Saponin
Encyclopedia
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. More specifically, they are amphipathic glycoside
s grouped, in terms of phenomenology
, by the soap-like foaming they produce when shaken in aqueous solutions, and, in terms of structure, 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.
(glycoside-free portion) of the saponins are termed sapogenin
s. The number of saccharide chains attached to the sapogenin/aglycone core can vary giving rise to another dimension of nomenclature (monodesmosidic, bidesmosidic, etc.) as can the length of each chain. A somewhat dated compilation has the range of saccharide chain lengths being 1–11, with the numbers 2-5 being the most frequent, and with both linear and branched chain saccharides being represented. Dietary monosaccharides such as D-glucose and D-galactose
are among the most common components of the attached chains.
The lipophilic aglycone can be any one of a wide variety of polycyclic
organic structures originating from the serial addition of ten-carbon (C10) terpene
units to compose a C30 triterpene skeleton, often with subsequent alteration to produce a C27 steroidal skeleton. The subset of saponins that are steroidal have been termed saraponins; Aglycone derivatives can also incorporate nitrogen, so that some saponins also present chemical and pharmacologic characteristics of alkaloid
natural products. The figure at right above presents the structure of the alkaloid phytotoxin
solanine
, a monodesmosidic, branched-saccharide steroidal saponin. (The lipophilic steroidal structure is the series of connected six- and five-membered rings at the right of the structure, while the three oxygen-rich sugar rings are at left and below. Note the nitrogen atom inserted into the steroid skeleton at right.)
, Family Caryophyllaceae
), the root of which was used historically as a soap. 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; ref. needed). It is also found heavily in Gynostemma pentaphyllum (Genus Gynostemma, Family Cucurbitaceae
) in a form called gypenosides, and 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. Commercial formulations of plant-derived saponins e.g., from the soap bark (or soapbark) tree, Quillaja saponaria, and from other sources—are available via controlled manufacturing processes, which make them of use as chemical and biomedical reagents.
, 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.
Many of California's Native American
tribes traditionally used soaproot, (genus Chlorogalum), which contains saponin, as a fish poison. They would pulverize the roots, mixing in water to create a foam, and then add the suds to a stream. This would kill or incapacitate the fish, which could be gathered easily from the surface of the water. Among the tribes using this technique were the Lassik, the Luiseño, the Yuki, the Yokut, the Chilula, the Wailaki, the Miwok, the Kato, the Mattole, the Nomlaki and the Nishinam
.
) on intravenous injection. In addition, the amphipathic nature of the class gives them activity as surfactant
s that can be used to enhance penetration of macromolecule
s such as protein
s through cell membranes. Saponins have also been used as adjuvant
s in vaccines.
Saponins from the Gypsophila paniculata (Baby’s Breath) plant have been shown to very significantly augment the cytotoxicity of immunotoxins and other targeted toxins directed against human cancer cells. The research groups of Professor Hendrik Fuchs (Charité University, Berlin, Germany) and Dr David Flavell
(Southampton General Hospital, United Kingdom) are working together toward the development of Gypsophila saponins for use in combination with immunotoxins or other targeted toxins for patients with leukaemia, lymphoma
and other cancers.
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 adjuvant
s 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.
Glycoside
In chemistry, a glycoside is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme...
s grouped, in terms of phenomenology
Phenomenology (science)
The term phenomenology in science is used to describe a body of knowledge that relates empirical observations of phenomena to each other, in a way that is consistent with fundamental theory, but is not directly derived from theory. For example, we find the following definition in the Concise...
, by the soap-like foaming they produce when shaken in aqueous solutions, and, in terms of structure, by their composition of one or more hydrophilic glycoside moieties combined with a lipophilic
Lipophilic
Lipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true...
triterpene
Triterpene
Triterpenes are terpenes consisting of six isoprene units and have the molecular formula C30H48.The pentacyclic triterpenes can be classified into lupane, oleanane or ursane groups.Animal- and plant-derived triterpenes exist, such as:*squalene...
derivative. A ready and therapeutically relevant example is the cardio-active agent digoxin
Digoxin
Digoxin INN , also known as digitalis, is a purified cardiac glycoside and extracted from the foxglove plant, Digitalis lanata. Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin...
, from common foxglove.
Structural variety and biosynthesis
The aglyconeAglycone
An aglycone is the non-sugar compound remaining after replacement of the glycosyl group from a glycoside by a hydrogen atom. The spelling aglycon is sometimes encountered .Classes of phytochemicals found in the aglycone and glycosides forms :...
