Polyphenol metabolism

Potential enzymes involved in anthocyanin metabolism — The lactase phlorizin hydrolase (LPH EC 3.2.1.108) present only in the small intestine on the outside of the brush border membrane and the cytosolic P-glucosidase (CBG EC 3.2.1.1) found in many tissues, particularly in liver, can catalyze the deglycosylation (or hydrolysis) of polyphenols. LPH may play a major role in polyphenol metabolism... 

Comparative Aspects of Polyphenol Metabolism - Proanthocyanidins and the complex esters of gallic and hexahydroxydiphenic acid show many structural similarities as plant metaijol i tes. The shape and size of the ester (5) is thus very similar to that of a proanthocyanidin hexamer (1, n = 4). The most striking feature of both structures however s the manner in which free phenolic groups are distributed over the surface of the molecule providing a structure with the inbuilt capacity for multidentate attachment to other species by hydrogen bonding. 

The cleavage of S-diketo acid is commonly seen in polyphenol metabolism and degradation such as orcinol (5-methylbenzene-l,3-diol) catabolism in Pseudomonas putida. Acetylpyruvate hydrolase (ca 38 kDa) is the terminal enzyme of orcinol catabolism, catalyzing the conversion of acetylpyruvate into acetate and pyruvate (equation 12). ... 

In order to elucidate polyphenol metabolic pathways, the primary site for metabolism needs to be addressed. The intestinal microllora will extensively metabolize (and even completely degrade) most compounds arriving in the colon however, early absorption from the gastrointestinal tract, in the stomach or small intestine, will result in a differing metabolite profile. Therefore, the mechanism of absorption of dietary polyphenols is inextricably linked to characterization of the resulting metabolites within the systemic circulation or individual tissues. 

The same research group [108], a year later, published an improved method for identifying and quantifying VOO phenolic compounds and their metabolites in human plasma by microelution SPE plate and liquid chromatography-tandem mass spectrometry. The pSPE-UHPLC-ESI-MS/MS method was fully validated and applied to analyze plasma samples collected after the ingestion of 30 mL of VOO in order to identify the studied phenolic compounds and their metabolites. These kinds of approaches are very important to achieve advances in the understanding of VOO polyphenols metabolism in order to explore and determine the mechanisms of action of VOO polyphenols and their role in disease prevention, to understand the factors that constrain their release from the VOO, it is very important to understand their extent of absorption, and their fate in the organism. 

Phenol-Explorer [27], Collected from more than 1300 scientific publications, Phenol-Explorer contains more than 500 different polyphenols in over 400 foods. In addition to online searching, the database is available for download. The current version includes data on polyphenol metabolism, as well as the effects on food processing and cooking. 

BRAVO L (1998) Polyphenols Chemistry, Dietary sources. Metabolism, and nutritional significance, Nutrition Reviews, 56, 317-33. 

Catechol-O-methyltransferase (COMT EC 2.1.1.6) is located in many tissues and catalyzes the methylation of polyphenols. The methylation is a well-established pathway in the metabolism of flavonoids such as those that undergo 3, 4 -dihydrox-ylation of ring B excreted as 3 -0-methyl ether metabohtes in rat bile. " Recently, the apparent methylation of both cyanidin-3-glucoside and cyanidin-3-sambubioside (cyanidin is an anthocyanin with a 3, 4 -dihydroxylation of ring B) to peonidin-3-glucoside and peonidin-3-sambubioside was reported in humans. In rats, this transformation occurred mainly in the liver and was catalyzed by COMT."°... 

Cerda B, Llorach R, Ceron JJ, Espin JC and Tomas-Barberan FA. 2003b. Evaluation of the bioavailability and metabolism in the rat of punicalagin, an antioxidant polyphenol from pomegranate juice. Eur J Nutr 42(1) 18—28. 

Higdon JV and Frei B. 2003. Tea catechins and polyphenols health effects, metabolism, and antioxidant functions. Crit Rev Food Sci Nutr 43(1) 89—143. Review. 

Polyphenol oxidase occurs within certain mammalian tissues as well as both lower (46,47) and higher (48-55) plants. In mammalian systems, the enzyme as tyrosinase (56) plays a significant role in melanin synthesis. The PPO complex of higher plants consists of a cresolase, a cate-cholase and a laccase. These copper metalloproteins catalyze the one and two electron oxidations of phenols to quinones at the expense of 02. Polyphenol oxidase also occurs in certain fungi where it is involved in the metabolism of certain tree-synthesized phenolic compounds that have been implicated in disease resistance, wound healing, and anti-nutrative modification of plant proteins to discourage herbivory (53,55). This protocol presents the Triton X-114-mediated solubilization of Vida faba chloroplast polyphenol oxidase as performed by Hutcheson and Buchanan (57). 

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