Saponins (Latin "sapon", soap + "-in", one of), also selectively referred to as triterpene glycosides, are bitter-tasting usually toxic plant-derived organic chemicals that have a foamy quality when agitated in water. They are widely distributed but found particularly in soapwort (genus Saponaria ), a flowering plant, the soapbark tree ( Quillaja saponaria ) and soybeans ( Glycine max L.). They are used in soaps, medicines, fire extinguishers, speciously as dietary supplements, for synthesis of steroids, and in carbonated beverages (for example, being responsible for maintaining the head on root beer). Saponins are both water and fat soluble, which gives them their useful soap properties. Some examples of these chemicals are glycyrrhizin (licorice flavoring) and quillaia (alt. quillaja), a bark extract used in beverages. [1] [2]
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Structurally, they are glycosides, which are sugars bonded to one or more organic molecules. In a glycoside molecule, the sugar is the glycone part, while one or more non-sugar organic molecules form the aglycone part.
Their aglycone is a triterpene. [3]
The saponins are a subclass of terpenoids, the largest class of plant extracts. The amphipathic nature of saponins gives them activity as surfactants with potential ability to interact with cell membrane components, such as cholesterol and phospholipids, possibly making saponins useful for development of cosmetics and drugs. [4] Saponins have also been used as adjuvants in development of vaccines, [5] such as Quil A, an extract from the bark of Quillaja saponaria . [4] [6] This makes them of interest for possible use in subunit vaccines and vaccines directed against intracellular pathogens. [5] In their use as adjuvants for manufacturing vaccines, toxicity associated with sterol complexation remains a concern. [7]
Quillaja is toxic when consumed in large amounts, involving possible liver damage, gastric pain, diarrhea, or other adverse effects. [6] The NOAEL of saponins is around 300 mg/kg in rodents, so a dose of 3 mg/kg should be safe with a safety factor (see Therapeutic index) of 100. [8]
Saponins are used for their effects on ammonia emissions in animal feeding. [9] In the United States, researchers are exploring the use of saponins derived from plants to control invasive worm species, including the jumping worm. [10] [11]
The principal historical use of these plants was boiling down to make soap. Saponaria officinalis is most suited for this procedure, but other related species also work. The greatest concentration of saponin occurs during flowering, with the most saponin found in the woody stems and roots, but the leaves also contain some.
Saponins have historically been plant-derived, but they have also been isolated from marine organisms such as sea cucumber. [1] [12] They derive their name from the soapwort plant (genus Saponaria , family Caryophyllaceae), the root of which was used historically as a soap. [1] [13] [2] Saponins are also found in the botanical family Sapindaceae, including its defining genus Sapindus (soapberry or soapnut) and the horse chestnut, and in the closely related families Aceraceae (maples) and Hippocastanaceae. It is also found heavily in Gynostemma pentaphyllum (Cucurbitaceae) in a form called gypenosides, and ginseng or red ginseng ( Panax , Araliaceae) in a form called ginsenosides. Saponins are also found in the unripe fruit of Manilkara zapota (also known as sapodillas), resulting in highly astringent properties. Nerium oleander (Apocynaceae), also known as White Oleander, is a source of the potent cardiac toxin oleandrin. Within these families, this class of chemical compounds is found in various parts of the plant: leaves, stems, roots, bulbs, blossom and fruit. [14] Commercial formulations of plant-derived saponins, e.g., from the soap bark tree, Quillaja saponaria , and those from other sources are available via controlled manufacturing processes, which make them of use as chemical and biomedical reagents. [15] Soyasaponins are a group of structurally complex oleanane-type triterpenoid saponins that include soyasapogenol (aglycone) and oligosaccharide moieties biosynthesized on soybean tissues. Soyasaponins were previously associated to plant-microbe interactions [16] from root exudates and abiotic stresses, as nutritional deficiency. [17]
In plants, saponins may serve as anti-feedants, [2] [18] and to protect the plant against microbes and fungi.[ citation needed ] 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. [18] Some saponins are toxic to cold-blooded organisms and insects at particular concentrations. [18] Further research is needed to define the roles of these natural products in their host organisms, which have been described as "poorly understood" to date. [18]
