Saponins are natural surfactants, or detergents, found in many plants, but they are most abundant in the desert plants Yucca and Quillaja. Extracts from these plants are commonly used as foaming agents for beverages such as root beer. These biochemicals also have commercial applications such as ore separation in industrial and mining operations, and are useful in products such as photographic emulsions, cosmetics, and shampoos.
Legumes, such peas and soybeans, also contain small quantities of saponins, which are proving their worthiness as phytochemicals. In the diet, phytochemical saponins have a wide spectrum of activity as antifungal and antibacterial agents, lowering of blood cholesterol, and inhibition of cancer cell growth. Recent studies have suggested that the low serum cholesterol levels of Masai tribes in East Africa — who consume a diet very high in animal products, cholesterol, and saturated fat — are probably due to the consumption of saponin-rich herbs. Saponins act by binding with bile acids and cholesterol, so it is thought that these chemicals “clean” or purge these fatty compounds from the body, lowering the blood cholesterol levels.
Some saponins affect the heart and have been used for over 100 years to treat heart conditions. Digitalis is one such saponin and is derived from the common garden plant, Foxglove. Digitalis strengthens contractions of the heart muscle and makes it work more efficiently in people with heart disease. Digitalis-type saponins can be toxic in high doses and have been used as arrow and spear poisons by African and South American natives.