Anti-Inflammatory Effects of a Polyphenol-Rich Spearmint Extract in a Rat Paw Edema Model

This study assessed the anti-inflammatory effects of a polyphenol-rich spearmint extract containing rosmarinic acid using a rat paw edema model. Four groups of male Wistar rats received intraperitoneal administration of either a proprietary spearmint extract containing 15% rosmarinic acid at doses of 10, 30 or 100 mg/kg (n=18), rosmarinic acid standard at doses of 15 or 50 mg/kg (n=10), Indomethacin, an anti-inflammatory agent, at 10 mg/kg (n=6), or saline alone as a vehicle control (n=10). Fifteen minutes later, subplantar injections of carrageenan (100 μl, 1%) were administered to induce paw edema in all animals with the exception of four animals in the saline control group who received a saline subplantar injection (saline-saline group). Paw volumes were assessed by the volume displacement method immediately after carrageenan injection (baseline) and 3 and 6 hours later. Paw edema was expressed as mean percent change of paw volume at 3 and 6 hours compared to baseline. As expected for the rats in the s...