Polyphenol free-radical scavenging antioxidants Polyphenolic compound

There are numerous other polyphenolic compounds possessing in vitro and in vivo antioxidative activity. Several examples of these compounds are cited below. One of nonflavonoid polyphenols of particular interest is resveratrol (3,5,4 -trihydroxy-Znmv-stilbcne, Figure 29.8), which has been identified as a potential cancer chemopreventive agent and an antimutagen [182]. It has been found that resveratrol is the efficient inhibitor of cyclooxygenase and the inhibitor of free radical-mediated cellular processes. For example, resveratrol is a better free radical scavenger than a-tocopherol or ascorbic acid but has nearly the same activity as... 

As polyphenolic compounds, flavonoids have the ability to act as antioxidants by a free radical scavenging mechanism [140, 141, 142], This involves the formation of less reactive flavonoid phenoxyl radicals (Eq 1 and 2) on the other hand, through their known ability to chelate transition metals [143,144], these compounds may inactivate iron ions, and bivalent... 

Details about structure, biosynthesis, and classification of phenolics are described in the other chapters in this handbook. Plant phenolics have a distinctive ability to form non-covalent, intermolecular complexes with each other and with both large and small molecules. Recognition of the antioxidant activities of many polyphenols has established correlation with the health benefits by such compounds [34]. This leads to the development of commercial products containing free-radical-scavenging phytochemical mixtures, for example, Pycnogenol (procyanidin extracted from Pinus maritima). Table 82.2 represents a list of polyphenolic compounds used in nutraceuticals and their biologic effects on human health. 

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... 

Antioxidants, such as tea polyphenols, curcumin, and, camosol, may be expected to work by increasing intracellular GSH or total 011018, scavenging free radicals, or iron chelations. Many of the compounds classified as antioxidants that have been shown to inhibit NFkB activation are phytopolyphenols that are good peroxidase inhibitors or substrates. Many are effective at concentration that may be too low to be compatible with a radical-scavenging role, and their effects might be better explained if they were acting on a more specific enzymatic process. 

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