Peripheral and central analgesic activity evaluation of ethanolic extract of Vitex Negundo flowers in experimental animals

Background: Vitex negundo Linn (Family: Verbenaceae), locally known as ‘Nirgundi’ an important medicinal plant is a woody, aromatic shrub growing to a small tree. It commonly bears tri- or penta-foliate leaves on quadrangular branches, which give rise to bluish-purple coloured flowers in branched tomentose cymes. It has been claimed to possess analgesic activity apart from many medicinal properties. The aim of the present study was to evaluate both the peripheral and central analgesic activity of ethanolic extract of Vitex negundo flowers (EEVNF) in experimental animals.Methods: Acute toxicity test was done following the Organization of Economic Cooperation and Development guidelines. EEVNF (100mg/kg, 200mg/kg, and 400 mg/kg body weight [b.w.] p.o) was evaluated for peripheral analgesic activity by the acetic acid (0.7%) induced writhing test and central analgesic activity by the tail flick method respectively using aspirin (100mg/kg b.w. and 300mg/kg b.w.) as the standard drug.Results: EEVNF significantly decreased the number of writhing in writhing test at all the doses (p<0.001) and increased the reaction time in tail-flick method (p<0.001) at all the doses when compared to control. EEVNF in the dosage of 400mg/kg b.w. produced analgesic effects which was comparable with that of the standard drug aspirin at dose 100mg/kg b.w in writhing test and produced greater analgesic activity than that of standard drug aspirin at dose 300mg/kg b.w in tail flick method.Conclusions: EEVNF has significant peripheral and central analgesic activity