solvent fractions of the aerial parts of Hypericum revolutum (Hypericaceae) in rodent models

Abstract

Various species of the genus Hypericum have been traditionally used for different purposes. A previous study showed that 80% methanol extract of Hypericum revolutum was active in animal model of depression. The present study was performed on solvent fractions of the crude extract as part of the effort to develop a candidate drug from the plant. The fractions (chloroform, butanol and aqueous) were prepared using liquid-liquid extraction from 80% methanol extract. Antidepressant-like activity of the fractions was investigated at various doses (100, 200 and 400 mg/kg) using a host of paradigms, including forced swim test (FST), tail suspension test (TST) and open field test (OFT). Moreover, preliminary phytochemical screening and finger printing using thin layer chromatography were undertaken. Promising antidepressant-like activity was detected with 200 mg/kg and 400 mg/kg (p < 0.05) of the butanol and chloroform fractions in the FST and TST. The doses did not, however, produce significant effect on spontaneous motor activity when assessed in OFT. The aqueous fraction was devoid any activity. The findings indicate that the higher doses of chloroform and butanol fractions possess antidepressant-like activity as evidenced by significant decrease in the duration of immobility in the two paradigms. These effects of fractions were displayed without significant effect on locomotor activity, suggesting that the antidepressant-like activity observed is not caused by a non-specific motor stimulation. In addition, the preliminary phytochemical screening indicated that the fractions contained different secondary metabolites previously reported to have antidepressant-like effects.

Keywords: Hypericum revolutum, anti-depressant activity, solvent fractions, forced swimming test, tail suspension test