Iridoid

Last updated
Chemical structure of iridomyrmecin Iridomyrmecin.svg
Chemical structure of iridomyrmecin

Iridoids are a type of monoterpenoids in the general form of cyclopentanopyran, found in a wide variety of plants and some animals. They are biosynthetically derived from 8-oxogeranial. [1] Iridoids are typically found in plants as glycosides, most often bound to glucose.

Contents

The chemical structure is exemplified by iridomyrmecin, a defensive chemical produced by the ant genus Iridomyrmex , for which iridoids are named. Structurally, they are bicyclic cis-fused cyclopentane-pyrans. Cleavage of a bond in the cyclopentane ring gives rise to a subclass known as secoiridoids, such as oleuropein and amarogentin.

Occurrence

Aucubin skeletal.svg
Catalpol skeletal.svg
Aucubin and catalpol are two of the most common iridoids in the plant kingdom.

The iridoids produced by plants act primarily as a defense against herbivores or against infection by microorganisms.[ citation needed ] The variable checkerspot butterfly also contains iridoids obtained through its diet which act as a defense against avian predators. [2] To humans and other mammals, iridoids are often characterized by a deterrent bitter taste.

Aucubin and catalpol are two of the most common iridoids in the plant kingdom.[ citation needed ] Iridoids are prevalent in the plant subclass Asteridae, such as Ericaceae, Loganiaceae, Gentianaceae, Rubiaceae, Verbenaceae, Lamiaceae, Oleaceae, Plantaginaceae, Scrophulariaceae, Valerianaceae, and Menyanthaceae. [3]

Iridoids have been the subject of research into their potential biological activities. [3] [4]

Biosynthesis

The iridoid ring scaffold is synthesized, in plants, by the enzyme iridoid synthase. [5] In contrast with other monoterpene cyclases, iridoid synthase uses 8-oxogeranial as a substrate. The enzyme uses a two-step mechanism, with an initial NADPH-dependent reduction step followed by a cyclization step that occurs through either a Diels-Alder reaction or an intramolecular Michael addition. [5]

Loganic acid is an iridoid substrate converted to strictosidine which reacts with tryptamine, eventually leading to the indole alkaloids which include many biologically active compounds such as strychnine, yohimbine, vinca alkaloids, and ellipticine.

See also

Related Research Articles

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

Nepetalactone is a name for multiple iridoid analog stereoisomers. Nepetalactones are produced by Nepeta cataria (catnip) and many other plants belonging to the genus Nepeta, in which they protect these plants from herbivorous insects by functioning as insect repellents. They are also produced by many aphids, in which they are sex pheromones. Nepetalactones are cat attractants, and cause the behavioral effects that catnip induces in domestic cats. However, they affect visibly only about two thirds of adult cats. They produce similar behavioral effects in many other felids, especially in lions and jaguars. In 1941, the research group of Samuel M. McElvain was the first to determine the structures of nepetalactones and several related compounds.

<span class="mw-page-title-main">Cytochrome P450</span> Class of enzymes

Cytochromes P450 are a superfamily of enzymes containing heme as a cofactor that mostly, but not exclusively, function as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compounds, as well as for hormone synthesis and breakdown. In 1963, Estabrook, Cooper, and Rosenthal described the role of CYP as a catalyst in steroid hormone synthesis and drug metabolism. In plants, these proteins are important for the biosynthesis of defensive compounds, fatty acids, and hormones.

<span class="mw-page-title-main">Aminolevulinic acid synthase</span> Class of enzymes

Aminolevulinic acid synthase (ALA synthase, ALAS, or delta-aminolevulinic acid synthase) is an enzyme (EC 2.3.1.37) that catalyzes the synthesis of δ-aminolevulinic acid (ALA) the first common precursor in the biosynthesis of all tetrapyrroles such as hemes, cobalamins and chlorophylls. The reaction is as follows:

In molecular biology, biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism.

