Polyphenolics extraction

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. 

The platelet hist UIline release assay demonstrated that cotton mill dust extract, cotton bract extract, cotton leaf extract, dialyzed CMD extract, polyphenols, compound 48/80, rutin, trimethylamine HCl, quercetin, catechin, tannic acid, ellagic acid and sodium metasilicate all release histamine directly (48). Thus not only do tannin compounds induce histamine release, but they may also form higher molecular weight polymers and contain components that survive acid hydrolytic conditions (48). Tannins are widely distributed in the plant kingdom. 

Solvent evaporation should be done under reduced pressures at low temperatures to minimize the degradation of extracted polyphenolics. Due to the likely occurrence of hydrolysis, isomerization, and polymerization at higher temperatures, temperatures for the evaporation process should be maintained at 40°C or below. 

For an accurate quantification of phenolic compounds extracted from plant material, the starting plant material should be washed, dried, and weighed prior to extraction, and the amount of the final extract should be recorded. The extracted polyphenolics are generally diluted and then concentrated by evaporation of solvents. Evaporation should be performed at 30° to 40°C under reduced pressure. When extract-... 

Another method of extracting polyphenols from seeds and skins is by immersion of the fine powder, obtained by grinding the grape skins and seeds in liquid nitrogen, in an acetone/water 7 3 (v/v) solution containing 0.1% ascorbic acid added to prevent oxidation (Downey et al., 2003). 

Pedunculate oaks (Quercus robur or Quercus pedunculata) grow most widely in the Limousin. They are also present in Bourgogne, as well as the south of France. They have a high extractable polyphenol content and relatively low concentrations of odoriferous compounds. 

Weisburger, J.H. et al.. Effect of tea extracts, polyphenols, and epigallocatechin gallate on azoxymethane-induced colon cancer, Prac. Soc. Exp. Biol, Med., 217, 104, 1998. 

Montedorro, G., Bertuccioli, M., Anichini, F. (1978). Aroma analysis of virgin oil by head space (volatiles) and extraction (polyphenols) technique, in G. Charalambous and G.E. Inglett (eds.). Flavor of Foods and Beveridges Chemistry and Technology, Academic Press, New York, pp. 247-281. 

Similarly to other plant materials, grape pomace also contains a fraction of non-extractable polyphenols. 

Arranz, S Silvan, JM Saura-Calixto, F. Non extractable polyphenols, usually ignored, are the major part of dietary polyphenols a study on the Spanish diet. Molecular Nutrition and Food Research 2010, 54,1-13. 

The aqueous extract of summer savory was found to he anti-inflammatory against rhinosinusitis in rahhit at 250mg/kg. A hydroalcoholic extract, polyphenolic fraction, and the essential oil also displayed antinociceptive and anti-inflammatory effects when administered orally (50-2000 mg/kg) to mice and rats in different models of pain and inflammation. 

Sub- and supercritical fluid extraction with CO2 has several advantages. One is that CO2 is nontoxic, nonflammable, and noncorrosive. Also, the end product is obtained as a powder without the need for drying [197]. However, the relatively high equipment purchase and maintenance pose a major constraint. This technique has been successfully used to extract polyphenols from grape pomace, generally using CO2 modified with methanol [198-201] or ethanol as cosolvent [202]. 

Figure 8 illustrates one of the processing schemes used for separating various components in a hydrocarbon-containing plant. Acetone extraction removes the polyphenols, glycerides, and sterols, and benzene extraction removes the hydrocarbons. If the biomass species in question contain low concentrations of the nonhydrocarbon components, exclusive of the carbohydrate and protein fractions, direct extraction of the hydrocarbons with benzene or a similar solvent might be preferred. 

Chemical Antioxidant Systems. The antioxidant activity of tea extracts and tea polyphenols have been determined using in vitro model systems which are based on hydroxyl-, peroxyl-, superoxide-, hydrogen peroxide-, and oxygen-induced oxidation reactions (109—113). The effectiveness of purified tea polyphenols and cmde tea extracts as antioxidants against the autoxidation of fats has been studied using the standard Rancimat system, an assay based on air oxidation of fats or oils. A direct correlation between the antioxidant index of a tea extract and the concentration of epigallocatechin gallate in the extract was found (107). 

The total antioxidant activity of teas and tea polyphenols in aqueous phase oxidation reactions has been deterrnined using an assay based on oxidation of 2,2 -azinobis-(3-ethylbenzothiazoline-sulfonate) (ABTS) by peroxyl radicals (114—117). Black and green tea extracts (2500 ppm) were found to be 8—12 times more effective antioxidants than a 1-mAf solution of the water-soluble form of vitamin E, Trolox. The most potent antioxidants of the tea flavonoids were found to be epicatechin gallate and epigallocatechin gallate. A 1-mAf solution of these flavanols were found respectively to be 4.9 and 4.8 times more potent than a 1-mAf solution of Trolox in scavenging an ABT radical cation. 

Biological Antioxidant Models. Tea extracts, tea polyphenol fractions, and purified catechins have all been shown to be effective antioxidants in biologically-based model systems. A balance between oxidants and antioxidants is critical for maintenance of homeostasis. Imbalances between free radicals and antioxidants may be caused by an increased production of free radicals or decreased effectiveness of the antioxidants within the reaction system. These imbalances can be caused by the radicals overwhelming the antioxidants within the system, or by an excess of antioxidants leading to a prooxidant functionaHty (105—118). When antioxidant defense systems are consistently overwhelmed by oxidative reactions, significant damage can... 

Tea extracts and tea polyphenols inhibit copper- and peroxide-induced oxidation of LDL in vitro (116,123,124). The inhibitory concentration for 50% reduction (IC q) values for inhibition of copper-induced oxidation of LDL by some phenoHc antioxidants are Hsted in Table 7. The IC q for epigaHocatechin gaHate was found to be 0.075 p.mM, which was the most potent of all the phenoHc antioxidants tested (123,124). Similar results have been reported elsewhere (115,116,125,126). 

DETERMINATION OF POLYPHENOLIC ENANTIOMERS IN GREEN TEA EXTRACT BY CAPILLARY ZONE ELECTROPHORESIS... 

Many solid dosage forms made with green tea extracts can be seen in the market, and several are standardised to a content of polyphenols or catechins. 

J (1999) Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in hiunans , AmJ Clin Nutr, 70, 1040-45. 

J (2001) Green tea polyphenol extract attenuates inflammation in interleukin-2-deficient mice, a model of autoimmunity , J Nutr, 131 (7), 2034-9. 

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