Anti-inflammatory and analgesic activities of mature fresh leaves of Vitex negundo

Abstract

This study confirmed the oral anti-inflammatory, analgesic and antihistamine properties of mature fresh leaves (MFL) of Vitex negundo L. (Verbenaceae) claimed in the Ayurveda medicine by orally treating a water extract of the leaves to rats. The early phase (2 h) of carrageenan-induced rat paw oedema was significantly ( P<0.01) suppressed in an inversely does-dependent ( r 2=1, P<0.01) manner by MFL. The EC 50 was 2 g/kg of MFL. In the formaldehyde-induced rat paw oedema test, the 2.5 and 5 g/kg leaves significantly ( P<0.05) suppressed the inflammation on days 4–6 of the test. In the hot plate test, 2.5 and 5 g/kg of MFL showed a significant ( P<0.05) and directly dose-dependent analgesic activity at 1 h of treatment while the activity was absent in the tail flick test in rats. The EC 50 for the analgesic activity was 4.1 g/kg. In the formalin test, 1.25, 2.5 and 5 g/kg of MFL significantly ( P<0.05) suppressed the pain in both the phases of the test like aspirin. The leaves showed an inversely dose-dependent in vivo antihistamine and in vitro prostaglandin (PG) synthesis inhibition, membrane stabilising and antioxidant activities. Naloxone did not abolish the analgesic activity in the hot plate test. A 5 g/kg of MFL did not impair muscle strength and co-ordination and did not induce sedation. The treatment of 5 g/kg of MFL did not show signs of acute toxicity or stress. Fourteen-day oral treatment of 5 g/kg of MFL significantly increased the serum activity of AST. Flowering of the tree did not abolish the analgesic and anti-inflammatory activities of the leaves. These observations revealed that the fresh leaves of Vitex negundo have anti-inflammatory and pain suppressing activities possibly mediated via PG synthesis inhibition, antihistamine, membrane stabilising and antioxidant activities. The antihistamine activity can produce the anti-itching effect claimed in Ayurveda medicine.