ANTIMICROBIAL SAPONINS OF YUCCA-SCHIDIGERA AND THE IMPLICATIONS OF THEIR IN-VITRO PROPERTIES FOR THEIR IN-VIVO IMPACT

The benefits of supplementing livestock diets with extracts from Yucca schidigera have been attributed to inhibition of selected gut microbe s. The antimicrobial constituents were identified as three butanol-ext ractable 5 beta-spirostan-3 beta-ol saponins using Bacillus pasteurii and Saccharomyces cerevisiae as test prokaryotic and eukaryotic organi sms, respectively. Although these saponins inhibited microbial growth at low cell densities, their impact was associated with adsorption to the microbes and they had no effect on dense microbial populations. Th e antimicrobial saponins were also observed to adsorb to the microbiot a and other solids of the porcine cecum. The implications for gut micr obes differ according to their ecological niche: Those sequestered to feed particles or the gut lining may accumulate saponins, whereas thos e flushed out synchronously with the digesta should be protected by hi gh population densities.