Secondary metabolites, also known as natural products, are those products (chemical compounds) of metabolism that are not essential for normal growth, development or reproduction of the plant or organism. In this sense they are "secondary".
The function or importance of these compounds to the organism's development is usually of ecological nature as they are used as defence against predators (herbivores, pathogens etc.) for interspecific competition and to facilitate the reproductive processes.
Contrary to primary metabolites these compounds are not ubiquitous in the living organisms who produce them nor are they expressed continuously. Although plants are better known as a source of secondary metabolites also bacteria, fungi and many marine organisms (sponges, tunicates, corals, snails) are very interesting sources too.
The main classes of secondary metabolites are: alkaloids, terpenoids, aliphatic, aromatic and heteroaromatic organic acids, phenols, irridoids, steroids, volatile oils, resins and balsams, saponins.
List of most important secondary metabolites of plants:
- Class Alkaloids:
- Hyoscyamine, present in Datura stramonium
- Atropine, present in Atropa belladonna, Deadly nightshade
- Class Terpenoids:
- Azadirachtin A, present in Azadirachta indica, Neem tree
- Class Aliphatic, Aromatic and Heteroaromatic organic acids:
- Class Phenols:
- Resveratrol, present in Vine, Peanut
- Class Irridoids:
- Class Steroids:
- Class Volatile oils, Resins and Balsams:
- Class Saponins:
