Saponin

Saponins are the glycosides of 27 carbon atom steroids, or 30 carbon atom triterpenes. They are found in various parts of the plant: leaves, stems, roots, bulbs,blossom,and fruit.. Saponins dissolve in water to form a stable soapy froth; this is thought to be due to their amphiphilic nature. The word sapon means 'soap', referring to the permanent froth saponins make on being mixed with water. They are also characterized by their bitter taste, and their ability to hemolyze red blood cells. Soapwort, Saponaria officinalis also called "Bouncing Bet" in the carnation family is the quintessential saponin-producing plant. The plant contains mildly poisonous saponins, as reflected in the genus name from the Latin sapo, meaning soap.

The botanical family Sapindaceae with its defining member, the genus Sapindus (soapberry) or (soapnut), includes 2000 species in 150 genera; and now including new family members, Aceraceae (maples) and Hippocastanaceae (horse chestnuts). Removal of the sugar moiety (hexoses, pentoses, and saccharic acids) from a saponin by complete hydrolysis, yields the aglycone, sapogenin. Diosgenin from the Mexican wild yam when subjected to the Marker degradation yields the synthetic hormone progesterone, the basis for combined oral contraceptive pill or simply "the pill." It was also the starting material for a cheap and plentiful supply of cortisone.

Saponins are highly toxic to cold-blooded animals, due to their ability to lower surface tension. Saponin as the sapogenin aglycone have also been identified in the animal kingdom in snake venom, starfish, and sea cucumber.

Saponins are believed to be useful in the human diet for controlling cholesterol, but some (including those produced by the soapberry) are poisonous if swallowed and can cause urticaria (skin rash) in many people. Any markedly toxic saponin is known as a sapotoxin.

Saponins have been identified in:
 * Agave
 * Alfalfa
 * Aloe
 * Amaranth
 * Anadenanthera peregrina (seeds)
 * Angelica sinensis
 * Aralia chinensis
 * Aralia manshurica
 * Asparagus (as protodioscin)
 * Astragalus membranaceus
 * Bacopa monnieri
 * Boussingaultia
 * Bupleurum chinense
 * Calendula officinalis
 * Capsicum (chile and bell peppers; seeds only)
 * Chickweed
 * Chlorophytum species
 * Chlorogalum species; soap plants
 * Codonopsis pilosula (roots)
 * Conkers/horse chestnuts
 * Tuberous cucurbit species
 * Digitalis (as digitonin)
 * Echinodermata (starfish, brittle stars, sea urchins, sea cucumbers)
 * Elecampane (roots; as triterpene saponins; dammaranedienol)
 * Eleutherococcus senticosus
 * Fenugreek
 * Goldenrod
 * Gotu Kola
 * Grape skin
 * Gymnema sylvestre (leaves)
 * Gypsophila (baby's breath)
 * Hawthorn (leaves, flowers, berries; all species, most notably C. oxyacanthas)
 * Jiaogulan (Gynostemma pentaphyllum)
 * Liquorice
 * Lungwort (particularly leaves of P.officinalis)
 * Mullein
 * Olives
 * Onion (red variety)
 * Panax (as ginsenoside)
 * Platycodon grandiflorum (roots)
 * Polygala senega (roots)
 * Polygala tenuifolia
 * Quillaja saponaria (bark)
 * Quinoa
 * Phytolacca americana (pokeweed)
 * Rambutan
 * Salvia
 * Soapberry and many other members of the family Sapindaceae, including buckeyes
 * Saponaria (Soapwort, Bouncing Betty)
 * Schizandra chinensis
 * Shallots
 * Southern pea (Vigna unguiculata subsp. unguiculata)
 * Soybeans
 * Tribulus terrestris (as protodioscin)
 * Wild yam (as diosgenin)
 * Yucca
 * Zizyphus jujuba

and many other plants used in medicine or as food items.

Saponins are also mild detergents and are used commercially as well as for research. They are used in the British Museum as a mild detergent to gently clean ancient manuscripts. In laboratory studies saponins can be used at 0.04%-0.2% to permeabilize ("make holes in") the plasma membrane as well as the membranes of internal organelles such as ER and Golgi but does not penetrate the nuclear membrane. Therefore it is used in intracellular histochemistry staining to allow antibody access to intracellular proteins.

Because of its reversible nature on cells and its ability to permeabilize cells without destroying cell morphology, it is used in laboratory applications to treat live cells in order to facilitate peptide or reagents such as antibodies to enter cells instead of the harsher detergent triton X-100. It is also done on whole cell preparations such as cell smears and cytospins where the cell membrane is intact. It can also be done on frozen sections but is not used on fixed tissue sections. To preserve the permeabilizing effect, saponin has to be used in all processes involved in the staining steps or otherwise removed after reagent of interest has reached the cell.

Medicinal use
Hypercholestrolaemia, Hyperglycaemia, Antioxidant, Anti-cancer, Anti-inflammatory, Weight loss, Gentle blood cleanser

Agricultural use
Saponins extracted from Yucca and/or Quillaja saponaria plants are used in some "natural" spray adjuvant formulations due to the following surfactant properties that they impart:
 * Wetting agent
 * Penetrant
 * Humectant