Secondary metabolites, also known as specialized metabolites, are organic compounds produced by any life form, such as bacteria, fungi, animals, or plants, which are not directly involved in the normal growth, development, and reproduction of the organism. These compounds are usually produced in response to stress and are not essential to the life of the producing organism but rather required for interaction with their environment. Secondary metabolites are commonly used by humans as medicines, flavorings, pigments, and recreational drugs.

Secondary metabolites serve various functions, including:

• Protection: Secondary metabolites protect the producing organism from pathogens, pests, and predators.
• Competition: Secondary metabolites mediate antagonistic interactions, such as competition and predation, as well as mutualistic ones such as pollination and resource mutualisms.
• Symbiosis: Secondary metabolites act as agents of symbiosis between microbes and plants, nematodes, insects, and higher animals.
• Differentiation: Secondary metabolites act as differentiation effectors.

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 rather required for interaction of plants with their environment and produced in response to stress. The three main classes of secondary metabolites in plants are terpenoids, phenolics, and alkaloids.