Saponin

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Saponins are the glycosides of 27 carbon atom steroids, or 30 carbon atom triterpenes in plants. They are found in various parts of the plant: leaves, stems, roots, bulbs, blossom, and fruit. They are characterized by their bitter taste, and their ability to hemolyze red blood cells. 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).

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[edit] Soap

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. 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 two major commercial sources of saponins are Yucca schidigera of Baja California and Quillaja saponaria (soapbark tree) of Chile.[1] Native Americans used yucca to make soap. In Chile, quillaja bark was used as a shampoo traditionally. Saponin-containing sapindus soap nuts are a natural detergent which is used to clean clothes. Saponins are mild detergents used commercially as well as for research. They are used in the British Museum to gently clean ancient manuscripts.

[edit] Applications

Saponin liquid extract concentrate is sold or spray-dried and sold as a powder with carriers such as lactose and maltodextrin. 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 progestin, 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.

Soap nuts have gentle insecticidal properties and are traditionally used for removing lice from the scalp. Soap nuts are antimicrobial and are beneficial for septic systems and greywater. Soap nuts are used in the remediation of contaminated soil. Soap nuts are used by Indian and Indonesian jewelers to remove the tarnish from silver and other precious metals. Saponins are used in ore separation, photographic emulsions, cosmetics, and shampoos.[2]

Unpurified saponin extracts are used in food, mostly for their foaming properties. Yucca and quillaja create the foamy "head" in root beer. Many saponins are as much as 200 times sweeter than sugar.[3] When eaten by dogs and cats, yucca reduces dung odor.[4]

[edit] Toxicity

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. Some saponins (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. Digitalis-saponins have been used in high doses as arrow and spear poisons by African and South American natives. [5] Like all detergents, saponins are highly toxic if injected, because they cause hemolysis of blood cells. If eaten or swallowed, hydrolysis of the glycoside into its sugar moiety and aglycone or sapogenin reduces a saponin's toxicity. Ingested, the sapogenin is less toxic and not hemolytic. Native Americans eat Indian ice-cream made with Canada Buffaloberry, which contains saponins. Dog feeds often contain soybeans and beet pulp, which contain saponins that may be toxic to dogs.[6]

[edit] Medicinal use

Soap nuts (sapindus), especially Sapindus mukorossi, are used medically as an expectorant, emetic, and for treatment of excessive salivation, epilepsy, chlorosis, and migraines. Soap nuts are among the list of herbs and minerals in Ayurveda. They are a popular ingredient in Ayurvedic shampoos and cleansers. They are used in Ayurvedic medicine as a treatment for eczema, psoriasis, and for removing freckles.

Saponins are believed to be useful in the human diet for controlling cholesterol. The Maasai eat soup laced with bitter bark and roots containing saponins. Heart disease is nearly nonexistent among the Maasai, and their cholesterol is one third lower than the average U.S. citizen. Urban Massai who don't eat the traditional soup, do develop heart disease.[1] [7] Bile cholesterol is secreted into the intestine. Much of it is later reabsorbed into the body. Saponins bind to bile acids and cholesterol, so much of it is not reabsorbed, and instead excreted from the body. [8] Digitalis-type saponins strengthens heart muscle contractions, causing the heart to pump more efficiently.[9]

Saponins inhibit some kinds of cancer cell tumor growth in animals, particularly lung and blood cancers, without killing normal cells. Cancer cells contain more cholesterol compounds than normal cells. Saponins bind to cholesterol, interfering with cell growth and division. In the colon, bacteria metabolize primary bile acids into secondary bile acids, which are a cause of colon cancer. Saponins bind to primary bile acids, preventing much of the secondary bile acids from forming.[10][11]

Saponins are the plants' immune system, acting as a natural antibiotic to protect the plant against microbes and fungus. Quillaja saponins stimulate the immune system and enhance both injected and oral vaccines. Saponin kills protozoa in the intestines by causing it's cell membrane to lyse.[12] Scientists are experimenting with saponin-based antibiotics, fungicides, yeast disinfectants, and vaccines against HIV.[13][14]

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.

[edit] List of plants containing saponins

Saponins have been identified in:

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

[edit] References

  1. ^ National Geographic Oct. 1995, page 161
  2. ^ PlantaMed (Portuguese)

[edit] External links

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Types of Glycosides
Bond:
Geometry:
Glycone:
Aglycone:
Alcoholic glycoside | Anthraquinone glycoside | Coumarin glycoside | Cyanogenic glycoside | Flavonoid glycoside | Phenolic glycoside | Saponin | Cardiac glycoside | Steviol glycoside | Thioglycoside | Glycosylamine | Bufanolide | Cardenolide
Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Nucleotide sugars | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides