Effects of triterpene saponins from Astragalus species on in vitro cytokine release

Abstract

Roots of Astragalus species are used to treat leukemia and for wound healing in Turkish folk medicine. In order to evaluate this information, the effect of 13 cycloartane- and 1 oleanan-type triterpene saponins isolated from Turkish species (Astragalus brachypterus, Astragalus cephalotes, Astragalus microcephalus, and Astragalus trojanus), as well as methanol extracts from the roots of three Astragalus species (Astragalus cephalotes, Astragalus oleifolius and Astragalus trojanus) were studied. Cytokine concentrations of interleukins IL-1beta, IL-8 and TNF-alpha after bacterial lipopolysaccharide (LPS) and IL-2, IL-4 and INF-gamma after phorbolacetate (PHA) stimulation were determined using commercial enzyme-linked immunosorbent assay (ELISA) kits. All triterpene saponins tested in the present study showed a prominent IL-2 inducing activity between 35.9% and 139.6%. Among the extracts the highest score was obtained for Astragalus oleifolius (141.2%). Glycosides of 20,24-epoxy and 20,25-epoxy cycloartanes showed higher IL-2 inducing activity than those of acyclic-cycloartane derivatives as well as aglycone of 20,24-epoxy cycloartanes, cycloastrogenol. Especially the activity of Astragaloside VII, a tridesmosidic glycoside of cycloastrogenol, was the most remarkable. The oleanan-type triterpene saponin also showed a prominent IL-2 inducing activity. IL-2 is a cytokine produced by activated T cells, which has shown powerful immunostimulatory and antineoplastic properties. Accordingly, the IL-2 inducing activity of the triterpene saponins might be the mechanism involved in order to explain the immunomodulatory and anticancer effects of Astragalus species.