Therapeutic Application Of Secondary Metabolites
“Necessity is the mother of invention” seems true, if we look at the plants, which being nonmotile and lacking immune system are not left helpless against a wide variety of biotic and abiotic stresses, instead wield an arsenal of chemicals to deter enemies, fend off pathogens, supersede competitors, and surpass environmental constraints. These chemicals were named “secondary metabolites” by A. Kossel in 1891, who described these organic compounds as incidentally occuring and not of paramount significance to plant life. A great majority of these compounds do not directly participate in growth, development and reproduction of plants hence named “secondary metabolites”. These compounds are deployed as taxonomic markers because of having limited distribution in taxonomic groups.
In constrast, primary metabolites include carbohydrates, acyl lipids, phyto-sterols and organic acids, which are found in all tissues of plants and perform metabolic activity necessity for growth and development of plants. There are no clear cut defined boundries between the two categories and both cannot be separated on the basis of their chemical structure, precursor molecules and biosynthetic origin e. g. amino acid proline is a primary metabolite while its C6 analogous molecule, pipecolic acid is alkaloid. Similarly diterpenes and triterpenes both classes contain primary and secondary metabolites these secondary metabolites are major contributors of specific odour, color and taste of plant parts. In the past these organic compounds were thought to be biologically insignificant and therefore plant biologist gave little attention to them. However, their chemical structures and properties were studied extensively by organic chemists since the 1850s.
It has now become evident that such believes were misleading and inaccurate and that secondary metabolites play an acitve and key role in potential defence mechanisms, especially in the chemical warfare between plants and their pathogens. Some of these compounds have also been elucidated to have role against herbivores and to attract pollinators, allelopathic agents, and protection against toxicity, UV-light sheilding and signal transduction. In view of their current prospective the term secondary metabolite seems inappropriate because it poses them as unimportant despite having a multidimensional role in plant life. From the last few decades secondary metabolites have got great attention due to their potential role in human nutrition, cosmetics, drugs and their indespensible role in plant defense.
This drastic change in interest of secondary metabolites is not purely academic but also of commercial nature. There commercial importance as dyes, drugs, polymers, waxes, glues, fibers, antibiotics, herbicides, insecticides also fueled the growing interest of secondary metabolites. The growing attention of their multidimensional role in plant and human life led to the reevaluation of their possible roles especially in ecological interactions.