(glycoside-free portion) of the saponins are termed sapogenin
Sapogenin
Sapogenins are the aglycones, or non-saccharide, portions of the family of natural products known as saponins. Sapogenins contain steroid or other triterpene frameworks as their key organic feature. For example, steroidal sapogenins like tiggenin, neogitogenin, and tokorogenin have been isolated...
s. The number of saccharide chains attached to the sapogenin/aglycone core can vary giving rise to another dimension of nomenclature (monodesmosidic, bidesmosidic, etc.) as can the length of each chain. A somewhat dated compilation has the range of saccharide chain lengths being 1–11, with the numbers 2-5 being the most frequent, and with both linear and branched chain saccharides being represented. Dietary monosaccharides such as D-glucose and D-galactose
Galactose
Galactose , sometimes abbreviated Gal, is a type of sugar that is less sweet than glucose. It is a C-4 epimer of glucose....
are among the most common components of the attached chains.
The lipophilic aglycone can be any one of a wide variety of polycyclic
Polycyclic compound
In organic chemistry, a polycyclic compound is a cyclic compound with more than one hydrocarbon loop or ring structures . In general, the term includes all polycyclic aromatic compounds, including the polycyclic aromatic hydrocarbons, the heterocyclic aromatic compounds containing sulfur,...
organic structures originating from the serial addition of ten-carbon (C10) terpene
Terpene
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...
units to compose a C30 triterpene skeleton, often with subsequent alteration to produce a C27 steroidal skeleton. The subset of saponins that are steroidal have been termed saraponins; Aglycone derivatives can also incorporate nitrogen, so that some saponins also present chemical and pharmacologic characteristics of alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
natural products. The figure at right above presents the structure of the alkaloid phytotoxin
Phytotoxin
Phytotoxin refers to a substance produced by a plant that is toxic or a substance that is toxic to the plant Many substances produced by plants are secondary metabolites and are the by-products of primary physiological processes...
solanine
Solanine
Solanine is a glycoalkaloid poison found in species of the nightshade family , such as the potato . It can occur naturally in any part of the plant, including the leaves, fruit, and tubers. Solanine has fungicidal and pesticidal properties, and it is one of the plant's natural defenses...
, a monodesmosidic, branched-saccharide steroidal saponin. (The lipophilic steroidal structure is the series of connected six- and five-membered rings at the right of the structure, while the three oxygen-rich sugar rings are at left and below. Note the nitrogen atom inserted into the steroid skeleton at right.)
Sources of saponin
Saponins have historically been understood to be plant-derived, but they have also been isolated from marine organisms. Saponins are indeed found in many plants, and derive their name from the soapwort plant (Genus SaponariaSaponaria
Saponaria, also known as soapworts, is a genus of about 20 species of perennial herbs in the Caryophyllaceae, native to southern Europe and southwest Asia. The most familiar species in Europe is the Common Soapwort , locally simply known as "the Soapwort". They grow to a height of 10-60 cm, with...
, Family Caryophyllaceae
Caryophyllaceae
The Caryophyllaceae, commonly called the pink family or carnation family, is a family of flowering plants. It is included in the dicotyledon order Caryophyllales in the APG III system, alongside 33 other families, including Amaranthaceae, Cactaceae and Polygonaceae...
), the root of which was used historically as a soap. Saponins are also found in the botanical family Sapindaceae
Sapindaceae
Sapindaceae, also known as the soapberry family, is a family of flowering plants in the order Sapindales. There are about 140-150 genera with 1400-2000 species, including maple, horse chestnut and lychee....
, with its defining genus Sapindus
Sapindus
Sapindus is a genus of about five to twelve species of shrubs and small trees in the Lychee family, Sapindaceae, native to warm temperate to tropical regions in both the Old World and New World. The genus includes both deciduous and evergreen species. Members of the genus are commonly known as...
(soapberry or soapnut), and in the closely related families Aceraceae
Aceraceae
Aceraceae is a family of flowering plants also called the Maple Family. It contains two to four genera, depending upon the circumscription, of some 120 species of trees and shrubs. A common characteristic is that the leaves are opposite, and the fruit a schizocarp.The maples have long been known...
(maples) and Hippocastanaceae
Hippocastanaceae
thumb|230pxHippocastanaceae is the name given to a small group of trees and shrubs, when this group is treated as a family. Its most widespread genus is Aesculus . However, the American genus Billia and the Chinese genus Handeliodendron are also sometimes included in this family...
(horse chestnuts; ref. needed). It is also found heavily in Gynostemma pentaphyllum (Genus Gynostemma, Family Cucurbitaceae
Cucurbitaceae
The plant family Cucurbitaceae consists of various squashes, melons, and gourds, including crops such as cucumber, pumpkins, luffas, and watermelons...
) in a form called gypenosides, and ginseng
Ginseng
Ginseng is any one of eleven species of slow-growing perennial plants with fleshy roots, belonging to the genus Panax of the family Araliaceae....
