Inhibitory Effects of Baicalein and Wogonin on Lipopolysaccharide‐Induced Nitric Oxide Production in Macrophages

Abstract

In order to elucidate the mechanism of the antiinflammatory action of baicalein and wogonin, flavonoids from the root of Scutellaria baicalensis, the effects of these compounds were investigated on lipopolysaccharide‐induced nitric oxide production in a macrophage‐derived cell line, RAW 264.7. Baicalein (5–25 μM) and wogonin (5–50 μM) inhibited lipopolysaccharide‐induced nitric oxide generation in a concentration‐dependent manner. The inhibitory effect of these compounds was observed only when they were added at the start of cell incubation soon after the stimulation with lipopolysaccharide. Baicalein (25 μM) and wogonin (25 μM) also inhibited protein expression of inducible nitric oxide synthase. This inhibitory effect of wogonin was stronger than that of baicalein, which agrees with the result that wogonin showed stronger inhibition of nitric oxide production than baicalein. These results suggest that baicalein and wogonin attenuate lipopolysaccharide‐stimulated nitric oxide synthase induction in macrophages and thus may help to explain the antiinflammatory action of these flavonoid compounds.