Secondary metabolites are organic compounds produced by any lifeform, such as bacteria, fungi, animals, or plants, which are not directly involved in the normal growth, development, or reproduction of the organism. They are also called specialized metabolites, toxins, secondary products, or natural products. Secondary metabolites are useful natural products that are synthesized through secondary metabolism in plants. Humans use secondary metabolites as medicines, flavorings, pigments, and recreational drugs. The term "secondary metabolite" was first coined by Albrecht Kossel, the 1910 Nobel Prize laureate for medicine and physiology.
Secondary metabolites commonly mediate antagonistic interactions, such as competition and predation, as well as mutualistic ones such as pollination and resource mutualisms. Usually, secondary metabolites are confined to a specific lineage or even species, though there is considerable evidence that horizontal transfer across species or genera of entire pathways plays an important role in bacterial (and, likely, fungal) evolution.
Plants are capable of producing and synthesizing diverse groups of organic compounds and are divided into two major groups: primary and secondary metabolites. Secondary metabolites are metabolic intermediates or products that are not essential to the growth and life of the producing plants but are required for interaction of plants with their environment and produced in response to stress. Their antibiotic, antifungal, and antiviral properties protect the plant from pathogens. The three main classes of secondary metabolites in plants are terpenes, phenolics, and nitrogen-containing compounds.
In summary, secondary metabolites are organic compounds produced by any lifeform that are not directly involved in the normal growth, development, or reproduction of the organism. They are useful natural products that mediate antagonistic and mutualistic interactions and are used by humans as medicines, flavorings, pigments, and recreational drugs. In plants, secondary metabolites are produced in response to stress and protect the plant from pathogens.
