RESUMEN
Lichens and their secondary metabolites have attracted the interest of many researchers. Some species have been shown to contain substances with remarkable biologic activity, as antimicrobial, mainly against Gram positive bacteria; antineoplasic acting on solid and ascetic tumors, or in culture cells; antiviral; hypotensive; and spasmolytic effects. The aim of this study was to isolate and characterize atranorin, one of the major constituents which presents in Cladina kalbii (DES ABB.) AHTI., and analyze its antinociceptive effect. The antinociceptive activity was verified in acetic acid-induced writhing test and formalin test with mice. In this work it was observed that atranorin was effective in significant reducing (p<0.05) abdominal writhing at doses of 200 and 400 mg/kg (p.o.) by 52.6 and 61.3%, respectively, when compared to control group (vehicle). The formalin test showed in 200 and 400 mg/kg (p.o.) that atranorin injection was able to inhibit the inflammatory processes (second phase) dose dependently.