Inhibition of lipoxygenases and cyclooxygenase-2 enzymes by extracts isolated from Bacopa monniera (L.) Wettst

Abstract

Aim of the study Bacopa monniera Linn is described in the Ayurvedic Materia Medica, as a therapeutically useful herb for the treatment of inflammation. In the current study, we investigated the anti-inflammatory activity of methanolic extract of Bacopa monniera (BME). For some experiments EtOAc and bacoside fractions were prepared from BME. The effect of these extracts in modulating key mediators of inflammation was evaluated. Materials and methods Carrageenan-induced rat paw edema, rat mononuclear cells and human whole blood assay were employed as in vivo and in vitro models. Results In carrageenan-induced rat paw edema, BME brought about 82% edema inhibition at a dose of 100 mg/kg i.p. when compared to indomethacin (INDO) (3 mg/kg) that showed 70% edema inhibition. BME also significantly inhibited 5-lipoxygenase (5-LOX), 15-LOX and cyclooxygenase-2 (COX-2) activities in rat monocytes in vivo. Among the fractions tested in vitro, EtOAc fraction possessed significant 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity with IC 50 value of 30 μg/ml compared to butylated hydroxyl toluene (IC 50 = 13 μg/ml). This fraction also exerted significant hydroxyl radical scavenging activity with IC 50 value of 25 μg/ml in comparison with quercetin (IC 50 = 5 μg/ml). Inhibitory effects of EtOAc and bacoside fractions on LOX and COX activities in Ca-A23187 stimulated rat mononuclear cells were also assessed. 5-LOX IC 50 values were 25 μg/ml for EtOAc, 68 μg/ml for bacosides and 2 μg/ml for nordihydroguaiaretic acid (NDGA) where as COX-2 IC 50 values were 1.32 μg/ml for EtOAc, 1.19 μg/ml for bacoside fraction and 0.23 μg/ml for indomethacin. EtOAc and bacoside fractions also brought about significant decrease in TNF-α release ex vivo. Conclusion Bacopa monniera possesses anti-inflammatory activity through inhibition of COX and LOX and downregulation of TNF-α.