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, immunomodulator 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.