Polyphenol chemical structure

Competitive inhibitors of GST Pl-1 fall under two categories non-glutathione-and glutathione-based compounds. The former group covers a broad range of chemical structures such as tricyclic-based dibenzazepines, polyphenolic natural products, alkaloids, pyrimethamine, and dyes. The latter group, as its name indicates, covers compounds whose main structure or backbone is that of GSH. 

Figure 1 Chemical structure of polyphenolics in citrus. (A) Bergamottin, (B) 6 7 dihydroxybergamottin, (C) Naringenin, (D) Naringin, (E) Rutin, (F) Tangeretin, and (G) Nobiletin.

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. 

Antarctic brown macroalgae are also reported to elaborate phlorotannins (polyphenolics)65 66 which, in several temperate and tropical phaeophytes,13 are known to have antifeedant effects. However, the chemical structure and the ecological role of phlorotannins in Antarctic brown macroalgae still remain to be established. 

The health benefits explain the growth in interest concerning the characterization and evaluation of phenolics and antioxidant capacity in food-related products. The chemical structures of the main polyphenols found in Madeira table wines are summarized in Fig. 7.13. 

FIGURE 7.13 Chemical structures of some polyphenols identified in Madeira wines. 

More recently, there has been a renewed recognition of the potential of bark-derived polyphenols for adhesives as a result of improved understanding of the chemical structure of these materials (, 5), new types of formulations (5), and the fact that tannins are being commercially used in adhesives in South Africa (7), thus serving as a prototype for utilization in other parts of the world. In order to properly assess the current developments in this field, this overview will provide a historical perspective on adhesives based on tannins as well as a summary of the extraction techniques and chemical structures. Finally, areas where additional work could be fruitful will be suggested. 

Figure 3.2 Chemical structures of major black tea polyphenols.

Figure 4.1 Chemical structures of the principal classes of polyphenols. The examples shown are of polyphenols with hydroxyl groups in the 7- and 4"-positions. Anthocyanins may also be found in oligomeric forms. The coumestane is coumestrol, The isoflavone (daidzein) differs from the flavonoid h the substitution of the phenolic group. For the flavonoid it is in the 2-position, whereas it is in the 3-position in the isoflavone.

Figure 6.1 Chemical structures of flavanoids including catechins and theaflavins. These tiavanoids consisted of two major groups flavanones, including naringenin, taxifolin, and fustin, and flavanols including green tea polyphenols (EC, ECG, EGC, EGCG), black tea polyphenols (TF-1, TF-2a, TF-2b, TF-3), and oolong tea polyphenol (TSA).

Figure 6.4 Chemical structures of carnosol, perillyl alcohol, and other polyphenols.

Polyphenols. Also called phenolic acids or phenolics, polyphenols are the parent class of several thousand compounds having similar chemical structure. Here is a list of the principal polyphenols to keep in mind for superfruits ... 

Typical of many members of the botanical plant family Solanaceae, which also includes the tomato, eggplant, and pepper, goji is phytochemically rich, characterized by having both major classes of pigments—carotenoids and polyphenols, identified in laboratory research as having antidisease mechanisms. Goji appears to be one of the richest plant sources of the carotenoid zeaxanthin (closely related in chemical structure to the... 

Grapes and berry fruits are rich sources of flavonoids and polyphenolics. Labor-intensive investigations over the years, initially from botanists and later from chemists and food scientists, provide a vast amount of knowledge about chemical structure, occurrence and stability of these compounds. As a consequence, food products, extracts, tinctures and dry powders are available with documented levels of flavonoids and other phenolics. 

Product stability and performance can be affected by exposure to several oxidative sources, including oxygen, free radicals, UV radiation, oxidative enzymes, catabolic oxidation, and chemical oxidation. Many antioxidants are also good UV absorbers due to their conjugated chemical structure. Typical antioxidants found in cosmetic products are flavonoids, polyphenols, carotenoids, thiols, tocopherol (vitamin E) and ascorbic acid (vitamin C) [71,72], According to Black [73], a combination of antioxidants from different classes is more effective than a single antioxidant due to an antioxidant cascade mechanism. 

The majority of the biological functions of teas may be attributed to their poly-phenolic components (see figures 9.1 and 9.2) the chemical structures of the main polyphenols isolated from green, black, oolong, and pu-erh teas are structurally related but not identical. The monomeric catechins from green tea may be considered the precursors of the more complex polyphenols found in other teas as a result of fermentation. 

As it can be deduced from the description of the chemical structures of anthocyans and anthocyanidins, polyphenolic pigments are usually water soluble (Figure 1). Noticeable exceptions are the curcumin oils (yellow),... 

Syntans. With the development of an understanding of the polyphenolic nature of vegetable tannins, and the increasing shortage of these naturally-occurring materials at the beginning of the twentieth century, efforts were made to synthesise products with related chemical structures in the hope that... 

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