Most saponins, which readily dissolve in water, are poisonous to fish. [19] Therefore, in ethnobotany, they are known for their use by indigenous people in obtaining aquatic food sources. Since prehistoric times, cultures throughout the world have used fish-killing plants, typically containing saponins, for fishing. [20] [21] [22]
Although prohibited by law, fish-poison plants are still widely used by indigenous tribes in Guyana. [23]
On the Indian subcontinent, the Gondi people use poison-plant extracts in fishing. [24]
Many of California's Native American tribes traditionally used soaproot, (genus Chlorogalum) and/or the root of various yucca species, which contain saponin, as a fish poison. They would pulverize the roots, mix with water to generate a foam, then put the suds into 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, and the Mattole. [25]
The vast heterogeneity of structures underlying this class of compounds makes generalizations difficult; they're a subclass of terpenoids, oxygenated derivatives of terpene hydrocarbons. Terpenes in turn are formally made up of five-carbon isoprene units. (The alternate steroid base is a terpene missing a few carbon atoms.) Derivatives are formed by substituting other groups for some of the hydrogen atoms of the base structure. In the case of most saponins, one of these substituents is a sugar, so the compound is a glycoside of the base molecule. [1]
More specifically, the lipophilic base structure of a saponin can be a triterpene, a steroid (such as spirostanol or furostanol) or a steroidal alkaloid (in which nitrogen atoms replace one or more carbon atoms). Alternatively, the base structure may be an acyclic carbon chain rather than the ring structure typical of steroids. One or two (rarely three) hydrophilic monosaccharide (simple sugar) units bind to the base structure via their hydroxyl (OH) groups. In some cases other substituents are present, such as carbon chains bearing hydroxyl or carboxyl groups. Such chain structures may be 1-11 carbon atoms long, but are usually 2–5 carbons long; the carbon chains themselves may be branched or unbranched. [1]
The most commonly encountered sugars are monosaccharides like glucose and galactose, though a wide variety of sugars occurs naturally. Other kinds of molecules such as organic acids may also attach to the base, by forming esters via their carboxyl (COOH) groups. Of particular note among these are sugar acids such as glucuronic acid and galacturonic acid, which are oxidized forms of glucose and galactose. [1]
Cardiac glycosides are a class of organic compounds that increase the output force of the heart and decrease its rate of contractions by inhibiting the cellular sodium-potassium ATPase pump. Their beneficial medical uses are as treatments for congestive heart failure and cardiac arrhythmias; however, their relative toxicity prevents them from being widely used. Most commonly found as secondary metabolites in several plants such as foxglove plants, these compounds nevertheless have a diverse range of biochemical effects regarding cardiac cell function and have also been suggested for use in cancer treatment.
A glycosidic bond or glycosidic linkage is a type of ether bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate.
A steroid is an organic compound with four fused rings arranged in a specific molecular configuration.
Terpenes are a class of natural products consisting of compounds with the formula (C5H8)n for n ≥ 2. Terpenes are major biosynthetic building blocks. Comprising more than 30,000 compounds, these unsaturated hydrocarbons are produced predominantly by plants, particularly conifers. In plants, terpenes and terpenoids are important mediators of ecological interactions, while some insects use some terpenes as a form of defense. Other functions of terpenoids include cell growth modulation and plant elongation, light harvesting and photoprotection, and membrane permeability and fluidity control.
In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use. Many such plant glycosides are used as medications. Several species of Heliconius butterfly are capable of incorporating these plant compounds as a form of chemical defense against predators. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body.
Quillaia is the milled inner bark or small stems and branches of the soapbark. Other names include Murillo bark extract, Panama bark extract, Quillaia extract, Quillay bark extract, and Soapbark extract. Quillaia contains high concentrations of saponins that can be increased further by processing. Highly purified saponins from quillaia are used as adjuvants to enhance the effectiveness of vaccines. Other compounds in the crude extract include tannins and other polyphenols, and calcium oxalate.
QS-21 is a purified plant extract used as a vaccine adjuvant. It is derived from the soap bark tree, which is native to the countries of Chile, Peru, and Bolivia. The crude drug is imported from Peru and Chile.
