The methanol seed extract of Carica papaya (CPE) was investigated for antinociceptive and anti-inflammatory activities in mice and rats. The brine shrimp lethality test of the extract showed LC50 of 106.94 ppm at 95% confidence interval. The extract (5, 10 and 20 mg/kg, p.o.) significantly (p < 0.05) increased pentobarbitone-induced sleeping time by more than 280% compared with the control. Like pethidine (9.1 mg/kg, i.p.), CPE (10 and 20 mg/kg, p.o.) significantly (p < 0.05) decreased the paw licking time in early (0 - 5 min) and late (25 - 30 min) phases of formalin-induced nociception. This antinociceptive effect was more in the late phase than early phase. Also, CP (5, 10 and 20 mg/kg, p.o.) significantly (p < 0.05) decreased the number of acetic acid-induced abdominal contortions by 25, 60 and 64%, respectively. Indomethacin (10 mg/kg, p.o.), CPE (5, 10 and 20 mg/kg, p.o.) showed a typical biphasic anti-inflammatory effect in carrageenin-induced paw oedema in rats. The anti-inflammatory effect though moderate, was dose-dependent and higher in 2 h than 4 h after administration of the phlogistic agent. In conclusion, CPE contains potent bioactive compounds (alkaloids, flavonoids and polyphenols) which showed antinociceptive effect probably mediated centrally and peripherally; and also involving mild anti-inflammatory mechanisms.
Key words: Carica papaya, brine shrimps, antinociception, anti-inflammatory.
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