Polyphenolic natural compounds

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. 

The encapsulation of polyphenolics is generating a growing number of scientific papers, some of which are discussed in this chapter. The published studies show that the major obstacles to the use of these powerful natural compounds, that is, their limited stability, and their poor aqueous solubility limiting their bioavailability, can be overcome by encapsulation. Many innovative solutions are available, and have been shown to be effective in potentiating and protecting the action of polyphenolics. 

Polyphenols are a heterogeneous group of natural compounds, particularly known for their beneficial effects on human health. In nature, polyphenols are produced by the secondary metabolism of plants, where, in relation to their various chemical characteristics have different roles ... 

Fig. 5.1 Chemical structures reporting examples of natural compounds with different biological effects, a a-Linolenic acid, an essential omega-3 fatty acid. Omega-3 is known to decrease the risk of cardiovascular diseases b a-amantine is a deadly natural compound found in the Amanita phalloides mushrooms c resveratrol, a polyphenolic stilbenoid produced in plants with several reported pharmacological actions...

Com oil contains natural antioxidants such as tocols, carotenoids and polyphenols. These compounds prevent protein oxidation, lipid peroxidation (Figure 7) and reactive oxygen species formation. 

Investigations have focused on the content of polyphenoHcs, tannins, and related compounds in various foods and the influence on nutrient availabiHty and protein digestibiHty. It has been estabHshed that naturally occurring concentrations of polyphenoloxidase and polyphenols in products such as mushrooms can result in reduced iron bio availabiHty (75). Likewise, several studies have focused on decreased protein digestibiHty caused by the tannins of common beans and rapeseed (canola) (76—78). 

SRB contains high-quality protein, oil, dietary fiber, polysaccharides, fat-soluble phytochemicals (plant derived bioactive compounds) and other bran nutrients. Rice bran and germ are the richest natural sources of B complex vitamins as well as E vitamins, polyphenols, several antioxidants and minerals. It is now available in the commercial food ingredient market as a safe and effective functional food and dietary supplement. 

Phenolic acids and polyphenols are natural plant constituents which impart flavor and textural components to beverages made from these plants. In order to better understand the role of these easily oxidized compounds in the flavor and stability of beverages, it is necessary to determine them at the low concentrations they occur. LCEC has been shown to be quite effective at these trace determinations... 

Infrared Spectra. Limited effort has been made to identify the major chemical group components of the extract. Infrared spectra (Perkin-Elmer 913) of the evaporated extracts from two lakes were similar in having peaks at the following frequencies 3,000-3,100, 3,200-3,600, 1,500-1,650, and 1,690-1,760 cm-l. These preliminary data would suggest the presence of polyphenolic compounds in the extract which may be related to humic materials occurring in nature (16). 

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... 

Cervellati R, Renzulli C, Guerra MC and Speroni E. 2002. Evaluation of antioxidant activity of some natural polyphenolic compounds using the Briggs-Rauscher reaction method. J Agric Food Chem 50(26) 7504-7509. 

In addition to their possible prooxidant activity (see above) polyphenols and flavonoids may influence cancer cells via their antioxidant properties. Recently, Jang et al. [219] studied cancer chemopreventive activity of resveratrol, a natural polyphenolic compound derived from grapes (Chapter 29). These authors showed that resveratrol inhibited the development of preneoplastic lesions in carcinogen-treated mouse mammary glands in culture and inhibited tumorigenesis in a mouse skin cancer model. Flavonoids silymarin and silibinin also exhibited antitumor-promoting effects at the stage I tumor promotion in mouse skin [220] and manifested antiproliferative effects in rat prostate cancer cells [221]. 

Phase 1 clinical trials of the natural polyphenol quercetin (33) against several types of cancer have shown that this compound is well tolerated when administered at a dose of 70 mg/kg by i.v. bolus [63,64]. Further studies revealed that 33 inhibits GST Pl-1 completely after 2 h at a concentration of 25 pM however, addition of GSH partially restores activity. HPLC and LC-MS studies indicate that 33 inhibits GST Pl-1 through the formation of a covalent yet reversible bond with GST Pl-1 cysteine residue at position 47. 

Curcumin (16) is a polyphenolic compound derived naturally from the plant Curcuma longa also known as turmeric (Haldi). It is the primary source of the distinctive bright yellow color of the spice commonly used in the preparation of curries. Originating in India, turmeric was probably cultivated initially as a dye, and later used in cosmetics and foods. It has... 

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