In different parts of India, Bombax malabaricum DC. (Family: Bombacaceae), a lofty deciduous tree with large leaves, is traditionally used in inflammation. The aim of the present study was to confirm its antiinflammatory activity and to search for the possible mechanism of action for methanol extract of Bombax malabaricum leaves (MEBM). The anti-inflammatory activity of MEBM was evaluated in a carrageenan-induced model of acute inflammation. As inflammation usually involves increased nitric oxide (NO) production, effect of MEBM on lipopolysaccharide-induced NO production in mouse peritoneal macrophages was studied to evaluate its possible mechanism of action. It was found that MEBM was non-toxic up to a dose of 2 g/kg for mice and rats, orally. MEBM (100, 200, and 400 mg/kg) significantly reduced carrageenan-induced rat paw edema (p < 0.05, p < 0.01, p < 0.001, respectively). In mice peritoneal macrophages, the IC50 for MEBM was 258.33 +/- 6.96 microg/mL and it was non-toxic up to 125 microg/mL. MEBM (0-100 microg/mL) reduced lipopolysaccharide-induced NO production in macrophages in a dose-dependent fashion (p < 0.001). Hence, MEBM possesses antiinflammatory activity, mediated through inhibition of NO production.
