Iridoids are a class of secondary metabolites found in a wide variety of plants and in some animals. They are monoterpenes biosynthesized from isoprene and they are often intermediates in the biosynthesis of alkaloids. Chemically, the iridoids usually consist of a cyclopentane ring fused to a six-membered oxygen heterocycle, as exemplified by nepetalactone, the active ingredient in catnip. Cleavage of a bond in the cyclopentane ring gives rise to a subclass known as seco-iridoids. Iridoids are typically found in plants as glycosides, most often bound to glucose.
Iridoids are found in many medicinal plants and may be responsible for the some of their pharmaceutical activities. Isolated and purified, iridoids exhibit a wide range of bioactivities including cardiovascular, antipheptotoxic, chlorectic, hypoglycemic, anti-inflammatory, antispasmodic, antitumor, antiviral, immunomidulator and purgative activities.
The iridoids are produced by plants primarily as a defense against herbivores or against infection by microorganisms. To humans and other mammals, iridoids are often characterized by a deterrent bitter taste.
- Didna, B., Debnath, S., Harigaya, Y. "Naturally Occurring Iridoids. A Review, Part 1." Chem. Pharm. Bull. 55(2) 159-222 (2007).