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

Chorismic acid, more commonly known as its anionic form chorismate, is an important biochemical intermediate in plants and microorganisms. It is a precursor for:

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

Voacangine is an alkaloid found predominantly in the root bark of the Voacanga africana tree, as well as in other plants such as Tabernanthe iboga, Tabernaemontana africana, Trachelospermum jasminoides, Tabernaemontana divaricata and Ervatamia yunnanensis. It is an iboga alkaloid which commonly serves as a precursor for the semi-synthesis of ibogaine. It has been demonstrated in animals to have similar anti-addictive properties to ibogaine itself. It also potentiates the effects of barbiturates. Under UV-A and UV-B light its crystals fluoresce blue-green, and it is soluble in ethanol.

<span class="mw-page-title-main">Bornyl diphosphate synthase</span>

In enzymology, bornyl diphosphate synthase (BPPS) (EC 5.5.1.8) is an enzyme that catalyzes the chemical reaction

Strictosidine synthase (EC 4.3.3.2) is an enzyme in alkaloid biosynthesis that catalyses the condensation of tryptamine with secologanin to form strictosidine in a formal Pictet–Spengler reaction:

<span class="mw-page-title-main">ATP citrate synthase</span> Class of enzymes

ATP citrate synthase (also ATP citrate lyase (ACLY)) is an enzyme that in animals represents an important step in fatty acid biosynthesis. By converting citrate to acetyl-CoA, the enzyme links carbohydrate metabolism, which yields citrate as an intermediate, with fatty acid biosynthesis, which consumes acetyl-CoA. In plants, ATP citrate lyase generates cytosolic acetyl-CoA precursors of thousands of specialized metabolites, including waxes, sterols, and polyketides.

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

Catalpol is an iridoid glucoside. This natural product falls in the class of iridoid glycosides, which are simply monoterpenes with a glucose molecule attached.

Cannabidiolic acid synthase is an enzyme with systematic name cannabigerolate:oxygen oxidoreductase . It is an oxidoreductase found in Cannabis sativa that catalyses the formation of cannabidiolate, a carboxylated precursor of cannabidiol.

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

Loganin is one of the best-known of the iridoid glycosides. It is named for the Loganiaceae, having first been isolated from the seeds of a member of that plant family, namely those of Strychnos nux-vomica. It also occurs in Alstonia boonei (Apocynaceae), a medicinal tree of West Africa and in the medicinal/entheogenic shrub Desfontainia spinosa (Columelliaceae) native to Central America and South America.

Curcumin synthase categorizes three enzyme isoforms, type III polyketide synthases (PKSs) present in the leaves and rhizome of the turmeric plant that synthesize curcumin. CURS1-3 are responsible for the hydrolysis of feruloyldiketide-CoA, previously produced in the curcuminoid pathway, and a decarboxylative condensation reaction that together comprise one of the final steps in the synthesis pathway for curcumin, demethoxycurcumin, and bisdemethoxycurcumin, the compounds that give turmeric both its distinctive yellow color, and traditional medical benefits. CURS should not be confused with Curcuminoid Synthase (CUS), which catalyzes the one-pot synthesis of bisdemethoxycurcumin in Oryza sativa.

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

Nepetalactol is an iridoid. It is produced from 8-oxogeranial by the enzyme iridoid synthase. Nepetalactol is a substrate for the enzyme iridoid oxidase (IO) which produces 7-deoxyloganetic acid. It has been identified in Actinidia polygama as a major cat attractant, and a mosquito repellent. The fact that mosquitos bite cats with nepetalactol on their fur less often may explain why cats are attracted to silver vine in the first place.

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

Iridodial is an iridoid. It is produced from 8-oxogeranial by the enzyme iridoid synthase (IS). Iridodial is one of the substrates for the enzyme iridoid oxidase (IO) which produces 7-deoxyloganetic acid.

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

Loganic acid is an iridoid. Loganic acid is synthesized from 7-deoxyloganic acid by the enzyme 7-deoxyloganic acid hydroxylase (7-DLH). It is a substrate for the enzyme loganate O-methyltransferase for the production of loganin.

