Theories Polyphenol

A modification of the lignin theory of the formation of humic substances is the polyphenol theory, which considers the key interactions to be those between quinones, derived either from polyphenols or lignin, and amino compounds. 

In contrast to the selective preservation theory, the condensation pathway proposes that humic substances are derived from the polymerization and condensation of low-molecular-weight molecules that are products of the partial microbial degradation of organic residues (Kogel-Knabner, 1993). Under this scheme of increasing complexa-tion, fulvic acids would be the first humic substances synthesized, followed by humic acids and then humin (Stevenson, 1994). The two commonly accepted condensation models are the polyphenol theory and the sugar-amine or mela-noidin theory. 

Despite the current popularity of the polyphenol theory, a completely satisfactory scheme for the occurrence of humic and fulvic acids in diverse geologic environments has yet to be established. In practice, all pathways may be operative, but not to the same extent in all environments or in the same order of importance. A lignin pathway may-predominate in wet sediments, such as peats and swamps. The drastic conditions existing in soils under a harsh continental climate (e.g., some Mollisols) may favor humus synthesis by sugar-amine condensation. The disappearance of amino acids from buried sediments has been attributed to the formation of brown nitrogenous polyelectrolytes by reaction with reducing sugars (Stevenson, 1974). 

Caffeine contained in tea beverage is absorbed at about the same rate as caffeine in coffee, cola drinks, or in pure water. Data to support this conclusion was obtained in a human feeding experiment.109 The theory that complexation of caffeine with the polyphenolic material in tea retards absorption110-111 is not borne out. 

Toth GB, Pavia H (2006) Artificial wounding decreases plant biomass and shoot strength of the brown seaweed Ascophyllum nodosum (Fucales, Phaeophyceae). Mar Biol 148 1193-1199 Tugwell S, Branch GM (1989) Differential polyphenolic distribution among tissues in the kelps Ecklonia maxima, Laminaria pallida and Macrocystis angustifolia in relation to plant-defence theory. J Exp Mar Biol Ecol 129 219-230... 

Yates JL, Peckol P (1993) Effects of nutrient availability and herbivory on polyphenolics in the seaweed Fucus vesiculosus. Ecology 74 1757-1766 Zangerl AR, Bazzaz FA (1992) Theory and pattern in plant defense allocation. In Fritz RS, Simms EL (eds) Plant resistance to herbivores and pathogens. Chicago Press, Chicago, pp 363-391... 

Clausen TP, Reichardt PB, Bryant JP, Provenza FD. 1992. Condensed tannins in plant defense a perspective on classical theories. In Plant Polyphenols Synthesis, Properties, Significance. Hemingway RW, Laks PE, Editors. New York. Plenum, pp. 639-651. 

You probably know of this class of phytochemicals already, as polyphenols are the main reasons the superfruit industry started. For years, it was assumed that polyphenols are dietary antioxidants, but this role is now doubted by scientists. Instead, a new theory is that polyphenols have other important functions in promoting health, such as fine-tuning of enzymes, genes, receptors, and proteins, some of which may be the on-off switches for diseases—especially chronic inflammation thought to be common as an onset mediator of numerous diseases. 

Lobb, A., Mazzocchi, M., and Traill, B. (2007). Modelling risk perception and trust in food safety information within the theory of planned behaviour. Food Qual. Prefer. 18,384r-395. Lu, Y. and Foo, L. Y. (1999). The polyphenol constituents of grape pomace. Food Chem. 65, 1-8. 

An alternative or complimentary theory for the mode of action of simple phenolic compounds is that they are converted to much more toxic quinones. Pillinger et al. [69] found that various phenolic decomposition products of barley straw were most toxic under conditions favorable for oxidation of the compounds to quinones, and that quinones were up to one thousand-fold more toxic to algae than the parent compounds. The most likely route to conversion to a quinone is enzymatic. Peroxidases and polyphenol oxidases can perform such a reaction, depending on the substrate. However, polyphenol oxidase cannot be detected in most green algae [139] and has not been reported in cyanobacteria. 

Ti-awx-resveratrol is an especially important polyphenol derivative in wine from the viewpoint of anticancer effects. The chemical stracture of this compound resembles the hormone estradiol (Fig. 2.18). The substance in fact binds to estrogen receptors, it is sometimes called a phytoestrogen ( 3.24). However, resveratrol is much more important than its minor estrogen activity would make it appear. A very intensely studied— and also hotly debated—recent question is about the enhancement of the activity of an enzyme called sirtuirr Some researchers think that resveratrol increases this activity and helps preserve healthy cell functions. Some in vitro studies support this theory, but human clinical tests are still missing. Trans-... 

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