Polyphenols types

The most prominent wood adhesives used over the last quarter of a century have been aminoplast and polyphenolic types (2). In the United States, polyphenolic adhesives continue to be predominantly used for production of weather-resistant wood products, such as structural plywoods and flake boards (3). Phenolic resin prices have increased over the past decade, generally paralleling phenol prices. This increase has occurred in part due to a continuing erosion of United States phenol manufacturing capacity and the corresponding increase in availability of phenol from other countries. Any significant increase in the price of oil (the source of phenol) itself or interruption in supply will only compound the problem and raise phenol prices even higher. 

Anderson RA, Broadhurst CL, Polansky MM, Schmidt WF, Khan A, Flanagan VP, Schoene NW, Graves DJ. 2004. Isolation and characterization of polyphenol type-A polymers from cinnamon with insulin-like biological activity. J Agric Food Chem 52 65-70. 

The actual explanation was given as a result of marty years of research. The pH of 4-6 in the vacuoles of plants would be consistent with the colorless pseudobase form of anthocyanins or a little bit of the violet anl drobase. This pseudobase, on the other hand, is understood to be rare in Nature. In addition to pH, the interactions of anthocyanins with each other, other polyphenol type pigments (such as flavonoids or flavons), and metal ions such as alirminum, gallium and iron(in) collectively determine the color. Desert bluebells Phacelia campanularia) are true to their name as their flowers are blue, which is caused by aggregation between phacelianin molecules and their interaction with aluminum(III) and iron(III) ions. 

In the production of opalescent or natural-type apple juice, ascorbic acid is added to the fmit pulp before pressing, or to the juice as it comes from the press, to retain more of the apple flavor (4). Ascorbic acid addition and pasteurization of the juice as soon as possible after pressing prevent polyphenol oxidation, which causes browning and contributes to pulp flocculation. 

Diabetic patients have reduced antioxidant defences and suffer from an increased risk of free radical-mediated diseases such as coronary heart disease. EC has a pronounced insulin-like effect on erythrocyte membrane-bound acetylcholinesterase in type II diabetic patients (Rizvi and Zaid, 2001). Tea polyphenols were shown to possess anti-diabetic activity and to be effective both in the prevention and treatment of diabetes (Choi et al, 1998 Yang et al, 1999). The main mechanism by which tea polyphenols appear to lower serum glucose levels is via the inhibition of the activity of the starch digesting enzyme, amylase. Tea inhibits both salivary and intestinal amylase, so that starch is broken down more slowly and the rise in serum glucose is thus reduced. In addition, tea may affect the intestinal absorption of glucose. 

Phloem powder is rich in different types of fibers, lignans and polyphenols (Table 14.1). Phloem contains 58 g of fiber per 100 g, of which 51 g is insoluble and a lesser amount ( 7 g) is water-soluble. The total amount of different lignans in phloem is 79.3 mg/100 g, consisting mainly (98%) of secoisolariciresinol. The main flavonoids in phloem are catechins, and the... 

There has been some evidence of a higher antioxidant effect when both flavonoids and a-tocopherol are present in systems like LDL, low-density lipoproteins (Jia et al., 1998 Zhu et al, 1999). LDL will incorporate a-tocopherol, while flavonoids will be present on the outside in the aqueous surroundings. A similar distribution is to be expected for oil-in-water emulsion type foods. In the aqueous environment, the rate of the inhibition reaction for the flavonoid is low due to hydrogen bonding and the flavonoid will not behave as a chain-breaking antioxidant. Likewise, in beer, none of the polyphenols present in barley showed any protective effect on radical processes involved in beer staling, which is an oxidative process (Andersen et al, 2000). The polyphenols have, however, been found to act synergistically... 

Polyphenols are ubiquitous in all plant organs where they are found as monomers or in polymerised forms (Schofield et al, 2001). In addition to the beneficial effect of poljq)henols, they also bind minerals and precipitate proteins and carbohydrates, in effect reducing the nutritive value of foods. Polyphenols have been classified for nutritional purposes into extractable and non-extractable types (Bravo, 1998). Extractable polyphenols are low-and intermediate-weight phenolics while non-extractable polyphenols have high molecular weight and are insoluble in normal solvents. 

In recent years, numerous papers have been published about one of the most important groups of phytochemicals, the polyphenols (Manach and others 2004). These compounds, which possess an array of healthy properties, but also some disadvantages that will be discussed in this chapter, are present in a variety of plants used in both human and animal diets. However, the structure of this type of compound means that they can be oxidized by several pro-oxidant agents. The objective of this chapter is to describe the main enzymatic agents responsible for the degradation of polyphenols. In order to understand the mechanisms of degradation that will be described in the following sections, a brief summary of the main properties of the polyphenols is required. 

As regards their physiological roles, many polyphenols (because of their antimicrobial and antioxidant properties) are directly involved in the response of plants to various types of stress (Lopcz-Nicolas and others 2006 Lopez-Nicolas and Garcia-Carmona 2008). 

Because of the easily oxidizable structure of the polyphenols previously described, many studies have been published about the enzymatic degradation of these antioxidant compounds. This chapter exhaustively reviews the main publications concerning the degradation of this type of antioxidant compound by several enzymes. 

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