To evaluate the anti-endotoxin activity of surfactin C, we studied its lipopolysaccharide-binding activity in vitro and therapeutic efficacy in experimental models of gram-negative septic shock. The ability of surfactin C to bind LPS from Escherichia coli O111:B4 was determined using a limulus chromogenic assay. Male ICR mice and Sprague-Dawley rats were given intraperitoneal administration of 1x10(9) colony forming units of E. coli ATCC 25922. After bacterial challenge, all animals were randomized to receive intraperitoneally saline, polymyxin B or surfactin C. Surfactin C not only completely bound to the LPS (its median effective concentration being 13.75 microM) but also improved the survival and reduced of the number of inoculated bacteria in the mouse model of septic shock. Surfactin C reduced the plasma endotoxin, tumor necrosis factor-alpha and nitric oxide levels in response to septic shock in rats.