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

Harpagoside is a natural product found in the plant Harpagophytum procumbens, also known as devil's claw. It is the active chemical constituent responsible for the medicinal properties of the plant, which have been used for centuries by the Khoisan people of southern Africa to treat diverse health disorders, including fever, diabetes, hypertension, and various blood related diseases.

<span class="mw-page-title-main">4-hydroxy-tetrahydrodipicolinate reductase</span> InterPro Family

In enzymology, a 4-hydroxy-tetrahydrodipicolinate reductase (EC 1.17.1.8) is an enzyme that catalyzes the chemical reaction

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

Salutaridinol is a modified benzyltetrahydroisoquinoline alkaloid with the formula C19H23NO4. It is produced in the secondary metabolism of the opium poppy Papaver somniferum (Papaveraceae) as an intermediate in the biosynthetic pathway that generates morphine. As an isoquinoline alkaloid, it is fundamentally derived from tyrosine as part of the shikimate pathway of secondary metabolism. Salutaridinol is a product of the enzyme salutaridine: NADPH 7-oxidoreductase and the substrate for the enzyme salutaridinol 7-O-acetyltransferase, which are two of the four enzymes in the morphine biosynthesis pathway that generates morphine from (R)-reticuline. Salutaridinol's unique position adjacent to two of the four enzymes in the morphine biosynthesis pathway gives it an important role in enzymatic, genetic, and synthetic biology studies of morphine biosynthesis. Salutaridinol levels are indicative of the flux through the morphine biosynthesis pathway and the efficacy of both salutaridine: NADPH 7-oxidoreductase and salutaridinol 7-O-acetyltransferase.

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

Furegrelate, also known as 5-(3-pyridinylmethyl)benzofurancarboxylic acid, is a chemical compound with thromboxane enzyme inhibiting properties that was originally developed by Pharmacia Corporation as a drug to treat arrhythmias, ischaemic heart disorders, and thrombosis but was discontinued. It is commercially available in the form furegrelate sodium salt.

References

  1. Gene discovery in the biosynthesis of medicinal alkaloids in Catharanthus roseus
  2. Bowers, M. Deane (March 1981). "Unpalatability as a Defense Strategy of Western Checkerspot Butterflies (Euphydryas scudder, Nymphalidae)". Evolution. 35 (2): 367–375. doi:10.2307/2407845. JSTOR   2407845. PMID   28563381.
  3. 1 2 Tundis, Rosa; Loizzo, Monica; Menichini, Federica; Statti, Giancarlo; Menichini, Francesco (2008). "Biological and Pharmacological Activities of Iridoids: Recent Developments". Mini-Reviews in Medicinal Chemistry. 8 (4): 399–420. doi:10.2174/138955708783955926.
  4. Dinda, Biswanath; Debnath, Sudhan; Harigaya, Yoshihiro (2007). "Naturally Occurring Iridoids. A Review, Part 1". Chemical & Pharmaceutical Bulletin. 55 (2): 159–222. doi: 10.1248/cpb.55.159 . PMID   17268091.
  5. 1 2 Geu-Flores, F.; Sherden, N. H.; Courdavault, V.; Burlat, V.; Glenn, W. S.; Wu, C.; Nims, E.; Cui, Y.; O'Connor, S. E. (2012). "An alternative route to cyclic terpenes by reductive cyclization in iridoid biosynthesis". Nature. 492 (7427): 138–142. Bibcode:2012Natur.492..138G. doi:10.1038/nature11692. PMID   23172143.

Further reading

Moreno-Escobar, Jorge A.; Alvarez, Laura; Rodrıguez-Lopez, Veronica; Marquina Bahena, Silvia (2 March 2013). "Cytotoxic glucosydic iridoids from Veronica Americana". Phytochemistry Letters. 6 (4): 610–613. doi:10.1016/j.phytol.2013.07.017.