Saponins when mixed with water reduce the surface tension of water, allowing the formation of small stable bubbles. As a consequence of their surface-active properties, saponins are excellent foaming agents (very stable). Today, saponins are used in the manufacture of fire extinguisher foam, toothpaste, shampoos, liquid soaps, and cosmetics and to increase the foaming qualities of beer and soft drinks.
Soapbark, like the other so-called “soap plants” such as soapweed (Yucca glauca), soapwort (Saponaria Officinalis), and soap berries (Sapindus species), are relatively high in saponins, the substances that account for the long-lasting lather produced when parts of these plants are vigorously mixed with water. The antifungal and antibacterial properties of saponins are important in cosmetic applications, in addition to their emollient effects.
Saponins are also found in the botanical family Sapindaceae, with its defining genus Sapindus (soapberry or soapnut), and in the closely related families Aceraceae (maples) and Hippocastanaceae (horse chestnuts). It is also found heavily in Gynostemma pentaphyllum (GenusGynostemma, Family Cucurbitaceae) in a form called gypenosides, and ginseng or red ginseng (Genus Panax, Family Araliaceae) in a form called ginsenosides.
Within these families, this class of chemical compounds are found in various parts of the plant: leaves, stems, roots, bulbs, blossom and fruit. In the animal kingdom, saponins are found in most sea cucumbers and starfish.