The aim of this study was to evaluate the
analgesic effect of the methanolic extract from callus culture of Phyllanthus tenellus, P. corcovadensis and P. niruri in several models of
pain in mice. The extracts (medium containing
2,4-dichlorophenoxyacetic acid) of P. corcovadensis, P. niruri and P. tenellus (3-90 mg kg-1, i.p.) caused graded inhibition of abdominal constrictions induced by
acetic acid (0.6%), with ID50 (i.e. dose that reduced response of control by 50%) values of about 30, 19 and > 30 mg kg-1, respectively. The extract of callus of Phyllanthus obtained in
indole-3-butyric acid and
indole-3-acetic acid media (3-90 mg kg-1, i.p.) caused a similar
analgesic effect. In the
formalin test, the extract of P. tenellus obtained in
indole butyric acid medium (3-100 mg kg-1, i.p.) inhibited only the second phase of
formalin-induced
pain with an ID50 value of about 100 mg kg-1. Both the
indole acetic acid and
indole butyric acid methanolic extracts of P. tenellus and P. corcovadensis (10-100 mg kg-1, i.p.) dose-dependently inhibited both phases of
formalin-induced
pain (ID50 values for the second phase were approx. 100 and 52 mg kg-1, respectively). However, the extract of callus from Phyllanthus failed to affect
formalin-induced paw oedema, as well as the response to radiant heat in the tail-flick test. In addition, the
analgesic effect of
morphine, but not the
analgesic effects caused by Phyllanthus callus extract, was fully antagonized by
naloxone.(ABSTRACT TRUNCATED AT 250 WORDS)