Antinociceptive effect of crude extract, fractions and three alkaloids obtained from fruits of Piper tuberculatum.

This study investigated the possible antinociceptive effect of the crude extract, fractions and pure compounds (three alkaloids) obtained from fruits of Piper tuberculatum JACQ. (Piperaceae) in acetic acid-induced visceral pain in mice. Oral administration of crude extract and fractions (CH(2)Cl(2), EtOAc, methanol and hexane) (3-300 mg kg(-1)) caused a dose-related and significant inhibition of the acetic acid-induced visceral nociceptive response. The crude extract, dichloromethane (CH(2)Cl(2)) and ethyl acetate (EtOAc) fractions were more potent than methanol and hexane fractions. The isolated alkaloids dihydro-piplartine, piplartine and 3,4,5-trimethoxydihydrocinnamic acid (0.0001-30 mg kg(-1)) exhibited significant and dose-related antinociceptive effects against acetic acid-induced visceral pain. The results show, for the first time, that crude extract, fractions and pure compounds obtained from P. tuberculatum produce marked antinociception against the acetic acid-induced visceral nociceptive response, supporting the ethnomedical use of P. tuberculatum.