Prebiotic effect of diosgenin, an immunoactive steroidal sapogenin of the Chinese yam

This study investigated the effect of diosgenin, a yam-derived phytochemical, on the growth of enteric lactic acid bacteria (LAB). The in vivo effect of diosgenin on the density of intestinal flora was examined in a murine model of food allergy. Oral administration with diosgenin markedly restored the diminished density of faecal LAB associated with allergic reactions. The direct effect of diosgenin and several structure-related steroidal compounds on the growth of faecal anaerobes isolated from diosgenin-administered mice was also investigated. The presence of diosgenin significantly enhanced the growth of Lactobacillus murinus and Lactobacillus reuteri, but not enterococci. Structure–activity relationship analysis showed that the prebiotic activity of steroidal sapogenins might require structural elements of the C5–C6 double bond and intact E- and F-rings. Collectively, these results indicate that steroidal sapogenins may be a novel class of prebiotics to LAB.