Grape extracts

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. 

This chapter will provide a detailed account of the newly acquired data on flavonoid composition and distribution in grapes, and on flavonoid reactions in wine and structures of the resulting products. It will first present recent advances in analytical procedures that have rendered such progress possible and, for many of them, have been developed on grape extracts before being more widely applied to other plant material. Finally, it will review briefly current knowledge on the properties associated with flavonoids and their derivatives in wine. 

Figure 11.3.12 HPLC chromatograms of polyphenolics in Concord grape extract detected at 280 nm. (A) All polyphenolics, including anthocyanins. (B) Nonanthocyanin polyphenolics after fractionation. Peak identification 1, cis-caftaric acid 2, frans-caftaric acid 3, procyanidin B3 4, c/s-coutaric acid 5, frans-coutaric acid 6, epicatechin 7, quercetin galactoside 8, quercetin glucoside. Reproduced from Oszmianski and Lee (1990) with permission from the American Society for Enology and Viticulture.

Coombe showed that the activity of grape extracts was much greater on d-5 dwarf corn than on d-1 (13). Two different compounds have been isolated from bean seeds—bean factor 1 behaved like GA but bean factor II was ten times as active on d-5 as on d-1 (24, 45). Coombe believed that the activity in grapes may be due in part to the presence of bean factor II or other gibberellin-like compounds. 

Giinata, Z., Bayonove, C., Baumes, R., Cordonnier, R. (1985b). The aroma of grapes. Extraction and determination of free and glycosidically bound fractions of some grape aroma components. J. Chromatogr., 9, 83-90. 

Where are some superfruits and extracts that are under current medical research located within the research pyramid In the abbreviated list of fruits and extracts that follows, you can readily see that some superfruits—a< af berries, blueberries, and strawberries—are still in basic research within the bottom half of the pyramid (ten-plus years from qualifying for human research requirements), whereas other superfruits—cranberries, red grapes, the grape extract resveratrol, and anthocyanins extracted from different fruits—are progressing through clinical research within step 4. 

Grape seeds are rich in polyphenols, especially flavanols (catechin, epicatechin) and gallic acid (Meyer et al., 1997). When grape extracts are prepared after crushing of the seeds, increased levels of phenols are obtained compared with extracts prepared with intact grape seeds. In particular, flavan-3-ol levels increased significantly. The antioxidant activity, as measured by the ability to inhibit LDL oxidation, also increased when the seeds were crushed prior to extraction. 

Sample Preparation for Analysis of HCTA and Flavonols in Grape Extracts and Juice... 

Figure 4.5 Chromatogram of a wine sample containing OTA 4.41 xg/L (left) and a grape extract naturally OTA-contaminated at 4.92 pg/L (right). Emission spectra are recorded in the wavelength range 350-550 nm, the maximum is at 470 nm (Tonus et al., 2005)...

Figure 4.6 OTA analysis of the wine sample (left) and grape extract sample (right) reported in Figure 4.5 before (above) and after (below) synthesis of the methyl ester (Tonus et al., 2005)...

Recently, by performing direct nano-LC/ESI-MS sample injection onto a reverse phase capillary without immunoaffinity clean-up, LOD and LOQ in grape extracts of 1 and 2 pg/g, respectively, were reported (Timperio et al., 2006). HPLC analysis was carried out at flow 200nL/min and introducing l xL sample onto the column. Figure 4.9 shows a nano-LC/ESI-MS chromatogram recorded in positive mode in the analysis of acetonitrile solutions containing various concentrations of OTA. 

Recently, a LC/MS method to determine OTA in wine and grape extracts by using Surface-Activated-Chemical-Ionization and multistage fragmentation mass spectrometry (LC/SACI-MS3), was proposed (Flamini et al., 2007). SACI is an ionization source developed to analyze medium-high polar compounds in a wide range of m/z ratios (100-4000 Da). This device, used in determination of compounds such as... 

The grape extract or the wine is then purified by using a dispersive aminopropyl solid-phase extraction. These extraction techniques allow the removal of unwanted substances from grapes and wine such us sugars, organic acids, and other substances interfering in the pesticide quantitation (Anastassiades et al., 2003). 

Figure 8.3 HPLC-DAD separation of sulphur in grape extract. The analytical conditions are reported in Table 8.6...

Rhodes, P.L., Mitchell, J.W., Wilson, M.W., and Melton, L.D. 2006. Antilisterial activity of grape juice and grape extracts derived from Vitis vinifera variety Ribier. International Journal of Food Microbiology 107 281-286. 

Table I. Distribution of odor response in fractions obtained from C18, polyamide and PVP chromatographic separations of p-damascenone precursor from Concord grape extracts.

More recently, headspace and HS-SPME-GC/MS approaches for analysis of aroma in must and grape extracts were also proposed (Lopez et al., 2004 Prosen et al., 2007 Sanchez-Palomo et al., 2005 Rosillo et al., 1999). 

A satisfying method of sample preparation for GC/MS analysis of grape extract and used in several studies (Mateo et al., 1997 Chassagne et al., 2000 Flamini et al., 2001 2006), was proposed by Williams et al. (1982) and Di Stefano (1991). Skins of 100 berries are separated from the pulp and are extracted with 35 mL of methanol for 4h in the dark. Pulp and juice are reunited in a glass containing lOOmg of sodium metabisulfite. 

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