What Are Saponins?
Saponins are essentially a type of chemical substance, one of the numerous structures that are discovered in natural sources. In certain types of plants, saponins come in great numbers. Similarly, all saponins form a soapy foam when shaken in a solution.
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Saponins and Vectors
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Of particular interest is the use of saponins against the vector of the disease schistosmiasis, which is endemic in 76 countries and affects over 200 million people, mainly in tropical and subtropical regions. Other biological effects are cardiovascular, anti-inflammatory, antiexudative, immunomodulation, antiulcer, fungicidal, hemolytic, bitterness, sweetness, cholesterol-reducing ability in humans and animals and effects on capillary fragility. Spiroconnazole possesses strong molluscicidal activity against all snail vectors.
Ornithogalum Saundersiae
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A promising discovery comes from Ornithogalum saundersiae, a member of the lily family with no folkloric background of medicinal properties. From the bulb of this plant, Japanese workers have isolated a saponin tentatively named OSW-1. The compound has little toxicity to normal human cells, but is remarkably toxic to malignant tumor cells.
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Saponin Properties
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Saponins like mungbeans and horse chestnut can shape an intricate compund with cholesterol that inhibits absorption of cholesterol from the intestinal lumen. Other saponins may form large mixed micelles with bile acids, which also inhibit absorption from the small intestine leading to increased fecal excretion of the bile acids. Bile acids thus lost (and diverted from the enterohepatic cycle) are replaced by hepatic synthesis of cholesterol.
Saponin Interactions
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Saponins may interact with cholesterol or bile acids or both, and the details depend largely upon their molecular structure. In either case, the net result is a decrease in the concentration of cholesterol in the blood plasma. Within plant foods that have high concentrations of saponins, alfalfa saponins have been studied extensively, and their hypocholesterolemic activity is well documented. Alfalfa seeds have been shown to have a strong cholesterol-lowering effect in humans.
Use in Commerce
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Saponins may be used in commerce as pure compounds or mixtures. Some steroidal glycosides serve as starting materials for steroids used in oral contraceptives, and triterpene glycosides are used in fire extinguishers and as surfactants in soaps. Also, many products of major United States herbal manufacturers include saponin-containing plants.
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