Gallic acid equivalents

Wine and by-products Cinnamic acid derivatives, anthocyanins and flavanols dominate (10 to 20 J,M gallic acid equivalents) Oil-in-water emulsion (dressing model) Red wine yields better protection, but phenols in white and rose wine seem more efficient on a molar basis Sanchez-Moreno et al., 2000... 

Phenol content (measured as gallic acid equivalents) increased initially in fresh-cut carrot treated with different sanitizers and later decreased in a different pattern for each treatment (Ruiz-Cruz and others 2007). Washing treatments significantly affected phenol content. Comparing sanitized shredded carrots with controls (unwashed and water washed), a sharp increase with a maximum value at days 3 and 6 (5.6 to 6 mg/ 100 g) was found, followed by a decline. Final phenol concentration was 0.7 to 1.3 mg/ 100 g for all treatments at the end of the storage period (Ruiz-Cruz and others 2007). 

Total phenols are expressed as gallic acid equivalents (GAEs). Reprinted with permission from M. Lopez et al. [193]. 

Singleton and Esau (I) reviewed the methods for phenol analysis of wine. They pointed out that study would be greatly advanced if one could determine the total content of phenolic substances and express it in such a way that analysis of subclasses of phenols could be related to the original total and a balance sheet could be obtained. One could then say, for example, this wine has a total phenolic content of 1200 mg/liter calculated as gallic acid, and of that total, cinnamic acid derivatives account for 200 mg/liter, anthocyanins for 300 mg/liter, other small flavonoids for 200 mg/liter, and condensed tannins complete the total with 500 mg/liter of gallic acid equivalent. To accomplish this, the total phenol analysis not only must meet ordinary criteria of reproducibility and precision, but it also must be based on chemical relationships such that fractions determined separately can be converted to units of the total. Of course when clearcut fractionation can be accomplished by... 

Mg/liter GAE by calculation gallic acid equivalent (GAE) calculated from the differences in molecular weight and molar absorptivity in the assay (C). 

Because a single substance is used, the result must be reported as a response equivalent to the amount or concentration of that substance. As wine is analyzed on a concentration basis, the result is reported in gallic acid equivalents (GAE) using units of mg/liter. For any standard, the results must always be reported on an equivalent basis to avoid the perception that one is measuring the amount of the standard substance. 

For blanks one can use ethanol, water or methanol, whichever the tissue extract was dissolved in last. Since this is a spectrophotometric assay, it is important to have a standard curve to relate the absorbance value to a concentration. Common compounds used to generate a standard curve are chlorogenic acid (1.18) or gallic acid (1.5). The concentration of phenolic compounds is then reported as chlorogenic acid or gallic acid equivalents, respectively. 

A third method relies on the precipitation of proanthocyanidins with formaldehyde. First, the total phenolic content is measured using the Folin-Ciocalteu reagent as described before. A 0.5 mole equivalent of phloroglucinol (1.3) is added for every gallic acid equivalent in the extract. To 2 mL of this plant extract and phloroglucinol is added 1 mL of a 2 5 HC1 /H20 solution and 1 mL of an aqueous solution of formaldehyde (13 mL of 37% formaldehyde diluted to 100 mL in water). After an overnight incubation at room temperature, the unprecipitated phenols are estimated in the supematent by the Folin-Ciocalteu method. The precipitate contains the proanthocyanidins and the known amount of phloroglucinol, which is always quantitatively precipitated. 

Figure 8.5 Pomegranate by-product (PBP) consumption by E° mice attenuates atherosclerotic lesion development, in association with reduction in macrophage oxidative stress and Ox-LDL uptake. E° mice consumed PBP (17 or 51.5 mg gallic acid equivalents/kilogram/day) for 3 months. Control mice received only water (placebo). At the end of the study, the mice aortas as well as the mice peritoneal macrophages were harvested. (A) Atherosclerotic lesion size determination. (B) Total macrophage peroxide levels were determined by the DCFH-DH assay. (C) For determination of macrophage paraoxonase 2 (PON2) lactonase activity, cells (2 x 10e) were incubated with 1 mmol/L dihydrocoumarin in Tris buffer, and the hydrolysis rate was determined after 10 min of incubation at 25°C. (D) The extent of Ox-LDL (25 pg of protein/ milliliter, labeled with FITC) uptake by the mice macrophages (1 x 10e) was determined by flow cytometry. Results are expressed as mean S.D. of three different determinations. = p < 0.01 versus placebo.

The phenolic antioxidant activity in the corn oil emulsions of 17 selected Spanish wines and two Californian wines was examined for their preventive capability for lipid oxidation as dietary antioxidants. The inhibition of hydroperoxide formation [measured as percent of control for 10 iM gallic acid equivalents (GAE)] was increased from 8.4 to 40.2% in the presence of the red wines, from 20.9 to 45.8% with the rose wines, and from 6.5 to 47.0% with the white wines. The inhibition of hydroperoxide formation at 20 xM GAE was increased from 11.9 to 34.1% in the presence of red wines, from 0.1 to 34.5% with the rose wines, and from 3.3 to 37.2% with the white wines. The inhibition of the hexanal formation at 10 (jlM GAE was increased from 23.6 to 64.4% in the presence of red wines, from 42.7 to 68.5% with the rose wines, and from 28.4 to 68.8% with the white wines. Moreover, the inhibition of the hexanal formation at 20 xM GAE was increased from 33.0 to 46.3% in the presence of red wines, from 11.3 to 66.5% with the rose wines, and from - 16.7 to + 21.0% with the white wines. The antioxidant effect declined apparently with increasing concentration. The antioxidant activity might be ascribed to the five main groups of phenolics identified in the wines benzoic acids, anthocyanins, flavan-3-ols, flavonols, and hexanal [38]. 

The Folin-Ciocalteau analysis of total phenols was performed using the method of Singleton and Rossi (35). This procedure used Folin Ciocalteau s reagent (Sigma) and a saturated aqueous sodium carbonate solution to produce an absorbance at 765 nm. Gallic acid was used to make the standard curve and results are expressed as gallic acid equivalents (GAE). 

Total Phenolics (as Gallic Acid Equivalents, GAEs) in Selected Grapes and Berries... 

In recent decades, the extracts of leaves, seeds and roots of M. oleifera have been extensively studied for many potential uses including wound healing (31, 139, 140). The uses of the plants in wound healing are rationalised on the basis of their antioxidant capacity (52). M. peregrina has been shown to inhibit the DPPH radical at 89-93%, after 15 min of incubation at a test concentration of 50 pg/mL. M. peregrina has been shown to have total antioxidant capacity as gallic acid equivalent of 814 mg/g of ethanol extracts in the phosphomolybdenum assay. 

The moringa extracts (100 mg dry powder/25 ml water) were sonicated for 25 minutes. The total phenols were measured using the Folin Ciocalteu reagent and absorbance was measured at 752 nm. The results were expressed as grams of Gallic acid equivalents on a dry basis (g gallic acid/100 g DW) (7). 

NOTE g gallic acid equivalents/ lOOg dry weight g protein/100 g DW. weight g Trolox equivalents/lOOg dry ... 

Total phenolics, expressed as milligrams of gallic acid equivalents per gram (mg of GAE/g). nd, not detected, na, not available. 

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