Actual and potential applications of and saponins in human and animal nutrition

Abstract

Saponins are natural detergents (surfactants) found in a variety of plants. The two major commercial sources of saponins are desert plants: Yucca schidigera from Mexico and Quillaja saponaria from Chile. Yucca saponins have a steroid nucleus, whereas Quillaja saponins are triterpenoid in structure. Saponins contain a lipophylic nucleus (steroid or triterpenoid) and one or more water-soluble carbohydrate side chains. Thus, the surfactant activity is a result of both fat-soluble and water-soluble moieties in the same molecule. There are several current and potential applications of yucca and Quillaja products in animal nutrition. Yucca extract is used as a feed additive to reduce ammonia and fecal odors in animal excreta. Saponins, by virtue of their surfactant properties, have antiprotozoal activity. Saponins have membranolytic properties; they complex with cholesterol in protozoal cell membranes, causing cell lysis. They have antibacterial activity and modify ruminal fermentation by suppressing ruminal protozoa and selectively inhibiting some bacteria. Ruminal ammonia concentrations are reduced. Yucca extract is used for prevention and treatment of arthritis in horses, although convincing evidence of its efficacy has not been reported. Saponins influence absorption of lipids, through formation of micelles with bile salts and cholesterol in the intestine. Quillaja saponins are used as adjuvants in veterinary vaccines. They are effective in both injected and orally administered vaccines, through saponin effects on cell membranes. There is evidence that oral administration of saponins may stimulate the immune system and increase resistance to a disease challenge. Yucca extract has been shown to reduce neonatal pig mortality when fed to sows in late pregnancy. Thus, dietary saponin sources have several beneficial properties in animal production.