Anti-inflammatory effect of Curcuma longa (turmeric) rhizome when administered topically in gel form

Curcuma longa L. (Zingiberaceae) rhizome (turmeric) is widely used in folk medicine of the Indian subcontinent for inflamed joints. The objective of the present study was to investigate the anti-inflammatory effects of turmeric when administered topically in gel form to carrageenan-induced paw edema in rats. Gels contained polyethylene glycol-6000, sodium carboxymethyl cellulose and isopropyl alcohol without and with turmeric powder or diclofenac. The right hind paw of all rats were pre-treated twice daily for 2 days with gel without (Group 1) or containing turmeric powder at 3.33, 10 and 33.3% w/v (Groups 2, 3 and 4, respectively). Group 5 rats were pre-treated with gel containing the standard anti-inflammatory drug diclofenac (1% w/v). Edema was induced on Day 3 by injecting 0.1ml of 1% carageenan solution (in normal saline) into the plantar surface of the right hind paw of each rat. Increase in paw volume was monitored up to 5 hours after injection. Significance levels of the results were calculated using Student's t-test and date were considered statistically significant when P<0.05. Pre-treatment with turmeric-containing gel produced a significant and dose-dependent inhibition of rat paw edema. Compared to controls, at the highest dose (33.3% turmeric), edema was inhibited by 53.4±2.6, 40.0±3.3, 36.3±2.8, 33.5±3.7 and 31.4±3.4%, respectively, at the first, second, third, fourth and fifth hour following carrageenan injection. These results compare favorably with diclofenac, where the respective inhibitions were 35.5±3.4, 36.5±3.3, 33.5±3.7, 29.5±3.0 and 24.5±4.0%. Even at the lowest dose (3.33%), turmeric inhibited paw edema by 27.4% at the first hour following carrageenan injection. The results validate the folk medicinal use of turmeric as an anti-inflammatory agent.