Behavioural Effects of Pycnocomolides, Novel Phorbol Derivatives Isolated from Pycnocoma cornuta, in Mice

Abstract

As part of evaluation of plants used in traditional medicine practice in Nigeria, Pycnocoma cornuta was identified for phytochemical and pharmacological studies. The novel phorbol ester derivatives, pycnocomolides, isolated from the leaves of the plant, in doses of 0.1-0.2 mg kg−1 intraperitoneally, markedly inhibited d-amphetamine-induced locomotor stimulation in mice. The most potent pycnocomolide reduced d-amphetamine's response to 24% of the control compared with 21% by haloperidol and 63% by phorbol 12-myristate 13-acetate (PMA). The pycnocomolide similarly inhibited apomorphine-induced response by 55%. Both the pycnocomolide and haloperidol, but not PMA, significantly inhibited spontaneous activities of the animals. The effect of the pycnocomolide was not significantly different from that of haloperidol. We conclude that the pycnocomolides possess marked inhibitory action on dopamine-mediated behavioural effects in mice and that further studies are required to elucidate the probable mechanism of this effect.