RESUMEN
The present study describes the analgesic activity of extracts and some fractions obtained from Erythrina crista-galli leaves in different in vivo analgesic models, using mice as experimental animals. The results showed that extract E(2) was the most active, inhibiting 48% of the abdominal constrictions when evaluated against the writhing test at 10 mg kg(-1), intraperitoneal. It also caused dose-dependent inhibition in the same model, with a calculated ID(50) value and respective confidence interval of 10 (9-14) mg kg(-1), and was more potent than reference drugs. Administered orally, E(2) caused potent antinociceptive action, with a calculated ID(50) value of 35 (26-47) mg kg(-1). The fractions F(1) and F(2) obtained from E(2) were evaluated against the writhing test at 10 mg kg(-1), causing inhibitions of 41 and 88%, respectively. The most active fraction, F(2), presented ID(50) calculated value of 3 (2-4) mg kg(-1), being about 7-fold more active than the reference drugs (acetyl salicylic acid and acetaminophen). In the formalin test, F(2) inhibited both phases of pain (44%, first phase; 58%, second phase). However, in contrast to the results observed for E(2), it was not active against the hot-plate test. The phytochemical results showed that at least four main components are present in F(2), which show a positive reaction of terpenes with TLC spray reagents.