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NUTRITION & METABOLISM Plant phenolics and flavonoids
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Phenolics, possess an aromatic ring bearing one or more hydroxyl groups and their structures may range from that of a simple phenolic molecule to that of a complex high-molecular weight polymer, are widespread groups of substances in flowering plants, occurring in all vegetative organs, as well as in flowers and fruits, vegetables, cereals, grains, seeds and drinks. Despite this structural diversity, the groups of compounds are often referred to as “polyphenols”. PLANT PHENOLICS AND FLAVONOIDS
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Plant phenolics are secondary metabolites which are derived from pentose phosphate, shikimate, and phenylpropanoid, flavonoid, anthocyanin, and lignin pathways in plants. PLANT PHENOLICS AND FLAVONOIDS
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The shikimate pathway produces the aromatic amino acids, including phenylalanine, which can be further modified through the sequential of elongation and cyclization steps to form the flavonoids. In general, flavonoids are sub-classified into several families of fifteen-carbon molecules including flavonol, flavone, flavanone, flavan-3-ol, isoflavone, and anthocyanidin. PLANT PHENOLICS AND FLAVONOIDS
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As a first step, phenylalanine gets converted into coumaroyl-CoA by a number of enzymatic reactions. Then coumaroyl-CoA is converted into naringenin and onward, the pathway diverges forming flavanones, dihydroflavonols, leucoanthocyanins, anthocyanidins, and flavan-3-ols through a series of enzymatic steps. These molecules can produce a series of products, flavones and isoflavones, flavonols, anthocyanins, and proanthocyanidins (condensed tannins) existing in the forms of monomers, dimers, and polymers. Three main classes within these molecules are differing only in the extent of B-ring hydroxylation. ANR, anthocyanidin reductase; ANS, anthocyanidin synthase; DFR, dihydroflavonol 4-reductase; F3H, flavonoid- 3′ hydroxylase; FLS, flavonole synthase; FNS, flavone synthase; GT, glucosyltransferase; FLAVONOID PATHWAY IN PLANTS
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The multicellular algae that changed their marine environment to the harsh terrestrial had to face numerous challenges including: higher oxygen concentration, desiccation, increasing gravity, damaging heat and UV light, greater diurnal and seasonal fluctuations in temperatures, chances to be infected and eaten by new pathogens and grazers. In other words, plants had to overcome all of these challenges standing on the same place. Today, more than 500 million years later, we observe that not only all of these challenges were successfully overcome, but modern plants represent most evolutionally successful eukaryotic species colonizing all parts of our planet, between North and South poles. EVOLUTION AND PHYSIOLOGICAL FUNCTIONS OF FLAVONOIDS Flavonoids: a metabolic network mediating plants adaptation to their real estate Front Plant Sci. 2014; 5: 620. doi: 10.3389/fpls.2014.00620
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Along with the development of unique stem cells machinery, the evolution of plant-specialized secondary metabolites made plants safe, comfortable, and long-lived. (Some trees can live for 100s and
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