Polyphenols, naturally occurring

Capasso, R. 1997. The chemistry, biotechnology and ecotoxicology of the polyphenols naturally occurring in vegetable wastes. Curr. Top. Phytochem. 

Investigations have focused on the content of polyphenoHcs, tannins, and related compounds in various foods and the influence on nutrient availabiHty and protein digestibiHty. It has been estabHshed that naturally occurring concentrations of polyphenoloxidase and polyphenols in products such as mushrooms can result in reduced iron bio availabiHty (75). Likewise, several studies have focused on decreased protein digestibiHty caused by the tannins of common beans and rapeseed (canola) (76—78). 

Naturally occurring oxaarenes based on polycyclic pyrans encompass a plethora of structures including the plant polyphenols such as anthocyanins and a-tocopherol (vitamin E). Halogenated dibenzo-p-dioxins and dibenzofurans are formed both as by-products during the manufacture of chlorophenols, and from the incineration of organic matter in the presence of inorganic halides. 

Naturally occurring compounds such as phytochemicals, which possess anticar-cinogenic and other beneficial properties, are referred to as chemopreventers. One of the predominant mechanisms of their protective action is due to their antioxidant activity and the capacity to scavenge free radicals. Among the most investigated chemopreventers are some vitamins, plant polyphenols, and pigments such as carotenoids, chlorophylls, flavonoids, and betalains. Resolution of the potential protective roles of... 

A similar problem occurs with beer stabilization. A serious problem in the brewing industry is the tendency of some beers to develop hazes during long-term storage due to protein precipitation that is usually stimulated by small quantities of naturally occurring proanthocyanidin polyphenols. In the same way as observed for wine, the excess polyphenols are traditionally removed by treatment with insoluble PVPP, with the same resulting problems. To resolve the problems, several authors have proposed the use of laccase, which forms polyphenol complexes that may be removed by filtration or other separation means. 

Tannins are polyphenols that occur only in vascular plants such as leaves, needles, barks heartwood, seeds and flowers. Tannins exist primarily in condensed and hydrolysable forms. Natural tannin extracts have been employed since the turn of the last century in leather industry. Recent development of their industrial uses as adhesives, flocculants, depressants, viscosity modifier agents and more recently as corrosion inhibitors reflects their importance as industrial raw materials. Electrochemical studies have shown that tannins extracted from the barks of mangrove trees are excellent corrosion inhibitors of steel at very low pH. The mechanism of inhibition at this pH was due to the chemisorption of tannin molecules while at higher pH, inhibition was achieved via formation of ferric-tannates [6]. 

Mohammed. Naturally occurring polyphenol ic antioxidants modulate IgE-mediated mast cell activation. Immunology 2000 100(4) 471-480. NT043 Seredenin, S. B., V. N. Zhukov, M. G. 

Some naturally occurring catechols and polyphenols implicated in chemical defenses in plants. 

ABSTRACT Chlorogenic acids are polyphenolic compounds that occur ubiquitously in foods of plant origin. They are quinic acid esters of hydroxycinnamic acid. Recently, naturally occurring plant phenolics have attracted considerable attention in relation to their physiological potential. Depending upon the conditions, phenolic compounds can be either beneficial or detrimental to biological processes. 

Although sugars are found in juices, the high-intensity sweeteners are not. However, they are often used in juice-based drinks or nectars, and here it is important to ensure that there is resolution of the sweeteners of interest from the compounds naturally present in fruit juices. This can be a particular problem in drinks with a high juice content as naturally occurring polyphenolic materials in the juice can disturb the analysis. 

Naturally occurring organic matter exists in a wide variety of chemical forms. These range from the low molecular weight aliphatic acids, polyphenols, etc.,... 

PhIP. The inhibition by tea of these two tests, which are indicators of genotoxicity, suggests that naturally occurring plant extracts can modify metabolic activation of HAAs. Tea polyphenols, epigallocatechin gallate from green tea and theaflavin gal-late from black tea, display similar inhibiting action in both tests (see ref. 318). 

