Polyphenols, natural degradable

Many papers have been published about the enzymatic degradation of polyphenols through the action of oxidizing enzymes. Thus, various classifications have been provided for these types of biocatalytic molecules, according to their coenzyme requirements or according to the nature of the oxidizing substrate (the electron acceptor) and the reaction products (Fig. 4.1). 

Polyphenoloxidase (PPO, EC 1.14.18.1) is one of the most studied oxidative enzymes because it is involved in the biosynthesis of melanins in animals and in the browning of plants. The enzyme seems to be almost universally distributed in animals, plants, fungi, and bacteria (Sanchez-Ferrer and others 1995) and catalyzes two different reactions in which molecular oxygen is involved the o-hydroxylation of monophenols to o-diphenols (monophenolase activity) and the subsequent oxidation of 0-diphenols to o-quinones (diphenolase activity). Several studies have reported that this enzyme is involved in the degradation of natural phenols with complex structures, such as anthocyanins in strawberries and flavanols present in tea leaves. Several polyphenols... 

As its name suggests, supercritical fluid extraction (SEE) relies on the solubilizing properties of supercritical fluids. The lower viscosities and higher diffusion rates of supercritical fluids, when compared with those of liquids, make them ideal for the extraction of diffusion-controlled matrices, such as plant tissues. Advantages of the method are lower solvent consumption, controllable selectivity, and less thermal or chemical degradation than methods such as Soxhlet extraction. Numerous applications in the extraction of natural products have been reported, with supercritical carbon dioxide being the most widely used extraction solvent. However, to allow for the extraction of polar compounds such as flavonoids, polar solvents (like methanol) have to be added as modifiers. There is consequently a substantial reduction in selectivity. This explains why there are relatively few applications to polyphenols in the literature. Even with pressures of up to 689 bar and 20% modifier (usually methanol) in the extraction fluid, yields of polyphenolic compounds remain low, as shown for marigold Calendula officinalis, Asteraceae) and chamomile Matricaria recutita, Asteraceae). " ... 

Coir. Coir is a valuable and versatile fiber derived from the coconut husk. The best quality coir is produced from green coconut, which is more difficult to harvest and has a lower copra yield than more mature coconut. The amount of copra and the quantity of coir produced are inversely related (61). Husks must be retted to manufacture coir. This process involves holding the husks under water, away from air, with mud and leaves for a period of a few months to a year. Fermentation is accomplished by short rod bacteria such as Pseudomonas, Rerobacter, and Bacillus. The microbial process is a polyphenolic degradation in which the pectic substances are decomposed. Slow moving and slightly saline water in a natural source speeds the process and produces a better quality fiber (66). 

The surfaces of Mn oxides promote the oxidative polymerization of many polyphenolics, the polycondensation of pyrogallol and glycine, and the formation of humic substances. Many organics are oxidatively decomposed by Mn oxides during the reduction of Mn(III) or Mn(IV). The role of Mn oxides in C turnover and N transformations should, thus, be studied in depth. Besides natural organics, the kinetics of the degradation of certain xenobiotics by Mn oxides and oxyhydroxides in soils and related environments warrant investigation. 

The apparent source materials for forming such a hypothetical humic polymer would be lignin degradation products or plant polyphenols such as flavonoids. Because it has little relationship with the physical or chemical characteristics of actual humic materials, this type of model has fallen out of favor almost completely, except for ambiguous statements, still occasionally encountered, that the color of natural waters is due to tannins. ... 

Natural polyphenols like flavonoids or tannins possess a well-known protective effect towards oxidation, which can be used against pathologies in which free radicals are incriminated, like can-cer. " In cosmetic formulations, these antioxidant molecules are useful to protect the constitutive elements of skin, like collagen or elastin, against degradations or cross-linking reactions responsible for a decrease in elasticity and the appearance of wrinkles with ageing. ... 

The relation between oxidation of monophenols and polyphenols has been investigated extensively by Nelson and his students. The nature of the reactions studied is still not clear, but many interesting aspects have been explored. As in the case of other workers, it was found that there is a tendency for the ability to oxidize monophenols (cresolase) to be lost on purification, while polyphenol oxidation (catecholase) is more stable. The ratio of catecholase to cresolase activity of purified preparations appears to vary with electrophoretic mobility, and it has been suggested that a peptide component is lost from the enzyme, and that the purified preparations represent partially degraded enzyme. ... 

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