Analgesic Effect of Hexane Fraction from Roots of Lonchocarpus sericeus

Abstract

Lonchocarpus sericeus (Poir.) Kunth is a plant belonging to the Fabaceae family and commonly found in Northeast Brazil. The objective of the present work was to study the analgesic effect of the hexane fraction from roots of L. sericeus (HFLS) which contains lonchocarpin and derricin as its main constituents. Results showed a potent antinociceptive effect of HFLS in the tests of acetic acid-induced abdominal contractions and formalin in mice. In the acetic acid-induced writhing test, HFLS produced inhibitions up to 65% when administered orally or subcutaneously. In the same test, the co-administration of HFLS (200 mg/kg, p.o.) and thalidomide (5 mg/kg, p.o.), a TNF-a inhibitor, showed a potentiation of the antinociceptive effect of HFLS. However, in the abdominal contractions induced by acetylcholine, HFLS did not produce any effect. In the formalin test, HFLS (100, 200 and 400 mg/kg, p.o.) caused 45, 59 and 70% inhibitions, respectively, of the 2nd phase of the test. Intraperitoneally HFLS (100 and 200 mg/kg) presented a dose-dependent effect predominantly on the 2nd phase of the response with inhibitions of the licking time of 58 and 93% respectively. The inhibitory effect of HFLS was not reversed by naloxone, suggesting that the opioid system is not involved in antinociception. Although l-arginine blocked the antinociceptive activity of L-NAME, it was not able to antagonize HFLS antinociception, indicating that nitric oxide system does not play a role in the observed effect.