GC-MS analysis of a hot water extract of Herba Pogostemonis (HP) revealed the presence of 131 compounds. HP slightly inhibited Salmonella Typhimurium bacteria in culture and stimulated uptake of the bacteria into RAW 264.7 murine macrophage cells as indicated by both increased fluorescence from internalized FITC-dextran and increased colony-forming unit (CFU) counts of the lysed macrophages. Postinfection, the HP-treated cells showed lower bacterial counts than the control. HP elicited altered morphology, elevated inducible NO synthase (iNOS) mRNA, and reduced pro-inflammatory cytokine expression in macrophage cells. Salmonella induced increased expression of iNOS mRNA, cognate polypeptides, and NO. Histology of mice infected with a sublethal dose (1 × 10(4) CFU) of Salmonella showed that intraperitoneally administered HP protected against necrosis of the liver, a biomarker of in vivo salmonellosis. The lifespan of mice infected with a lethal dose (1 × 10(5) CFU) was significantly extended. These results suggest that the activity of HP against bacterial infection in mice occurs through the activation of innate immune macrophage cells. The relationship of composition of HP to bioactivity is discussed.