Saponin

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Saponins (Latin "sapon", soap + "-in", one of) are bitter-tasting, usually toxic plant-derived secondary metabolites. They are organic chemicals and have a foamy quality when agitated in water and a high molecular weight. They are present in a wide range of plant species throughout the bark, leaves, stems, roots and flowers but particularly in soapwort (genus Saponaria ), a flowering plant, the soapbark tree ( Quillaja saponaria ), common corn-cockle ( Agrostemma githago L.), baby's breath (Gypsophila spp.) and soybeans ( Glycine max L.). They are used in soaps, medicines (e.g. drug adjuvants), fire extinguishers, dietary supplements, steroid synthesis, 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] [3]

Contents

Classification based on chemical structure

Structurally, they are glycosides with at least one glycosidic linkage between a sugar chain (glycone) and another non-sugar organic molecule (aglycone).[ citation needed ]

Steroid glycosides

Steroid glycosides are saponins with 27-C atoms. [4] They are modified triterpenoids where their aglycone is a steroid, these compounds typically consist of a steroid aglycone attached to one or more sugar molecules, which can have various biological activities. These compounds are known for their significant cytotoxic, neurotrophic and antibacterial properties. These may also be used for partial synthesis of sex hormones or steroids. [5] [1]

Triterpene glycosides

Triterpene glycosides, are natural glycosides present in various plants, herbs and sea cucumbers [6] and possess 30-C atoms. [4] These compounds consist of a triterpene aglycone attached to one or more sugar molecules. Triterpene glycosides exhibit a wide range of biological activities and pharmacological properties, making them valuable in traditional medicine and modern drug discovery. [1]

Uses

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. [7] Saponins have also been used as adjuvants in development of vaccines, [8] such as Quil A, an extract from the bark of Quillaja saponaria . [7] [9] This makes them of interest for possible use in subunit vaccines and vaccines directed against intracellular pathogens. [8] In their use as adjuvants for manufacturing vaccines, toxicity associated with sterol complexation remains a concern. [10]

Quillaja is toxic when consumed in large amounts, involving possible liver damage, gastric pain, diarrhea, or other adverse effects. [9] 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. [11]

Saponins are used for their effects on ammonia emissions in animal feeding. [12] In the United States, researchers are exploring the use of saponins derived from plants to control invasive worm species, including the jumping worm. [13] [14]

Decoction

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.

Biological sources

Saponins have historically been plant-derived, but they have also been isolated from marine organisms such as sea cucumber. [15] They derive their name from the soapwort plant (genus Saponaria , family Caryophyllaceae), the root of which was used historically as a soap. [1] [16] [2] In other representatives of this family, e.g. Agerostemma githago , Gypsophila spp., and Dianthus sp., saponins are also present in large quantities. [17] 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. [18] 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. [19] 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 [20] from root exudates and abiotic stresses, as nutritional deficiency. [21]

Role in plant ecology and impact on animal foraging

In plants, saponins may serve as anti-feedants, [2] 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. Some saponins are toxic to cold-blooded organisms and insects at particular concentrations. 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. [22]

Ethnobotany

Most saponins, which readily dissolve in water, are poisonous to fish. [23] 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. [24] [25] [26]

Although prohibited by law, fish-poison plants are still widely used by indigenous tribes in Guyana. [27]

On the Indian subcontinent, the Gondi people use poison-plant extracts in fishing. [28]

In 16th century, saponins-rich plant, Agrostemma githago, was used to treat ulcers, fistulas, and hemorrhages. [29]

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. [30]

Chemical structure

Chemical structure of solanine, a highly toxic alkaloid saponin found in the nightshade family. The lipophilic steroidal structure is the series of connected six- and five-atom rings at the right of the structure, while the hydrophilic chain of sugar units is to the left and below. Note the nitrogen atom in the steroid skeleton at right, indicating this compound is a glycoalkaloid. Solanine.svg
Chemical structure of solanine, a highly toxic alkaloid saponin found in the nightshade family. The lipophilic steroidal structure is the series of connected six- and five-atom rings at the right of the structure, while the hydrophilic chain of sugar units is to the left and below. Note the nitrogen atom in the steroid skeleton at right, indicating this compound is a glycoalkaloid.

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]

See also

Related Research Articles

<span class="mw-page-title-main">Cardiac glycoside</span> Class of organic compounds

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 include 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 and milkweed 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.

<span class="mw-page-title-main">Glycoside</span> Molecule in which a sugar is bound to another functional group

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.

<span class="mw-page-title-main">Squalene</span> Chemical compound

Squalene is an organic compound. It is a triterpene with the formula C30H50. It is a colourless oil, although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as Squalus is a genus of sharks). An estimated 12% of bodily squalene in humans is found in sebum. Squalene has a role in topical skin lubrication and protection.

<span class="mw-page-title-main">Quillaia</span> Natural bark extract used in food and medicine

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, Soapbark extract, and Quillajae cortex. 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.

<span class="mw-page-title-main">QS-21</span> Plant extract

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.

<i>Quillaja saponaria</i> Species of plant

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.

<span class="mw-page-title-main">Phytochemistry</span> Study of phytochemicals, which are chemicals derived from plants

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.

<span class="mw-page-title-main">Cerberin</span> Chemical compound

Cerberin is a type of cardiac glycoside, found in the seeds of the dicotyledonous angiosperm genus Cerbera; including the suicide tree and the sea mango. As a cardiac glycoside, cerberin disrupts the function of the heart by blocking its sodium and potassium ATPase. Cerberin can be used as a treatment for heart failure and arrhythmia.

<i>Agrostemma githago</i> Species of flowering plant in the carnation family Caryophyllaceae

Agrostemma githago, the common corn-cockle, is a herbaceous annual flowering plant a member of Caryophyllaceae, also called the pink family or the carnation family of plants. The name of this genus is derived from Greek: agros (αργοσ) “field” and stemma (στέμμα) “garland, crown."

<span class="mw-page-title-main">Aglycone</span> Chemical compound

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.

<span class="mw-page-title-main">Triterpene</span> Class of chemical compounds

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.

<span class="mw-page-title-main">Cardenolide</span> Chemical compound

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.

In immunology, an adjuvant is a substance that increases or modulates the immune response to a vaccine. The word "adjuvant" comes from the Latin word adiuvare, meaning to help or aid. "An immunologic adjuvant is defined as any substance that acts to accelerate, prolong, or enhance antigen-specific immune responses when used in combination with specific vaccine antigens."

<span class="mw-page-title-main">Ginsenoside</span> Class of steroids

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.

<span class="mw-page-title-main">Oleanolic acid</span> Pentacyclic chemical compound in plant leaves and fruit

Oleanolic acid or oleanic acid is a naturally occurring pentacyclic triterpenoid related to betulinic acid. It is widely distributed in food and plants where it exists as a free acid or as an aglycone of triterpenoid saponins.

<span class="mw-page-title-main">Tomatine</span> Chemical compound

Tomatine is a glycoalkaloid, found in the stems and leaves of tomato plants, and in the fruits at much lower concentrations. Chemically pure tomatine is a white crystalline solid at standard temperature and pressure.

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.

<i>Silene jenisseensis</i> Species of flowering plant

Silene jenisseensis, is a species of flowering plant in the family Caryophyllaceae, native to Siberia, Far East and Mongolia.

<span class="mw-page-title-main">Oleandrose</span> Chemical compound

Oleandrose is a type of carbohydrate with the chemical formula C7H14O4. With a six-carbon chain, it is classified as a hexose. With two hydroxyl groups replaced with hydrogen atoms, it is a dideoxy sugar. The hydroxyl group at C3 is methylated.

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