Adjuvant activities of saponins from traditional Chinese medicinal herbs

New generation vaccines such as recombinant, antigen purified and DNA vaccines are poorly immunogenic due to the lack of an innate immune stimulus. Therefore, search of new adjuvants for these vaccines has become a topic of interesting. In new adjuvant development, saponins are outstanding candidates. Recently, increased attention has been received on plant-derived saponins in search of new adjuvant candidates from traditional Chinese medicinal herbs such as Panax ginseng, Astragalus species, Panax notoginseng,Cochinchina momordica, Glycyrrhiza uralensis and Achyranthes bidentata. Many of the saponins have been found to have adjuvant effects on purified protein antigens. The chemical structures of the saponins are related to their adjuvant activities, and influence the nature of the immune responses. Saponin adjuvants have been reported to stimulate secretion of a broad range of cytokines, suggesting that saponins may act by triggering innate immunity. As these plant-originated adjuvants may promote different branches of the immune system, they have the potential to be used in design of new vaccines so as to induce a desired immune response.