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a) INDUSTRIAL APPLICATIONS
Saponins are the natural soap. They are used as foaming agents and emulsion stabilisers in drinks, confectionery, beer, soap and fire fighting fluids. Saponins serve as antioxidants added to manufactured foods.
b) THERAPEUTIC APPLICATIONS
The active principles in some of the therapeutically important plants like ginseng, liquorice, yams, digitalis, sarasparilla, etc., are saponins.
Steroidal saponins such as diosgenin, smilagenin and glycyrrhizin (from the species of Dioscorea, Smilax and Glycyrrhiza respectively) are used as precursors in the synthesis of hormones like cortisone. Terpenoidal saponins mimic the effects of corticotrophin (ACTH), the hormone of the anterior pituitary gland which specifically stimulates the adrenal cortex to produce corticoids.
Saponins have diverse therapeutic effects and function as bactericidal, anti-inflammatory, antipyrhetic, analgesic, spermicidal, antiulcer, anticholesterol and expectorant agents. The saponin in ginseng appears to calm down a person by depressing the central nervous system. Saponins in the much valued Indian medicinal plant, brahmi (Centella asiatica or Bacopa monnieri) are reputed to enhance memory. Dodonaea viscosa, a plant rich in saponins is used by bone setters and is believed to have the effects of anabolic steroids. Saponins are an ingredient in a patented antisnoring formulation. However, all saponins do not produce the same effects. For example, saponins from liquorice increase blood pressure while those from Yucca are hypotensive.
Saponins are currently preferred as human-safe immunological adjuvants to elicit higher titres of antibodies (Wu et al., 1992; Sangeetaa , 1994; Kensil et al., 1995; Kameswara Rao and Sangeetaa, 1997).
SAPONIONS IN OUR DIET
We regularly consume the saponins present in the plants we use as food. The estimated saponin content of some of the food items is given in Table 1.
Table 1
Saponin content of some food items
| Food Item |
Saponin content(upto g/kg) |
| Chick pea (channa) | 60 |
| Beet root | 58 |
| Soybean | 56 |
| Cluster bean (guar) | 50 |
| Spinach (palak) | 47 |
| Beans (different kinds) | 21 |
| Peanut | 16 |
| Mung bean (green gram) | 06 |
| Lentil | 05 |
| Green peas | 02 |
Though not quantified, the following also contain considerable amounts of saponins: potato, tomato, brinjal, onion, garlic, leek, oats, cabbage, bitter gourd, asparagus, and sesame; the universal beverage tea and the juice of the passion fruit; and the food additives, ajowan (carum), mustard, nutmeg and fenugreek (methi).
There has not been any systematic and intensive study on the occurrence of saponins in food and medicinal plants.
SAPONINS AND CHOLESTEROL
High serum cholesterol levels are associated with coronary heart disease, hypolipoproteinemia, hypothyroidism, nephrosis, diabetes, liver disease and gall stones. The general medical recommendation, the world over, is that serum cholestserol levels should be maintained about 200 mg/100 ml.
One of the potentially beneficial uses of saponins is their ability to lower the concentrations of cholesterol in blood plasma and organs like liver. This was observed some fifty years ago (Peterson, 1950) but somehow did not gain the recognition it deserves.