polyterpenoid

Polyterpenoid is a polymeric compound derived from terpenoid units. In most scientific contexts the term describes polymers whose repeating unit is a terpene monomer, most commonly isoprene (C5H8). The best-known natural polyterpenoids are polyisoprenoids such as natural rubber (cis-1,4-polyisoprene) and gutta-percha (trans-1,4-polyisoprene).

These materials occur in plants and some microorganisms; natural rubber is produced in the latex of rubber-producing plants, most notably Hevea brasiliensis, while gutta-percha is found in several tropical trees in the Sapotaceae family. Other polyterpenoids include polyprenols and polyprenyl phosphates, which function in biological membranes and in processes such as protein prenylation. Polyterpenoids can also be produced synthetically by polymerizing terpene monomers other than isoprene, yielding materials with varied backbones and properties.

Biosynthesis involves the condensation of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) units by prenyltransferase enzymes to form long polyisoprene chains, whose geometry (cis or trans) and molecular weight determine physical properties. Cis-1,4 polyisoprene tends to be elastic, as seen in natural rubber, whereas trans-1,4 polyisoprene is more rigid, as in gutta-percha. Industrially, synthetic polyisoprenes are produced by polymerizing isoprene for use in tires, gloves, and other latex products. Gutta-percha has historical applications in dental fillings and insulation.

The term polyterpenoid is somewhat historical; more precise terminology uses polyisoprenoid or terpene polymer. Classification is by monomer type (isoprene-based or other terpenes), stereochemistry, and molecular weight.