Effects of Licorice and Its Active Principles on Carrageenan-Induced Edema of the Rat Hind-Paw

The anti-inflammatory effects of the aqueous extract of licorice (Glycyrrhizae Radix, GR), glycyrrhizin (GL). and 18β-glycyrrhetinic acid (GA) on carrageenan-induced edema of the rat hind-paw were compared. Tested drugs were administered orally 1 hr prior to the subplantar injection of 0.1 m1 mixture of 1 % lambda carrageenan into the right hind-paw of the rat. The edema formation during 1-6 hr was completely blocked by 5 mg/kg indomethacin (as a positive control) and was partially attenuated by 200 mg/kg GA. Both GL and GR, at the doses containing equivalent quantities of 100, 200, and 500 mg/kg of GL, had little effects on edema formation. In contrast to 200 mg/kg GA, 500 mg/kg GA facilitated and increased the carrageenan-induced edema formation. This result indicates that GA has very narrow margin of anti-inflammatory activity on carrageenan induced edema.