Protective effect of saikosaponin A, saikosaponin D and saikogenin D against Pseudomonas aeruginosa infection in mice.

Effects of saikosaponins and their genins on nonspecific resistance against Pseudomonas aeruginosa and Listeria monocytogenes infections were investigated. When mice were administered intraperitoneally (i.p.) saikosaponins one day before i.p. infection with P. aeruginosa, saikosaponins a and d induced a marked enhancement of nonspecific resistance at a dose of 10 micrograms/mouse. Also, saikogenin D, a secondary metabolite of saikosaponin d, showed an enhancing effect. The most effective condition for enhancing the nonspecific resistance was i.p. administration of saikosaponin d one day before i.p. or intravenous (i.v.) infection with P. aeruginosa, when mice were treated i.p., i.v., or subcutaneously with saikosaponin d 1, 4 or 7 days previously. Effect of saikosaponin d was weaker than that of formalin-killed bacilli of Propionibacterium acnes and lipopolysaccharide. On the other hand, effect of saikosaponin d on enhancement of nonspecific resistance against L. monocytogenes was not seen. Effector cells participating in the enhanced protection induced by saikosaponin d may be macrophages, since macrophages were a major component in peritoneal cells obtained from mice administered i.p. saikosaponin d 1 day earlier and intracellular bactericidal activity of peritoneal macrophages against P. aeruginosa increased.