Grape phenolic compound

Grape phenolics compounds are important to wine colour, flavour, astringency and bitterness, with red wines generally containing 1200-1800 mg gallic acid equiv-alents/L of total phenolics, six- to ninefold more than present in white wines (Kennedy et al. 2006). Hydroxycinnamic acids (non-flavonoid phenolics) are major phenolic compounds of white wines and are responsible for their colour. Other non-flavonoid phenolics contribute flavour, such as vanillin, vinyl phenols and gallic acid. Vinyl and ethyl phenols, which can be present to variable extents, elicit phenolics, medical, Bandaid , barnyard and spicy characters in wine, which are generally... 

Family Red grape Phenolic compound (mg/kg fw) White grape (mg/kg fw) References... 

The study of red grape phenolic compounds requires the manual separation of the skins from the seeds of about 200 berries taken at random in the sampling. Once separated, the skins and the seeds are dried and lyophilized to facilitate the extraction and the determination of their phenolic content. 

Temperature also has an influence on the composition of grape phenolic compounds. Intensely colored wines are known to be difficult to obtain in extreme temperature conditions (too low or high) though the phenomenon involved can at first appear paradoxical. High temperatures stimulate metabolic reactions, whereas low temperatures curb migration. In either case, however, this corresponds with poor grape sugar alimentation and thus increased competition between primary... 

Similarly, fluctuations in grape phenolic content from one vintage to another and for a given variety are less than the variations between varieties. The genotypic effect of the variety is thus preponderant on grape phenolic compound richness. Anthocyanidic and procyanidic profiles vary... 

Laccase transforms the principal white grape phenolic compounds (cafeic and p-coumaric acids—both free forms and forms esterified by tartaric acid) into quinones (Salgues et al., 1986). These quinones tend to polymerize, forming brown compounds. These compounds are most likely responsible for the characteristic chocolate color of pourris pleins grapes. 

If grapes have low anthocyanin and tannin concentrations, only light red wines should be made. These wines, however, should be fresh and fruity. A limited concentration of grape phenolic compounds nevertheless merits an explanation. It can be a varietal characteristic, which must be taken into account. Vine cultivation conditions, favoring crop yields over quality, can also be responsible. 

A number of handbooks and monographs are available with detailed descriptions of a variety of plant products and their use (Shahidi and Naczk, 1995). From a more practical point of view, an interlaboratory comparison between six university and industry laboratories of 17 extracts of spices, teas, coffees, and grape skin and of tomato peel slurry established within the framework of an EU sponsored programme, would be of interest (Schwarz et al, 2001). In this collaboration, detailed chemical analysis of the content of different phenolic compounds is compared with six antioxidant assays for the 17 extracts including different extraction procedures. 

Hong, V. and Wrolstad, R.E., Use of HPLC separation/photodiode array detection for characterization of anthocyanins, J. Agric. Food Chem., 38, 708, 1990. Osmianski, J. and Lee, C.Y., Isolation and HPLC determination of phenolic compounds in red grapes. Am. J. Enol. Vitic., 41, 204, 1990. 

Kampa et al. made the interesting observation that protocatechuic acid, which is found in grapes and red wine from Vitis vimfera (Vitaceae), showed a time- and dose-dependent inhibitory effect on cell growth of T47D human breast cancer cells at low concentrations (108). The phenolic compound is a potent inhibitor of topoisomerase I (109). The plant likely contains some germanacrolides because these sesquiterpenes are known... 

The consumption of a mixture of phenolic compounds presented in apple or purple grape juice inhibited mammary carcinogenesis in 7,12-dimethylbenzo[a]anthracene (DMBA) treated rats (Liu and others 2005 Jung and others 2006). However, the individual antioxidants of these foods studied in clinical trials, including (3-carotene, vitamin C, and vitamin E, do not appear to have consistent preventive effects comparable to the observed health benefits of diets rich in fruits and vegetables, suggesting that natural phytochemicals in fresh fruits and vegetables could be more effective than a dietary supplement. 

Grapes and berries are rich sources of phytochemicals including phenolic compounds, pigments, and ascorbic acid. 

Murga R, Sanz MT, Beltran S and Cabezas JL. 2002. Solubility of some phenolic compounds contained in grape seeds in supercritical carbon dioxide. J Supercrit Fluids 23(2) 113-121. 

Revilla E and Ryan JM. 2000. Analysis of several phenolic compounds with potential antioxidant properties in grape extracts and wines by high-performance liquid chromatography—photodiode array detection without sample preparation. J Chromatogr 881(1-2) 461 169. 

Vatai T, Skerget M and Eljko Knez Z. 2009. Extraction of phenolic compounds from elder berry and different grape marc varieties using organic solvents and/or supercritical carbon dioxide. J Food Eng 90(2) 246-254. 

Polyphenols and flavonoids present in red wine and grape juice, fruits and vegetables, have potent antioxidant activity, which may slow down oxidative modification of LDL, and their subsequent toxicity (Wedworth and Lynch, 1995). Phenolic compounds exert cytoprotection on vascular cultured cells by inhibiting the calcium rise and subsequent oxidized LDL-mediated cell death (Vieira et al, 1998). These compounds may play a role in the relatively low level of coronary heart disease in Prance ( Fnench Paradox ) and other Mediterranean countries (Renaud and Ruf, 1994). 

Methods used for the detection of PAs in cmde or partially purified extracts can also be adapted for post-column analysis after fractionation (see below). Direct quantitative analysis of PAs in crude grape phenolic extracts is often impossible due to the complex sample matrix. Thus, fractionation or purification is often necessary before analysis. The Folin-Ciocalteu and Pmssian Blue assays are widely used for the quantification of total polyphenols in plants [27,28]. These methods are not specific for PAs due to the reaction of other phenolic compounds with these reagents. 

Pectinases and (3-glucanases are the only enzymes allowed in wine-making by European legislation. They are used as clarification and filtration agents and also to release aroma compounds that are mostly present in grape as nonvolatile glycosidic precursors. Pectolytic enzymes are also reported to increase extraction of phenolic compounds and wine color... 

Cheynier, V., Osse, C., and Rigaud, J., Oxidation of grape juice phenolic compounds in model solutions. J. Food Sci. 53, 1729, 1988. 

Es-Safi, N.E. et al., New phenolic compounds formed by evolution of (+)-catechin and glyoxylic acid in hydroalcoholic solution and their implication in color changes of grape-derived food. J. Agric. Food Chem. 48, 4233, 2000. 

Yanes and coworkers [43] demonstrated an application of IL for aqueous CE for fhe separation of phenolic compounds (flavonoids) found in grape seed exfracfs. By using [C Qlm] (n = 2,4) ILs as additives for the running electrolyte, a simple and reproducible electrophoretic method for the separation of polyphenols was developed. If was speculated that the separation mechanism was based on an association between the imidazolium cations and the polyphenols. The role of fhe alkyl substituents on the imidazolium cations was investigated and discussed [43]. The anion has little effect on the separation while a related study demonstrated that interaction between phenolic compounds and the IL cations in water occurred through n-n interactions. 

Alcohol consumption Moderate consumption of alcohol (for example, two drinks a day) decreases the risk of coronary heart disease, because there is a positive correlation between moderate alcohol consumption and the plasma concentration of HDLs. However, because of the potential dangers of alcohol abuse, health professionals are reluctant to recommend increased alcohol consumption to their patients. Red wine may provide cardioprotective benefits in addition to those resulting from its alcohol content, for example, red wine contains phenolic compounds that inhibit lipoprotein oxidation (see p. 233). [Note These antioxidants are also present in raisins and grape juice.]... 

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