The genus, Calliandra is popularly used for renal pain, cystitis, prostate inflammation, fever and toothache. This study aimed at investigating the antinociceptive activity of methanolic crude extract (MCE) of Calliandra umbellifera, regarding chemical (acetic acid, formalin and glutamate tests) of nociception (in vivo) and the methanolic extract and hidrobutanolic phase (HBF) antioxidant activity by the 2,2-diphenyl-1-picril-hidrazil (DPPH) method, besides determination of the content of phenolic compounds and flavonoids (in vitro). The pre-treatment with the MCE (100, 200 and 300 mg/kg, p.o) was able to reduce the number of abdominal contortions (p<0.01 or p<0.001), the licking times in the formalin (p<0.001) and the glutamate tests (p<0.01), respectively. In the antioxidant assay, the extract showed optimum EC 50 and higher flavonoid content as compared to the hydrobutanolic fraction; however, the content of the obtained phenolic compounds were higher in HBF as compared to MCE. The experimental data showed that C. umbellifera has an antinociceptive activity, a good antioxidant activity and high levels of phenolic compounds, which confirms the popular use of Calliandra, contributing to the scientific knowledge of the species.

Hydantoins are often reported as potent anticonvulsant drugs; however, recent studies have highlighted their antinociceptive potential. Based on these reports, this study investigated the antinociceptive and anti-inflammatory activities of the hydantoin derivative 5-(4-isopropylphenyl)-3phenyl-imidazolidine-2,4-dione (IM-7) using animal models. Treated mice submitted to the acetic acidinduced writhing test showed increase (p<0.01 or p<0.001) in the latency to the first writhing and reduction in the number of abdominal writhing (p<0.001). Furthermore, all doses reduced the nociceptive response in the first (p<0.05 or p<0.001) and second (p<0.001) phases of the formalin test. This effect was inhibited by pretreatment with the antagonists naloxone, sulpiride and caffeine. Additionally, IM-7 (75, 150 and 300 mg/kg, i.p.) reduced (p<0.05 or p<0.001) the glutamate-induced nociceptive response. Carrageenan-induced paw edema was strongly reduced following treatment with all doses of IM-7 (p<0.05, p<0.01 or p<0.001), and so were leukocyte migration and levels of interleukin-1β (300 mg/kg: p<0.001) and tumor necrosis factor-α (300 mg/kg: p<0.01) in carrageenan-induced peritonitis. Therefore, IM-7 decreased the nociceptive response via a mechanism involving the opioid, dopaminergic, and adenosinergic receptors. Its anti-inflammatory action also contributed by decreasing the release of pro-inflammatory cytokines.