Antinociceptive activity of the alkaloid extract from Kopsia macrophylla leaves in mice

The effects of the alkaloid extract from the leaves of Kopsia macrophylla Hk. f. K. (K. macrophylla) on nociceptive response using writhing, hot plate and formalin test and the antipyretic activity in yeast-induced fever in mice, were examined. General behavior was also examined using pentobarbital-induced sleep in mice. The LD50 value of intraperitoneally injected K. macrophylla extract in mice was 318.46 mg/kg. Oral administration of K. macrophylla extract at the dose of 400 mg/kg significantly decreased the number of contortions and stretchings induced by acetic acid and licking activity of the late phase in the formalin test but not in the heat-induced pain in mice. The K. macrophylla extract (100-400 mg/kg, p.o.) had no effect on fever induced by yeast in mice. The alkaloid extract of K. macrophylla prolonged the duration of pentobarbitalinduced sleep in mice. These results suggest that the alkaloid extract of K. macrophylla possesses analgesic action via peripheral pathway but no antipyretic activity.