Terpenoids are dimers, or combinations of a 5 carbon precursor called isoprene. There are over 10,000 known types of terpenoids that range from 2 isoprene compounds called monoterpenes, to cartenoids with 8 isoprenes.

Monoterpenes- Monoterpenes are composed of 2 isoprenes. They are volatile essential oils such as citrue, citronella, limonene, menthol, camphor, and pinene. Commerical uses include their use in insect deterrent's ( candles, sprays) and in odor control ( think of all those lemony or 'oranage' smelling cleaning compounds).

Diterpenoids-Diterpenes are made of 3 to 4 isoprenes. They are widely distributed in latex ( white sticky stuff those oozes our of some plants when you break them open) and plant resins, some being rather toxic. It is diterpenes that make Rhododendron leaves poisonous. Gibberellin a plant hormone is a diterpene found in plants produced by plants to control growth.

Triterpenes-Triterpenes have 5 or more isoprenes. There are several different groups of triterpenes:

-Steroid hormones-This group includes the sterols which have 27-29 Carbon length chains. (An example is cholesterol). We always hear that plant fats don't contain cholesterol, but in fact a number do.
Another group of steroid hormones is the ecdysones which are used by insects for molting. Plant can interfere with the insect's lifecycle by producing and storing these compounds in their tissues.

-Vitamin D is another example of a triterpene which we prefer to consume.

Glycosides-These compounds are associated by most of us with treating the heart. In 1785, an English physician named Withering used extracts from Digitalis, commonly known as foxglove, as a remedy for heart disease. Monarch butterflies store the glycosides that they get from the leaves of milkweed in their wings to deter birds which feed on them. Most of these predators will spit out the bugs and avoid them all together after a couple of samples.

Saponins-Saponins are known to hemolyse blood cells. Needless to say these plants are dangerous eating for unsuspecting herbivores.

Tetraterpenes-Tetraterpenes include cartenoids, which we know better as carotenes and xanthophylls.

Polyterpenes-Polyterpenes are complex substances such as rubber.

Sesquiterpene lactones-A few of these substances are poisonous to farm animals while a number of them are cytotoxic, meaning that they have anti-tumor activity.


"Human hormones" in plants-There are a few hormones present in plants that are also found in humans. Hormones such as testosterone, androstenedione, and estrogen are found in small quantities in plants such as willows, apple seeds, beans, scotch pine, and golden rod.

In plants, these hormones:

Go to Phenol page or go back to the main defense page