Polyphenol pathway reaction

Hardie, A. G., Dynes, J. I, Kozak, L. M., and R M. Huang. (2007). Influence of polyphenols on the integrated polyphenol-Maillard reaction humification pathway as catalyzed by birnessite. Annals Environ. Sci. 1, 91-110. 

Polyphenols can act as antioxidants by a number of potential pathways. The most important is likely to be by free radical scavenging, in which the polyphenol can break the radical chain reaction. Polyphenols are effective antioxidants in a wide range of chemical oxidation systems, being capable of scavenging peroxyl radicals, alkyl peroxyl radicals, superoxide, hydroxyl radicals, nitric oxide and peroxynitrate in aqueous and organic environments [121]. This activity is due to the ability of donating an H atom from an aromatic hydroxyl group to a free radical, and the major ability of an aromatic structure to support an unpaired electron by delocalization around the 7i-electron system. Phenolic acids... 

Jokic, A., Wang, M. C., Liu, C. Frenkel, A. I., and Huang, P. M. (2004b). Integration of the polyphenol and Maillard reactions into a unified abiotic pathway for humification in nature the role of 8-Mn02. Org. Geochem. 35, 747-762. 

S-adenosyl-L-methionine (SAM)-dependent methyl-ation was briefly discussed under Thiomethylation (see Figure 14). Other functional groups that are methylated by this mechanism include aliphatic and aromatic amines, N-heterocyclics, monophenols, and polyphenols. The most important enzymes involved in these methylation reactions with xenobiotics are catechol O-methyltransferase, histamine N-methylt-ransferase, and indolethylamine N-methyltransferase - each catalyzes the transfer of a methyl group from SAM to phenolic or amine substrates (O- and N-methyltransferases, respectively). Methylation is not a quantitatively important metabolic pathway for xenobiotics, but it is an important pathway in the intermediary metabolism of both N- and O-contain-ing catechol and amine endobiotics. 

Gossypol is a polyphenolic aldehydic compound, and it has been studied for its versatile biological activities. Gossypol s biological activities are based on direct chemical reactions, the inhibition of enzymes, and the regulation of signal transduction pathways. However, due to its toxicity, the application of gossypol is sometimes limited. 

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). 

---