Iridoids

Naturally occurring substances formally derived from the (eponymous) substance iridodial and biogenetically classifiable as monoterpene derivatives.

In contrast to other monoterpenes, they are mostly present as water-soluble, frequently less stable iridoid gylcosides (glycosidically linked with glucose). After hydrolytic cleavage, the aglycones polymerize to blue or blue-black dyes which formerly earned them the name "pseudoindicanes".

The following structural types occur:

• C10-iridoids, mostly distributed as glycosides (e.g. loganin and verbanin).
• C9-iridoids; these include aucubin and harpagide, the active ingredient of devil's claw (see Harpagophyti radix of the official devil's claw root).
• Valepotriate
• Secoiridoids