What are iridoids?

Iridoids are a class of phytonutrients characterised by their strong, bitter taste, developed by plants as a powerful line of defence against herbivorous animals.

Many of these plants have some common properties:

  •  they are well-known by the local inhabitants
  •  they have been used since many hundred / thousand years in traditional/folk medicine
  •  they usually they can tolerate harsh conditions (mechanical impacts, droughts etc.)
  •  they have few side effects (if any) when ingested
  •  they are widespread (many grow as weeds).

Medicinal plants are those that have been used traditionally to treat specific conditions and ailments, or to simply maintain or optimise health. Many of today’s pharmaceutical drugs have been inspired by the properties of medicinal plants. Iridoids are produced by medicinal plants as a defense mechanism against animals or against infection by microorganisms that threaten their livelihood (1-3).
Just like a human being has thousands of different cellular and hormonal activities occurring at any given time to attempt to adapt to our foods, drinks, air, stress, etc., medicinal plants have the same innate intelligence. They create these iridoids to fight off anything attempting to damage the plant. Imagine you were a fruit growing from a tree. If you had to endure bugs, weather, etc. you would learn to adapt and create defense mechanisms to survive those conditions. Iridoids are the plant’s response to the “stressful environment” that surounds them (4,5). From an evolutionary medicine point of view, this ability to adapt to their environment is the source of the adaptogenic properties by iridoids, i.e. when humans or animals consume iridoids they “feel better”. This “feel good” factor is based upon a number of healthful properties possessed by iridoids and iridoid-containing plants.

Although iridoids are relatively new to science, it is already known that they share some characteristics with other plant-sourced compounds like flavonoids or polyphenols, e.g. they all have strong antioxidant properties. Perhaps one of the most interesting facts that is being explored in laboratories worldwide, is the fact that one single plant can contain more than one iridoid, and that combinations of iridoids, as well as combinations of iridoids and other phytonutrients, such as antioxidant flavonoids and polyphenols , tend to work in synergy, i.e. they “combine forces”, i.e. each of the contributing synergistically towards improving your health and wellbeing (6-10).


1. Effects of plant phenology, nutrients and herbivory on growth and defensive chemistry of plantain, Plantago lanceolata
Jarzomski, C.M., Stamp, N. E.; Bowers, M.D.
Oikos, 2000 88(2):371-379

2. Host plant influences on iridoid glycoside sequestration of generalist and specialist caterpillars
Lampert EC, Bowers MD.
J Chem Ecol. 2010 Oct;36(10):1101-4. Epub 2010 Aug 31.

3. Plant Defense Against Herbivores: Chemical Aspects
Mithöfer A, Boland W.  
Annual Review of Plant Biology 2012 Epub 2012 Feb 9

4. Drought stress increases iridoid glycosides biosynthesis in the roots of Scrophularia ningpoensis seedlings
Wang, D. H. Du, F. Liu, H. Y. Liang, Z. S.
Journal of Medicinal Plants Research 2010, 4(24):2691-2699

5. Intraspecific Variation in Plant Defense Alters Effects of Root Herbivores on Leaf Chemistry and Aboveground Herbivore Damage
Wurst, S., Van Dam, N., Monroy, F., Biere A., Van der Putten, W.
Journal of Chemical Ecology 2008, 34(10):1360-1367

6. Infusions and decoctions of mixed herbs used in folk medicine: synergism in antioxidant potential.
Guimarães R, Barros L, Carvalho AM, Ferreira IC.
Phytother Res. 2011 Aug;25(8):1209-14. doi: 10.1002/ptr.3366. Epub 2011 Feb 9.

7. The genetics of bitterness and pungency detection and its impact on phytonutrient evaluation.
des Gachons CP, Beauchamp GK, Breslin PA.
Ann N Y Acad Sci. 2009 Jul;1170:140-4.

8. Biological and pharmacological activities of iridoids: recent developments
Tundis R., Loizzo M., Menichini F., Statti G., Menichini F. 
Mini-Reviews in Medicinal Chemistry, 2008, 8(4):399-420

9. Anti-Inflammatory Iridoids of Botanical Origin.
Viljoen A, Mncwangi N, Vermaak I.
Curr Med Chem. 2012 Mar 13. [Epub ahead of print]

10. A Method To Predict Synergy Between Various Phytonutrients In Activation Of The Antioxidant Response Element, A Major System For Cancer Prevention: DP20-06 (2009)
Levy, Joseph; Sharoni, Yoav,
Annals of Nutrition & Metabolism 2009, 55 Sup 1:161


What are Iridoids?

Where are Iridoids found?

Benefits of iridoids