Evidence for involvement of the monoaminergic system in antidepressant-like activity of an ethanol extract of Boerhaavia diffusa and its isolated constituent, punarnavine, in mice.

Context: Boerhaavia diffusa Linn. (Nyctaginaceae) roots possess potent antioxidant, antistress, and anticonvulsant activities. It is used as a medicinal plant in Ayurvedic and natural herbal medicines.

Objective: To evaluate the effect of Boerhaavia diffusa root ethanol extract and its active constituent, punarnavine, on depression in Swiss albino mice.

Materials And Methods: Ethanol extract (50, 100, and 200 mg/kg, p.o.) and punarnavine (20 and 40 mg/kg, p.o.) were separately administered to 22 and 17 groups of mice, respectively, for 14 successive days followed by testing in the tail suspension and forced swim tests (FST). About 2% w/v gum acacia and double distilled water were used as controls for the extract and punarnavine, respectively.

Results: Antidepressant-like effect of the lowest dose (50 mg/kg) of the extract and lower dose (20 mg/kg) of punarnavine were found to be comparable to fluoxetine. The ED50 value of the ethanol extract was 26.30 mg/kg (FST) and 33.11 mg/kg (tail suspension test); and of punarnavine was 15.14 mg/kg (FST) and 17.38 mg/kg (tail suspension test). The drugs did not show any significant effect on locomotor activities of mice. Prazosin (α1-adrenoceptor antagonist), sulpiride (selective D2-receptor antagonist), para-chlorophenylalanine) (p-CPA) (tryptophan hydroxylase inhibitor), and baclofen (GABAB agonist) significantly attenuated the extract and punarnavine induced-antidepressant-like effect in the tail suspension test. The extract and punarnavine also significantly reduced mouse brain monoamine oxidase (MAO)-A levels, but there was no significant effect on plasma corticosterone levels.

Conclusion: Ethanol extract of Boerhaavia diffusa and punarnavine produced an antidepressant-like effect in mice probably through interaction with monoaminergic and GABAergic systems.