Secondary metabolites of Plants

Secondary metabolites are chemical compounds produced only by certain organisms (mostly plant) and in certain circumstances (each species / genus produces a set of metabolites of its own). Having a very important role in the well-being of the organism that produces it, for example, the level of biotic stresses for protection against herbivores and the abiotic level in response to environmental changes.

Among the various types of secondary metabolites are, for example, those containing nitrogen in the ring, such as Alkaloids; those composed mainly of carbon and hydrogen, such as terpenoids; and the phenolic compounds, which contain at least one aromatic ring and a hydroxyl group. 

Alkaloids 

can be derived from a variety of sources, such as lysine, ornithine, tyrosine, and tryptophan. Depending on the origin, several types of alkaloids are formed: Quinoleic alkaloids such as quinine, Pyridine alkaloids like nicotine, and isoquinoleic alkaloids such as morphine. 

Terpenoids 

can be synthesized from Acetyl CoA and consist of sets of isoprenes (5 Carbons). There are several types, such as monoterpenes such as limonene containing 2 isoprenes (10 carbons); diterpenes (4 isoprenes), such as vitamin A; and tretaterpenes (8 isoprenes), in the case of carotenoids. 

Phenolic compounds,

 however, arise from both the xiquimic acid and mevalonic acid pathways. Some examples of these compounds are vanillin and cinnamic aldehyde.