Esculentoside A (EsA) is a kind of saponin isolated from Phytolacca esculenta Van Houtte. It was shown to significantly inhibit phagocytic activity, intracellular and extracellular production of interleukin-1 by thioglycollate primed murine peritoneal macrophages in vitro at the concentration 0.01-1.0 mumol.L-1. In vivo experiments showed that EsA 2.5-5 mg.kg-1 markedly decreased serum hemolysin concentration in sensitized mice challenged with sheep red blood cells. Inhibition of antibody production by B lymphocytes, phagocytosis and the production of inflammatory mediators by macrophages may partially explain the wide and strong anti-inflammatory effect of EsA.