Saponin

Saponins are a class of chemical compounds, one of many secondary metabolites found in natural sources, with saponins found in particular abundance in various plant species. Specifically, they are amphipathic glycosides grouped phenomenologically by the soap-like foaming they produce when shaken in aqueous solutions, and structurally by their composition of one or more hydrophilic glycoside moieties combined with a lipophilic triterpene derivative. A ready and therapeutically relevant example is the cardio-active agent digoxin, from common foxglove.

Structural variety and biosynthesis

The aglycone (glycoside-free portion) of the saponins are termed sapogenins. The number of saccharide chains attached to the sapogenin/aglycone core can vary giving rise to another dimension of nomenclature (monodesmosidic, bidesmosidic, etc. often with subsequent alteration to produce a C27 steroidal skeleton. Saponins are indeed found in many plants, and derive their name from the soapwort plant (Genus Saponaria, Family Caryophyllaceae), the root of which was used historically as a soap.

Role in plant ecology and impact on animal foraging

In plants, saponins may serve as anti-feedants,Therefore, in ethnobotany, saponins are primarily known for their use by indigenous people in obtaining aquatic food sources.

Since prehistoric times, cultures throughout the world have used piscicidal plants, mostly those containing saponins, for fishing.

Although prohibited by law, fish poison plants are still widely used by indigenous tribes in Guyana.

On the Indian sub-continent, the Gond tribes are known for their use of plant extracts in poison fishing.

Established research bioactivities and therapeutic claims

Bioactivities

One research use of the saponin class of natural products involves their complexation with cholesterol to form pores in cell membrane bilayers, e.g., in red cell (erythrocyte) membranes, where complexation leads to red cell lysis (hemolysis) on intravenous injection. In addition, the amphipathic nature of the class gives them activity as surfactants that can be used to enhance penetration of macromolecules such as proteins through cell membranes. where oral administrations might be expected to lead to hydrolysis of glycoside from terpenoid (and obviation of any toxicity associated with the intact molecule). But as is often the case with wide-ranging commercial therapeutic claims for natural products: the claims for organismal/human benefit are often based on very preliminary biochemical or cell biological studies; and mention is generally omitted of the possibilities of individual chemical sensitivity, or to the general toxicity of specific agents,) and high toxicity of selected cases.

While such statements require constant review (and despite the myriad web claims to the contrary), it appears that there are very limited US, EU, etc. agency-approved roles for saponins in human therapy. In their use as adjuvants in the production of vaccines, toxicity associated with sterol complexation remains a major issue for attention. Even in the case of digoxin, therapeutic benefit from the cardiotoxin is a result of careful administration of an appropriate dose. Very great care needs to be exercised in evaluating or acting on specific claims of therapeutic benefit from ingesting saponin-type and other natural products.

See also

Phytonutrients

Triterpenoid saponins

References

External links

Medical Dictionary on Saponin

Saponins in Wine, by ScienceDaily, accessed Sep 9,2003

Molecular Expressions Phytochemical Gallery - Saponin

Saponins: Suprising [sic] benefits of desert plants

Other uses of Quillaja Saponins and derived products, some works of diferent authors.

How to survive the world's worst diet

Quillia Extracts JECFA Food Additives Series 48

Category:Glycosides Category:Natural products Category:Plant toxins