Abstract
The present study deals with the chemical composition and antinociceptive effects of Plinia edulis fruit peels, analyzed by writhing, formalin, glutamate and capsaicin tests and comparison with two reference analgesic drugs, acetylsalicylic acid and acetaminophen. Phytochemical analyses of the nonpolar fraction (dichloromethane) obtained from the peels of P. edulis fruits revealed the presence of two triterpenes, maslinic acid and ursolic acid. The methanol extract of P. edulis peels showed a pronounced antinociceptive activity in the writhing test, with inhibition of 91.3% at 10 mg/kg, and its dichloromethane and ethyl acetate fractions presented inhibition of 68.3% and 51.5%, respectively. Maslinic acid showed a dose-dependent effect with inhibition of 60.8% at a dose of 10 mg/kg and ID50 value of 3.31 (2.75 to 4.0) mg/kg. The dichloromethane fraction, evaluated in the formalin-induced pain model at a dose of 10 mg/kg, showed a significant effect on both phases of pain. Maslinic acid was evaluated at different doses (1, 3 and 6 mg/kg) and presented a dose-dependent profile in both phases of pain, being more effective than the reference drug (acetaminophen), which was evaluated at 10 mg/kg. The dichloromethane fraction also inhibited the pain induced by glutamate and capsaicin by around 54% and 44%, respectively, whereas maslinic acid was more effective against glutamate, with 62.5% inhibition at 6 mg/kg, and 32% inhibition against capsaicin-induced pain. The results demonstrated that the pronounced antinociceptive effect presented by P. edulis fruits peels is related, at least in part, to the presence of the triterpenes evidenced in this study.