Secondary metabolite

Secondary metabolites, also called specialised metabolites, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, archaea, fungi, animals, or plants, which are not directly involved in the normal growth, development, or reproduction of the organism. Instead, they generally mediate ecological interactions, which may produce a selective advantage for the organism by increasing its survivability or fecundity. Specific secondary metabolites are often restricted to a narrow set of species within a phylogenetic group. Secondary metabolites often play an important role in plant defense against herbivory and other interspecies defenses. Humans use secondary metabolites as medicines, flavourings, pigments, and recreational drugs.

The term secondary metabolite was coined by Albrecht Kossel, the 1910 Nobel Prize laureate for medicine and physiology. 30 years later a Polish botanist Friedrich Czapek described secondary metabolites as end products of nitrogen metabolism.

Secondary metabolites commonly mediate antagonistic interactions, such as competition and predation, but also 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.