Teeth have a transparent outer layer of enamel which is about 2 mm thick, and an inner layer of white dentine which surrounds the innermost pulp cavity where the nerves are located. Both the enamel and the dentine are calcium phosphate, a mineral that can exist in various forms, that of the enamel layer being hydroxyapatite, which is one of the hardest naturally occurring minerals. When this is exposed to fluoride it forms an even harder mineral fluoroapatite. Unfortunately both this and hydroxyapatite are slightly porous and this is why teeth become stained by chemicals such as polyphenols and other dark coloured substances that are present in coffee, tea, red wine, bilberries, blueberries, and cigarette smoke. (Staining can also be caused by tetracycline antibiotics, especially when taken by children whose teeth are developing. This type of discoloration is permanent, which is why such antibiotics are now only prescribed for adults.)... 

The browning offruitisa common example of the oxidation of phenols to quinones. Apples, pears, potatoes, etc. contain polyphenol oxidase (PPO), an enzyme that catalyzes the oxidation of naturally occurring derivatives of catechol (benzene-1,2-diol) by atmospheric oxygen. The products are ortho-quinones, which are unstable and quickly condense to give brown polymers. 

The conversion of animal hides into leather by treatment with water-soluble plant extractives has been practiced since antiquity. This process became known as tanning and obviously involved the reaction of a naturally occurring extractive, tannin, with the protein in the hide. We now know, of course, that tannins comprise a whole spectrum of chemical compounds, but generally they are polyphenolic and polymeric. Tannins have been isolated from a wide variety of raw materials, including insect galls, fruit skins, seed hulls, leaves, bark, and heartwood. Indeed, tannins are of nearly ubiquitous occurrence in higher orders... 

This paper summarizes briefly the physicochemistry and enzymology of plant copper oxidases with particular emphasis on polyphenol oxidase and laccase. A brief comparative discussion of other naturally occurring copper proteins and artificial copper proteins is appropriate when discussing the physicochemistry of the copper site itself. In the case of the copper proteins listed in Table I, we know a great deal more about the copper site than about the physicochemistry of the rest of the protein molecule. This is primarily a result of the availability of sophisticated spectroscopic techniques such as optical spectroscopy (both absorption and circular dichroism) and electron spin resonance which are applicable to the electronic transitions of the copper ion. On the other hand, protein chemistry has progressed more slowly. Many of the proteins are large and complex multisubunit enzymes, difficult to purify, and often unstable. There are several excellent reviews on this group of proteins (59, 60, 61, 62). 

Many naturally occurring plant extracts are reputed to possess anti-irritant properties and have been recommended for use in cosmetic formulations. These include such diverse mixtures as tea tree oil, borage seed oil, Paraguay tea extract. Kola nut extract, oil of rosemary, and lavender oil. It is, however, difficult to standardize plant extracts and there may be a great deal of lot-to-lot variability in constituents. Understandably, this makes identification and isolation of any specific active constituent complex and laborious. The extracts may be oily or hydrophilic and contain compounds such as a-bisabolol, xanthines, polyphenols, and phytosterols.There is great potential in the use of plant extracts for irritation and sensitization reduction. This has been established within the cosmetic industry, and interest here has stimulated activity into reducing variability by more consistent cultivation techniques and more standardized extraction methods. 

Tannic acid is a naturally occurring plant polyphenol and can be found in practically all aerial plant tissues. 

Polyphenolic compounds occur widely distributed in nature and may possess a variety of interesting biological properties, e. g. antibiotic, antiviral and antitumor activity. The synthesis and further elaboration of these compounds often requires the selective protection or deprotection of specific phenolic hydroxy groups. To achieve this goal, the methods highlighted above for the various aliphatic polyols can also be applied successfully. 

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