Evaluation of peripheral and central analgesic activity of ethanolic extract of Clerodendrum infortunatum Linn. in experimental animals

Background: Clerodendrum infortunatum Linn. (Verbenaceae) is an important and widely used medicinal plant. Though variously used in Ayurveda, Unani, and Homeopathy system of medicine in the case of ailments such as diarrhoea, skin disorders, venereal and scrofulous complaints, wounds, post-natal complications, as anti-helminthic, and external applications on tumors, the plant needs thorough investigation for its specific medicinal activity. This study evaluates both the central and peripheral analgesic effect of the ethanolic extract of the leaves of C. infortunatum Linn. (EECI) in the experimental animals.Methods: Acute toxicity test was done following the Organization of Economic Co-operation and Development guidelines. EECI (100 mg/kg, 200 mg/kg, and 400 mg/kg body weight [b.w.] p.o) was evaluated for central analgesic activity by the tail flick method and peripheral analgesic activity by the acetic acid (0.7%) induced writhing test, respectively. Using aspirin (300 mg/kg b.w. and 100 mg/kg b.w.) as the standard drug.Results: EECI significantly decreased the number of writhing in writhing test at all the doses (p<0.01) and increased the reaction time in tail-flick method (p<0.01) at all the doses. EECI in the dosage of 400 mg/kg b.w. produced effects which was comparable with that of the standard drug aspirin (p<0.001) in writhing test (p<0.001) and tail flick method (p<0.001).Conclusion: The study showed significant central and peripheral analgesic activity of EECI which may be attributed to the inhibition of prostaglandin synthesis, phospholipase A2, and tumor necrosis factor alpha. C. infortunatum Linn. as a commercial source of analgesic drug should be subjected to further research