Chemical Nature of Triterpenoids:

Triterpenoids are C30 compounds which are prepared from six isoprene units. They are widely distributed in the plant kingdom. They are present in either free state or as esters or glycosides.

Classification of Triterepenoids:

They are further classified as

(i) Tetracyclic triterpenoids

(ii) Pentacyclic triterpenoids

Steroids are the degraded triterpenes. Triterpenes are commonly present in most of the dicotyledonous plants.

The plant families which produce triterpenoids are cucurbitaceae, caryophyllaceae, leguminosae, apocynaceae etc. Azadirachtin from Azadirachta indica is a prominent triterpenoid in the plant kingdom. Triterpenoids are also present in marine sources like squalene, ambrein and lanosterol from shark, ambergris and wool fat respectively. These are mostly the stress compounds (phytoalexins) produced by the plants in response to the environmental stress and ecological interaction.

Chemical Nature of Tetraterepnoids:

Tetraterpenoids are C40 compounds of terpenoid groups. They are biosynthetically prepared by tail-to-tail condensation of geranyl geraniol. They contain long sequence of conjugated double bonds. They are a prominent group of natural colouring matters which exhibit purple, yellow, red or orange colours. They are present in both plants and animals. In plants they act as photosynthetic accessory pigments and in animals they act as a source of vitamin A and as antioxidants.

  Terpenoids