Plants as sources of biomolecules for pharmaceutical drugs

    08-Jul-2021
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Jiten Sharma
Contd from previous issue
They play different roles within plants such as defence against soil micro-organisms, plant viruses and herbivorous animals, and in the process of reproduction by producing flowering pigmentswhich possess strong anti-oxidant potentials (carotenoids, phenolics and flavonoids), fruits having particular fragrances (terpenoid and phenolic compounds) for attracting pollinators, and involving insects/animals as dispersal agents thereby increasing the possibility for enlarging the number of individuals. In addition, secondary metabolites inhibit the growth of competitor plants and such compounds are often involved in key interactions between plants and their abiotic and biotic environments thus leading to evolutionary associations between particular groups of pests and plants. Secondary metabolites can be classified on the basis of their chemical structure, composition, solubility or the mechanism by which they are synthesized.
In chemical terms, these have been identified as phenolic and flavonoid compounds (8,000 compounds known) as terpenes and terpenoids (over 25,000 compounds) and alkaloids (around 12,000 types). The production of secondary metabolites is dependent on complex pathways derived from basic primary metabolites. The first step for secondary metabolite production involves the formation of specific enzymes which are involved in the transformation of primary metabolic products into secondary metabolites.
In the pathways for secondary metabolite production, processes of molecular oxidation occur. The oxidizing reactions are commonly catalysed by dioxygenases- enzymes which utilize oxygen and a-ketoglutarate. In addition to specific secondary metabolites, carbon dioxide and succinate are also released. Other steps of secondary metabolite biosynthesis require the methylation of potentially reactive carboxylic acid, amino and hydroxyl groups that can spontaneously interact and form products which are undesirable to the plant and then stored within the vacuoles. In many plants, the secondary metabolite contents are quite low although rich in the number of compounds. Depending upon requirement, large amount of molecules can be further obtained through chemical processes. (To be contd)