Antinociceptive activity of n-butanol fraction from MeOH extracts of Paederia scandens in mice

The n-butanol fraction of the MeOH extract from Paederia scandens was evaluated for antinociceptive activity in mice using chemical and thermal models of nociception. The n-butanol fraction, given orally at doses of 150, 300 and 600 mg/kg produced significant inhibition of chemical nociception induced by intraperitoneal acetic acid and subplantar formalin or capsaicin injections, and of thermal nociception in the tail-flick test and in the hot plate test. More significant inhibition of nociception was observed at a dose of 600 mg/kg. In the pentobarbital sodium-induced sleeping time test and the open-field test, the n-butanol fraction neither significantly enhanced pentobarbital sodium-induced sleeping time nor impaired motor performance, indicating that the observed anti-nociception was unlikely to be due to sedation or motor abnormality. Moreover, the n-butanol fraction-induced anti-nociception in both the capsaicin and formalin tests was insensitive to naloxone or glibenclamide but was significantly antagonized by nimodipine. These results suggest that the n-butanol fraction produced anti-nociception possibly related to nimodipine-sensitive L-type Ca2+ channels, which merits further studies regarding the precise site and mechanism of action. Furthermore, four iridoid glycosides isolated from the n-butanol fraction might be related to its antinociceptive action fraction. Therefore, the effect on analgesic activity of each chemical compound in large quantity might well be considered in a further study.