Antinociceptive properties of extracts of new species of plants of the genus Phyllanthus (Euphorbiaceae)

The hydroalcoholic extract (HE) of the four new species of Phyllanthus, giv en intraperitoneally, produced significant inhibition of acetic acid-induce d abdominal constrictions, with mean ID50 values of 0.3, 1.8, 7.4 and 26.5 mg/kg for Phyllanthus amarus, Phyllanthus orbiculatus, Phyllanthus fraternu s and Phyllanthus stipulatus, respectively. In the formalin test, the four species of Phyllanthus, also produced graded inhibition against both phases of formalin-induced licking, being more active in relation of the late pha se. The HE of the Phyllanthus species elicited significant inhibition of th e capsaicin-induced neurogenic pain, with mean ID50 values of 8.9, 6.7, > 3 0 and similar to 30 mg/kg for P. amarus, P. fraternus, P. stipulatus and P. orbiculatus, respectively. Given orally all HE of the Phyllanthus species were less potent and efficacious than when given by intraperitoneally. Resu lts of the present study extend previous data and indicate that all extract s of Phyllanthus plants so far studied exhibit pronounced antinociception w hen assessed in chemical models of nociception, namely acetic acid-induced writhing, and formalin and capsaicin-induced licking. (C) 2000 Elsevier Sci ence Ireland Ltd. All rights reserved.