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In this article we will discuss about:- 1. Meaning of Secondary Metabolites 2. Role of Secondary Metabolites 3. Types.
Meaning of Secondary Metabolites:
Plants produce thousands types of chemicals. Some of the organic compounds like carbohydrates, fats, proteins, nucleic acids, chlorophylls, hemes are required for their basic metabolic processes and found throughout the plant kingdom. These organic compounds are called primary metabolites or biomolecules. These are produced in large quantities and can easily be extracted from the plants.
Many plants, fungi and microbes of certain genera and families synthesize a number of organic compounds which are not involved in primary metabolism (photosynthesis, respiration, and protein and lipid metabolism) and seem to have no direct function in growth and development of plants. Such compounds are called secondary metabolites (secondary plant products or natural products) (Table 9.7).
These compounds are accessary rather than central to the functioning of the plants in which they are found. These compounds are produced in small quantities and their extraction from the plant is difficult and expensive.
They accumulate in small quantities only in specific parts of plants. These are derivatives of primary metabolites. By the cultivation of plant cells in culture media, secondary metabolites can be produced on large scale.
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Role of Secondary Metabolites:
(1) Some of them attract animals for pollination and seed dispersal.
(2) They are used by the plants in their defence against herbivores and pathogens.
(3) They act as agents of plant-plant competition.
(4) They are used in making drugs, insecticides, flavours, pigments, scents, rubber, spices and other industrial materials like gums, resins for human welfare.
Types of Secondary Metabolites:
These secondary metabolites are highly numerous in number, chemically diverse in nature and belong to three groups.
1. Isoprenoids or Terpenes, e.g., rubber, steroids, essential oils, carotenoid pigments.
2. Nitrogen containing compounds, e.g., alkaloids, glucosinolates, glycosides, non-protein amino acids.
3. Phenolic compounds, e.g., lignin, tannins, coumarins, aflatoxins, flavonoids (anthocyanins).