Quillaja saponaria, the soap bark tree or soapbark, is an evergreen tree in the family Quillajaceae, native to warm temperate central Chile. In Chile it occurs from 32 to 40° South Latitude approximately and at up to 2000 m (6500 ft) above sea level. It can grow to 15–20 m (50–65 ft) in height. The tree has thick, dark bark; smooth, leathery, shiny, oval evergreen leaves 3–5 cm long; white star-shaped flowers 15 mm diameter borne in dense corymbs; and a dry fruit with five follicles each containing 10–20 seeds. The tree has several practical and commercial uses.
Phytochemistry is the study of phytochemicals, which are chemicals derived from plants. Phytochemists strive to describe the structures of the large number of secondary metabolites found in plants, the functions of these compounds in human and plant biology, and the biosynthesis of these compounds. Plants synthesize phytochemicals for many reasons, including to protect themselves against insect attacks and plant diseases. The compounds found in plants are of many kinds, but most can be grouped into four major biosynthetic classes: alkaloids, phenylpropanoids, polyketides, and terpenoids.
An aglycone is the chemical compound remaining after the glycosyl group on a glycoside is replaced by a hydrogen atom. For example, the aglycone of a cardiac glycoside would be a steroid molecule.
Indigenous ice cream, also known as sxusem, is a Canadian whipped confection made from soapberries and other various fruits; it has been eaten as a traditional dessert by many First Nations peoples. It has been suggested that it was first produced in the Interior Salish territory of British Columbia which was located in the upper basins of the Columbia and Fraser rivers, and included tribes such as the Columbia, Lillooet, and Shuswap among others.
Triterpenes are a class of terpenes composed of six isoprene units with the molecular formula C30H48; they may also be thought of as consisting of three terpene units. Animals, plants and fungi all produce triterpenes, including squalene, the precursor to all steroids.
Phytotoxins are substances that are poisonous or toxic to the growth of plants. Phytotoxic substances may result from human activity, as with herbicides, or they may be produced by plants, by microorganisms, or by naturally occurring chemical reactions.
Daigremontianin is a bufadienolide. Bufadienolides are steroids and cardiac glycoside aglycones that are similar to cardenolides, differing only in the structure of the C-17 substituent on the D ring. This chemical has been found to be toxic in experiments on mice. It is one of five bufadienolides that have been isolated from Kalanchoe daigremontiana.
A cardenolide is a type of steroid. Many plants contain derivatives, collectively known as cardenolides, including many in the form of cardenolide glycosides (cardenolides that contain structural groups derived from sugars). Cardenolide glycosides are often toxic; specifically, they are heart-arresting. Cardenolides are toxic to animals through inhibition of the enzyme Na+/K+‐ATPase, which is responsible for maintaining the sodium and potassium ion gradients across the cell membranes.
Ginsenosides or panaxosides are a class of natural product steroid glycosides and triterpene saponins. Compounds in this family are found almost exclusively in the plant genus Panax (ginseng), which has a long history of use in traditional medicine that has led to the study of pharmacological effects of ginseng compounds. As a class, ginsenosides exhibit a large variety of subtle and difficult-to-characterize biological effects when studied in isolation.
Quillaja is a genus of flowering plants, the only extant genus in the family Quillajaceae with two or three known species. It was once thought to be in the rose family, Rosaceae, but recent research shows it belongs in its own family. The inner bark of the soap bark tree contains saponin, which is a natural soap. Members of this genus are trees that grow to about 25 metres (82 ft).
Immune stimulating complexes (ISCOMs) are spherical open cage-like structures (typically 40 nm in diameter) that are spontaneously formed when mixing together cholesterol, phospholipids and Quillaja saponins under a specific stoichiometry. The complex displays immune stimulating properties and is thus mainly used as a vaccine adjuvant in order to induce a stronger immune response and longer protection. A specific adjuvant based on ISCOM technology is Matrix-M.
Prymnesin-2 is an organic compound that is secreted by the haptophyte Prymnesium parvum. It belongs to the prymnesin family and has potent hemolytic and ichthyotoxic properties. In a purified form it appears as a pale yellow solid. P. parvum is responsible for red harmful algal blooms worldwide, causing massive fish killings. When these algal blooms occur, this compound poses a threat to the local fishing industry. This is especially true for brackish water, as the compound can reach critical concentrations more easily.
Periplocin is a plant-derived glycoside whereby the sugar moiety is linked to a steroid. It can be extracted from cortex periplocae (CPP), the dry root of Periploca sepium.