(Genus Panax, Family Araliaceae
Araliaceae
Araliaceae is a family of flowering plants, also known as the Aralia family or Ivy family. The family includes 254 species of trees, shrubs, lianas and perennial herbaceous plants into 2 subfamilies...
) 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. Commercial formulations of plant-derived saponins e.g., from the soap bark (or soapbark) tree, Quillaja saponaria, and from other sources—are available via controlled manufacturing processes, which make them of use as chemical and biomedical reagents.
Role in plant ecology and impact on animal foraging
In plants, saponins may serve as anti-feedants, and to protect the plant against microbes and fungi. Some plant saponins (e.g. from oat and spinach) may enhance nutrient absorption and aid in animal digestion. However, saponins are often bitter to taste, and so can reduce plant palatability (e.g., in livestock feeds), or even imbue them with life-threatening animal toxicity. Data make clear that some saponins are toxic to cold-blooded organisms and insects at particular concentrations. There is a need for further research to define the roles of these natural products in their host organisms, which have been described as "poorly understood" to date.Saponins in Ethnobotany
Most saponins, which readily dissolve in water, are poisonous to fish. Therefore, in ethnobotanyEthnobotany
Ethnobotany is the scientific study of the relationships that exist between people and plants....
, 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.
Many of California's Native American
Native Americans in the United States
Native Americans in the United States are the indigenous peoples in North America within the boundaries of the present-day continental United States, parts of Alaska, and the island state of Hawaii. They are composed of numerous, distinct tribes, states, and ethnic groups, many of which survive as...
tribes traditionally used soaproot, (genus Chlorogalum), which contains saponin, as a fish poison. They would pulverize the roots, mixing in water to create a foam, and then add the suds to a stream. This would kill or incapacitate the fish, which could be gathered easily from the surface of the water. Among the tribes using this technique were the Lassik, the Luiseño, the Yuki, the Yokut, the Chilula, the Wailaki, the Miwok, the Kato, the Mattole, the Nomlaki and the Nishinam
Nisenan
The Nisenan, also known as the Southern Maidu and Valley Maidu, are one of many native groups of the Central Valley. The name Nisenan, derives from the ablative plural pronoun nisena·n, "from among us"...
.
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 (hemolysisHemolysis
Hemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
) on intravenous injection. In addition, the amphipathic nature of the class gives them activity as surfactant
Surfactant
Surfactants are compounds that lower the surface tension of a liquid, the interfacial tension between two liquids, or that between a liquid and a solid...
s that can be used to enhance penetration of macromolecule
Macromolecule
A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles...
s such as protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s through cell membranes. Saponins have also been used as adjuvant
Adjuvant
An adjuvant is a pharmacological or immunological agent that modifies the effect of other agents, such as a drug or vaccine, while having few if any direct effects when given by itself...
s in vaccines.
Saponins from the Gypsophila paniculata (Baby’s Breath) plant have been shown to very significantly augment the cytotoxicity of immunotoxins and other targeted toxins directed against human cancer cells. The research groups of Professor Hendrik Fuchs (Charité University, Berlin, Germany) and Dr David Flavell
David Flavell
Dr David J Flavell BSc PhD FRCPath is a British academic research scientist specialising in the development of antibody-based treatments for adults and children with various forms of leukaemia and lymphoma....
(Southampton General Hospital, United Kingdom) are working together toward the development of Gypsophila saponins for use in combination with immunotoxins or other targeted toxins for patients with leukaemia, lymphoma
Lymphoma
Lymphoma is a cancer in the lymphatic cells of the immune system. Typically, lymphomas present as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and can be curable depending on the histology, type, and stage...
and other cancers.
Medical uses
There is tremendous, commercially driven promotion of saponins as dietary supplements and nutriceuticals. There is evidence of the presence of saponins in traditional medicine preparations, 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 sensitivityMultiple chemical sensitivityMultiple chemical sensitivity is a chronic medical condition characterized by symptoms the affected person attributes to exposure to low levels of chemicals. Commonly suspected substances include smoke, pesticides, plastics, synthetic fabrics, scented products, petroleum products and paints...
, 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 adjuvant
Adjuvant
An adjuvant is a pharmacological or immunological agent that modifies the effect of other agents, such as a drug or vaccine, while having few if any direct effects when given by itself...
s in the production of vaccines, toxicity associated with sterol complexation remains a major issue for attention. Even in the case of digoxin
Digoxin
Digoxin INN , also known as digitalis, is a purified cardiac glycoside and extracted from the foxglove plant, Digitalis lanata. Its corresponding aglycone is digoxigenin, and its acetyl derivative is acetyldigoxin...
, 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.
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 different authors.
- How to survive the world's worst diet
- Quillia Extracts JECFA Food Additives Series 48