Thesis (M.Sc. in Pharm.)--Chulalongkorn University, 2008

Curcumin is the important active responsible for the biological activity of Curcumin loga L. We initially determined the antinociceptive property of a range of synthetic curcumin does in the mouse hot-plate test. Hot-plate(cut-off 45 sec)were determined in male ICR mice prior to the administration of 0.9% normal saline solution (NSS; 10 mg, i.p.), morphine(MO; 10 mg/kg, i.p.) 0.5% carboxymethylcellulose(CMC;10 ml/kg, p.o.)or varios doses of synthetic curcumin(25-400 mg/kg, p.o.). Hot-plate latencies were subsequently determined at 15, 30, 45,60,90,120 and240 min. The percent maximum possible effect(%MPE) was calculated and used in the determination of the area of analgesia(%MPE-min). All doses of curcumin tested produced a significant analgesic response. Curcumin 200 mg/kg produced analgesic response that was naloxone-sensitive suggesting opioid-mediated mechanism. In the mouse tail-flick test, tail-flick latencies(cut-off 4 sec) were determined prior to the administrstion of NSS, MO, 0.5%CMC or various does of synthetic curcumin(25-400 mg/kg)and were subsequently determined at 7 intervals over a 4 hr period. All doses of curcumin tested failed to produce analgesic response. In acetic acid-induced writhing in mice, the animals were intraperitoneal injection of 0.6% acetic acid(10 ml/kg) 1 hr after the administration of NSS, indomethacin (IND, 10 mg/kg, p.o.), 0.5% CMC or various doses of synthetic curcumin(25-400 mg/kg, p.o.)and the mean writhing response was determined for 30 mined for 30 min. Curcumin 200 and 400 mg/kg significantly(ρ˂0.05)decreased the mean writhing response compared to vehicle controls. In the Randall-Selitto test, rats were injected with carrageenan into the plantar of the left hind paw 1 hr. after the administration of NSS, indomethacin(IND; 10 mg/kg, p.o.), 0.5%CMC or various doses of synthetic curcumin(25-400 mg/kg, p.o.)and the mean paw withdrawal threshold were threshold were determinined over a 4 hr period. Curcumin 200 mg/kg significantly (ρ˂0.05) increased meanpaw withdrawal thresholds up to 4 hr. after carrageenan administration. Studies then determined the anti-inflammatory property of orally administered synthetic curcumin (25-400 mg/kg) using carrageenan-induced paw edema test in rats. All doses of curcumin significantly reduced paw volume during the second phase of edema. Taken together these results demonstrated that synthetic curcumin produced both central and peripheral analgesic activity and mechanism of action seems to be related to opioid receptors. The mechanism of anti-inflammatory effect of curcumin may involve in the inhibition of prostaglandin synthesis.