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. Iridoids are typically found in plants as
glycosides, most often bound to
glucose
Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
.
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
Oleuropein is a glycosylation, glycosylated seco-iridoid, a type of polyphenol, phenolic bitter compound found in green olive skin, flesh, seeds, and leaves. The term oleuropein is derived from the botanical name of the olive tree, ''Olea europaea ...
and
amarogentin.
Occurrence
The iridoids produced by plants act primarily as a defense against herbivores or against infection by microorganisms. The
variable checkerspot butterfly also contains iridoids obtained through its diet which act as a defense against avian predators. 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. Iridoids are prevalent in the plant subclass
Asteridae, such as
Ericaceae
The Ericaceae () are a Family (biology), family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with about 4,250 known species spread acros ...
,
Loganiaceae,
Gentianaceae,
Rubiaceae
Rubiaceae () is a family (biology), family of flowering plants, commonly known as the coffee, madder, or bedstraw family. It consists of terrestrial trees, shrubs, lianas, or herbs that are recognizable by simple, opposite leaves with Petiole ( ...
,
Verbenaceae,
Lamiaceae
The Lamiaceae ( )
or Labiatae are a family (biology), family of flowering plants commonly known as the mint, deadnettle, or sage family. Many of the plants are aromatic in all parts and include widely used culinary herbs like basil (herb), ba ...
,
Oleaceae,
Plantaginaceae
Plantaginaceae, the plantain family or veronica family, is a large, diverse family (biology), family of flowering plants in the order Lamiales that includes common flowers such as Antirrhinum, snapdragon and Digitalis, foxglove. It is unrelated ...
,
Scrophulariaceae,
Valerianaceae, and
Menyanthaceae.
Iridoids have been the subject of research into their potential biological activities.
Biosynthesis
The iridoid ring scaffold is synthesized, in plants, by the enzyme iridoid synthase.
See also
* Deacetylasperulosidic acid, an iridoid compound found in a few medicinal plants, such as '' Morinda citrifolia''
References
Further reading
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