Saponins are chemical compounds abundant in different types of plant species. They are among the secondary metabolites and produce soap-like foam when they are shaken in water solutions. Their structure is composed of one or more hydrophilic glycoside moieties held by a lipophilic triterpene derivative. Among the best examples of the presence of saponins is digoxin, a cardo-active agent derived from foxglove.
Saponins are made up of aglycone cores in which saccharide chains are attached to, the number of chains defining the length of the saponin. Dietary monosaccharides such as D-galactose and D-gluctose are among the common types of sugars found in saponins, and the length of the chains range from 2-5 and 1-11. The compounds' organic structures meanwhile originate from the ten-carbon terpene and form 30-carbon skeletons, where elements such as nitrogen can be found.
Initially, saponins are known to be derived from plants, but recent studies show that they are also present in marine organisms. They are commonly found in the soapwort plant, whose roots were once used as soap. They can also be derived from soapberries, maples, horse chestnuts and ginseng. Saponins can be extracted from the bark, leaves, stems, bulbs, fruits and flowers of these plants.
As saponins play a big role in historical medicine and hygiene, tests are conducted to see how they exactly work. According to research, saponins present in a given bark or plant attribute form a soapy foaming substance when mixed with water. Persistent foam tests in acidic solutions, as well as blood hemolysis tests are done to see the presence of saponins in a given mixture, as well as their capability to generate hemolysis.
Saponins by nature serve as anti-feedants. They also act as a shield against the penetration of microbes and fungi into the plant which can cause the latter's sickness and death. Other saponins further nutrient absorption and improve digestion especially to animals. They are however, bitter, and are hence not that appealing to the taste preferences of most warm-blooded animals (including humans).
As a medical ingredient, saponins act as and adjuvant in vaccines, but they have been used throughout history as dietary supplements and traditional medicine applications. Saponins mixed with water and prepared for oral administration is also common, as the mixture is expected to display hydrolysis of glycoside from terpenoid (as a form of chemical reaction). As a nutriceutial, saponins however, have the tendency to be toxic due to chemical sensitivity, thus their use for other more complex medical preparations have been limited.