Plant Secondary Metabolites

Four fifths of known natural products are of plant origin, either primary or secondary metabolites. Plant primary metabolites eg amino acids, sugars, fatty acids, vitamins are involved in plant metabolism, growth , maintenance and survival.

Plants also contain a group of chemicals called secondary metabolites. These are a group of chemically diverse natural products synthesised and stored only in plants, often peculiar to a few plant species and even parts of the plants, root, shoot , leaf or storage organ. Secondary metabolites are synthesised from a few key intermediates of primary metabolism and include non-protein amino acids, alkaloids, phenols and isoprenoids. Many have no immediately obvious function in cell growth and are produced by cells which have stopped dividing.

Secondary metabolites can be toxins or attractants to predators or potential pollinator, may have important hormonal and other roles in regulating plant physiological function. They have effects on the mammalian central nervous system and cardiovascular system of which plants have no obvious equivalent. Such metabolites include opium, cannabis, Plants contain a wide range of secondary metabolites, non protein amino acids, alkaloids, phenols and isoprenoids. Many of these have important biological effects when eaten by man. The benefits provided by fruit and vegetables may rely substantially on these secondary metabolites, though this is an uncharted field as yet.

Further Reading —

Aoyama Y, Noshiro M, Gotoh O, Imaoka S, Funae Y, Kurosawa N, Horiuchi T and Yoshida Y ( 1996) Sterol 14-demethylase P450 ( P45014DM ) is one of the most ancient and conserved P450 species. J Biochem 119 926-933
Doolitle RF, Feng D-F, Tsang S, Cho G, Little E ( 1996 ) Determining divergence times of the major kingdoms of living organisms with a protein clock Science 271 470-477
Eastwood MA ( 2001) a molecular biological basis for the nutritional and pharmacological benefits of dietary plants. Quarterly Journal of Medicine, 94, 45-48.
Fraenkel GS (1959)The raison d’etre of secondary plant substances Science 129 1466-1470
Harborne JB, Baxter H , Moss GP (1996) . Dictionary of Plant Toxins John Wiley Chichester
Herrlich P. Blattner C, Knebel A, Bender K, Rahmsdorf HJ. 91997) Nuclear and nonnuclear targets of genotoxic agents in the induction of gene expression. Shared principles in yeast, rodents , man and plants. Biol Chem 378, 1217-1229;
Lam H-M, Chiu J, Hsieh M-H, Meisel L, Oliveira IC, Shin M and Coruzzi G. ( 1998) Glutamate-receptor genes in plants. Nature 396, 125-126
Mann J , Davidson RS, Hobbs JB , Banthorpe DV and Harborne JB. Natural products. Their chemistry and biological significance.( 1994.) Addison Wesley Longman Ltd Harlow Esssex England.
Powis DA and Bunn SJ. Neurotransmitter release and its modulation. (1995). Cambridge University Press. Cambridge, England
Tugendreich S, Bassett DE, McKusick VA, Boguski MS and Hieter P ( 1991) Genes conserved in yeast and genes. Human Molecular Genetics 3 , 1509-1517,


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