Evaluation of Antidepressant-Like Activity of Solvent Partitioned Fractions of Olax subscorpioidea Oliv. (Olacaceae) Leaf Extract in Rodents

Abstract

Olax subscorpioidea is a medicinal plant with a long history in traditional medicine for the treatment of mental illness in Nigeria. The current study investigated antidepressant-like activity of solvent partitioned fractions. The crude extract was partitioned in increasing order of polarity to yield ethyl-acetate fraction (EAF), butanol fraction (BF) and aqueous fraction (AF). They were evaluated for antidepressant activity at doses of 5-20 mg/kg in mice using the forced swim test, tail suspension and reserpine tests. The BF, the most active was adsorbed on silica gel and subjected to vacuum liquid chromatography to yields several fractions which were subsequently pooled into five sub-fractions, F1-F5 and screened for antidepressant action. F1 being the most active one was subjected to column chromatography with n-hexane, dichloromethane and ethylacetate. The yields of twenty-six fractions were pooled into four fractions f1-f4 and were screened with the FST and TST only. The EAF, BF, F1, f1, f2, f3 and f4 fractions significantly (P<0.05) reduced immobility in the FST and TST without locomotor effect. The BF and F1 significantly (P<0.05) reversed reserpine-induced hypothermia. From the data obtained, it was observed that among all the fractions, BF, F1, f1, f2, f3 and f4 possess prominent antidepressant-like and antiimmobility effects in both FST and TST. This activity increases as the extract and fractions were further separated. This shows that the plant may have important phytochemicals with great potential for the development of a new antidepressant, thus justifying the traditional use of the plant in mental illness.