Acute Antidepressant Activity Investigation of Selected African Medicinal Plants in Mice: A Preliminary Study

Abstract

The therapeutic gap arising from high global incidence of depressive disorders and the efficacy and toxicity shortcomings of existing antidepressant drugs indicate a need to further search the plant kingdom with the goal of discovering novel antidepressant pharmacotherapeutic agents. Crude 50% ethanol Terminalia catappa (CETC), Tapinanthus dodoneifolius (CETD) and Bryophyllum pinnatum (CEBP) leaf extracts were investigated for their acute antidepressant activity on the forced swim (FST) and tail suspension (TST) tests. Groups of mice (n = 6) were each exposed to the tests 1 hour following oral administration of distilled water (10 ml/kg), extracts (125, 250 and 500 mg/kg body weight) and fluoxetine (20 mg/kg), using the mean immobility time as endpoint. Qualitative phytochemical analysis of these crude extracts indicated the presence of alkaloids, cardiac glycosides, saponins, phenolic compounds, tannins, steroids, carbohydrates, flavonoids, terpenoids and anthraquinones. Compared to distilled water treatments (FST, 84.16 ±3.92; TST, 82.85 ±5.84), CETC (FST, 84.17 ±4.44, 71.67 ±1.89, & 44.31 ±8.23*; TST, 79.03 ±2.62, 74.10 ±3.11, & 52.57 ±6.00*) and CEBP (FST, 77.02 ±2.70, 66.11 ±4.42 & 49.99 ±4.20*; TST, 69.51 ±7.24, 49.73 ±11.85* & 46.39 ±5.68**) treatments caused dose-dependent and significant (P < 0.05) reductions in the mean immobility times on both paradigms while CETD caused dose-dependent and significant (P < 0.05) reductions of this parameter only on the TST. Overall, acute antidepressant activities at the highest dose level (500 mg/kg) of all extracts approximated that of the standard antidepressant fluoxetine (20 mg/kg). The findings of this study are a justification for the widespread ethnomedicinal uses of extracts of these plants. There is a need to further characterize their antidepressant and other neuropharmacological effects. 1.