Polyphenolics Phenolic acids Tannins

Phenolic acids Tannins Polyphenol oxidase, see Diphenol oxidases Polysaccharides cell wall... 

B. Polyphenols, hydroxycarboxylic acids, tannins and other phenol derivatives with fused rings (Table 164). 

Organophilic polyphenolic materials for oil-based drilling fluids have been described [407], The additives are prepared from a polyphenolic material and one or more phosphatides. The phosphatides are phosphoglycerides obtained from vegetable oils, preferably commercial lecithin. Humic acids, ligno-sulfonic acid, lignins, phenolic condensates, tannins the oxidized, sulfonated, or sulfomethylated derivatives of these polyphenolic materials may serve as polyphenolic materials. 

Polyphenolic materials prepared from a polyphenolic material (humic acids, lignosulfonic acid, lignins, phenolic condensates, tannins) and phosphatides (lecithin) - [407]... 

Polyphenols constitute one of the most and widely distributed groups of substances in the plant kingdom, with more than 8000 phenolic structures currently known. They can be divided into at least 10 different classes based upon their chemical structure, ranging from simple molecules, such as phenolic acids, to highly polymerized compounds, such as tannins. 

Polyphenolics are classified into three important groups phenolic acids, flavonoids, and tannins. Phenolic acids include hydroxyben-zoic (C6-Ci), hydroxyphenylacetic (C6-C2), and hydroxycinnamic (C6-C3) acids (Figure 11.2.3 also see Figure 11.3.3). Hydroxycinnamic acids are most widely distributed in plant tissues. The important hydroxycinnamic acids are p-coumaric, caffeic, ferulic, and sinapic... 

Chemical processing of bark is limited and the principal chemical products produced commercially from barks are based on the barks phenolic content (1,12). Barks generally are richer than wood in quantity and complexity of extractive components, the most important being a) the monomeric polyphenols or flavonoid compounds, and b) the polymeric phenolics, such as tannin, phloba-phenes and phenolic acids. 

Proteins react with polyphenols such as phenolic acids, flavonoids, and tannins, which occur widely in plant products. These reactions may result in the lowering of available lysine, protein digestibility, and biological value (Hurrell 1984). 

Among polyphenolic compounds, two types of flavonoids, the anthocyanins and flavanols (i.e., catechins, proanthocyanidins, condensed tannins), are particularly relevant to the quality of red wines, as they are key compounds for color definition and astringency. Other flavonoids such as flavonols may have some influence on color and bitterness, although they are present in red wines in much lower amounts. Phenolic acids and hydrolysable tannins, released from barrel wood, may also have an influence on wine taste and color, and hydroxycinnamoyl derivatives from grape must are involved in the oxidative browning of white wines together with flavanols. Besides, some of these perceptions may be modified by other sensory characteristics (e.g. sourness, sweetness) related to other wine components (Preys et al. 2006). 

Among the top twenty superfruits, seeds vary widely in size, number, texture, taste, and chewability. Those listed here have good crunch quality The seeds must be chewed to yield the nutrient payload and, for the most part, are tasteless. Some superfruit seeds, such as those in grapes, have a slightly bitter taste, which derives from the polyphenols (proanthocyanidins, tannins, and other phenolic acids) characteristic of the fruit. 

The tea bush and in particular its young leaves contain a high concentration of polyphenols and oxidative enzymes, thus the young leaves are better for tea manufacture. Tea polyphenols, previously called tea tannins, are also known as tea flavonoids. Among the polyphenols in fresh tea leaves, catechins are the predominant form of polyphenols, which account for 12-24% of the dry weight. Besides catechins, flavonol, and their glycosides, anthocyanidin and leucoanthocyanidin, phenolic acids and depsides are also present. Their typical concentrations are shown in table 8.1. These phenolic compounds are directly or indirectly associated with the characteristics of tea, including its color, taste, and aroma. 

A straightforward classification attempts to divide the broad category of phenolics into simple phenols and polyphenols, based exclusively on the number of phenol subunits present, but many plant phenolic compounds are polymerized into larger molecules. Thus, the term plant phenolics encompasses simple phenols, phenolic acids, coumarins, flavonoids, stilbenes, hydrolyzable and condensed tannins, lignans, and hgnins [4]. 

There are several ways in which phenols have been categorized. Harbome and Simmonds categorized polyphenols based on the number of carbon atoms, which includes simple phenols (Ce) phenolic acids and related compounds (Ce—Ci) acetophenones and phenyl acetic acids (Cg—C2) cinnamic acids, cinamyl aldehydes, and alcohols (Cg—C3) coumarins, isocoumarins, and chromones (Cg—C3) flavonoids (C15) biflavonyls (C30) stilbenes (Cg—C2—Cg) benzophenones and xanthones (Cg—C2—Cg) quinones (Cg, Cio, Cm) betacyanins (Cjg) and lignans, lignins, tannins, and phlobaphenes (which are dimmers, oligomers, or polymers) [19]. Polyphenols have also been categorized by some researchers based on their... 

Polyphenols are a widespread group of secondary metabolites found in plants derived from phenylalanine and tyrosine, and they are characterized by the presence of several phenol groups (i.e., aromatic rings with hydroxyls) [1]. Plant phenolics include simple phenols, phenolic acids (benzoic and cinnamic acid derivatives), coumarins, flavonoids, stilbenes, hydrolysable and condensed tannins, lignans, and lignins [2, 3]. 

The chemical nature of plant phenolics varies from simple molecules (phenolic acids) to complex polyphenols such as flavonoids, anthocyanins, and highly polymerized substances that include varying proportions of phenolic acids, phenyl propanoids, anthocyanins, and tannins, among others [3,16-18],... 

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