isoprenoid

Definition: The isoprenoids (or terpenoids) are a large and diverse class of naturally-occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways.

Most are multicyclic structures that differ from one another not only in functional groups but also in their basic carbon skeletons.

These lipids can be found in all classes of living things, and are the largest group of natural products.

Structure

Terpenes are hydrocarbons resulting from the combination of several isoprene units.

Terpenoids can be thought of as modified terpenes, wherein methyl groups have been moved or removed, or oxygen atoms added. (Some authors use the term "terpene" more broadly, to include the terpenoids.)

In animals

The steroids and sterols in animals are biologically produced from terpenoid precursors.

Sometimes terpenoids are added to proteins, e.g., to enhance their attachment to the cell membrane; this is known as isoprenylation.

Many of these are substrates for plant Cytochrome P450.

In plants

Plant terpenoids are used extensively for their aromatic qualities. They play a role in traditional herbal remedies and are under investigation for antibacterial, antineoplastic, and other pharmaceutical functions.

Terpenoids contribute to the scent of eucalyptus, the flavors of cinnamon, cloves, and ginger, and the color of yellow flowers. Well-known terpenoids include citral, menthol, camphor, Salvinorin A in the plant Salvia divinorum, and the cannabinoids found in Cannabis.

Types

 triterpenoids
 sesquiterpenoids
 diterpenoids
 sesterterpenoids
 triterpenoids
 tetraterpenoids
 polyterpenoids

See also

 HMG-CoA reductase pathway (mevalonic acid pathway)