Phenolics assay

Total Phenols Assay (Folin-Ciocalteu Reagent)... 

As phenolics are well-known antioxidant agents, the Folin-Ciocalteau total phenolics assay was performed to assess phenolic content in ginseng roots. This assay was performed as described by Singleton et al. [20] with modifications [21]. Briefly, extract dissolved in 70% methanol was combined with Folin-Ciocalteau reagent, incubated for 5 min, and then 7.5% NaHCOs was added. Samples were transferred into microplate wells in triplicate, incubated in darkness for 2 h, and then absorbance read at 725 nm. Samples were blanked against a treatment with only solvent. A standard curve of quercetin was produced and data were expressed as quercetin equivalents. 

Correlation Between Total Phenols Expressed as Percent Caffeic Acid Equivalents and Ozone Injury. Twelve cultivars of peanuts ranging from low to high ozone sensitivity were examined. Foliage of each of the cultivars was evaluated for content of total phenols before and after ozone treatment. Because of the relatively high concentrations of caffeic acid in peanut foliage, values are expressed as percent caffeic equivalents in the total phenol assay. Experimental results used in establishing the correlation between caffeic acid and ozone injury are shown in Table I. 

Table II. Molar Absorptivity in the Total Phenol Assay and Precipitability with Acidic Formaldehyde ...

Amine and Aminophenol Derivatives. Amines and aminophenols (Table VIII) react with the F-C reagent about as predicted considering the aromatic amino groups equivalent to phenolic hydroxyls. This would be an important interference with total phenol assay in samples with appreciable aromatic amine content. Fortunately, for this and other reasons as well, the major wine grapes and most other fruit and vegetable products are free of significant concentrations of aromatic amines which would interfere. Correction might be made for methyl anthranilate... 

Phenol Assay Before and After Formaldehyde Treatment... 

Several reaction characteristics of gel-immobilized peroxidase, including activity and thermal stability, will be examined in this experiment. A spectrophoto-metric assay for peroxidase is introduced. The literature reports many assays for measurement of peroxidase activity. The aminoantipyrine-phenol assay is selected because it is rapid, convenient, and accurate and requires less toxic reagents than other assays. 

Upon analysis of the non-flavonoid fraction of wine, pyrimidines have been found (65MI307, 79AJEV98) by chromatography on Sep-hadex 6-25 and phenol assayed by colorimetry. Of the nucleic acids (mainly guanine 96 and xanthine 97) less than 5mg/L can be assumed to be present. 

Procyanidin contents are commonly determined using the more specific functional group assays. If purified extracts have to be analyzed, procedures determining phenolics in general may nevertheless be quite useful. A distinction between polyphenol and non-polyphenol "contents" can be made by performing a general phenolic assay before and after... 

The emission yield from the horseradish peroxidase (HRP)-catalyzed luminol oxidations can be kicreased as much as a thousandfold upon addition of substituted phenols, eg, -iodophenol, -phenylphenol, or 6-hydroxybenzothiazole (119). Enhanced chemiluminescence, as this phenomenon is termed, has been the basis for several very sensitive immunometric assays that surpass the sensitivity of radioassay (120) techniques and has also been developed for detection of nucleic acid probes ia dot-slot. Southern, and Northern blot formats (121). 

The cmde product formed from the alkylation of phenol with isoamylene contains principally 2-/ r2 -amylphenol, 4-/ r2 -amylphenol, and 2,4-di-/ r2 -amylphenol. 4-/ r2 Amylphenol is purified to its typical assay of 99+% by fractional distillation. 4-/ r2 -Amylphenol [80-46-6] is commercially available as a soHd, flaked material packaged ia paper or plastic bags (25 kg net weight) or as a molten material ia tank wagon or railcar quantities. 

A method for the estimation of the total alkaloids and of non-phenolic alkaloids (emetine fraction) is given in the British Pharmacopoeia, 1932, Addendum VI, which requires the drug to contain not less than 2 per cent, of alkaloids, of which at least 55 per cent, must be non-phenolic bases, calculated as emetine. The British Pharmacopoeia also gives an assay process for emetine in emetine bismuth iodide, the form in which the drug is chiefly used in medicine it is required to contain not less than 25 and not more than 28 per cent, of emetine. In the United States Pharmacopoeia, XIII, both Cephcelis Ipecacuanha and C. acuminata are recognised and must contain not less than 2 per cent, of ether-soluble alkaloids. 

More recently, the reaction advancement of resole syntheses (pH = 8 and 60°C) was monitored using high-performance liquid chromatography (HPLC), 13C NMR, and chemical assays.55,56 The disappearance of phenol and the appearances of various hydroxymethyl-substituted phenolic monomers and dimers have been measured. By assessing the residual monomer as a function of reaction time, this work also demonstrated the unusually high reactivity of 2,6-dihydroxymethyl-phenol. The rate constants for phenolic monomers toward formaldehyde substitution have been measured (Table 7.6). 

The use of HPLC for quantification of phenols is often limited to a single class of phenolics and then often only to low-molecular weight compounds that are available as standards. It is, therefore, often necessary to use colorimetric assays such as the Folin-Ciocalteau assay which rely on the reducing ability of phenols to quantify the amount of total phenolics in a sample (Waterman and Mole, 1994 Singleton et al, 1999 Schofield et al, 2001). The degree of condensation of polyphenols can be quantified by colorimetric assays such as the acid-butanol assay and the vanillin assay (Waterman and Mole, 1994 Schofield et al, 2001). 

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. 

Claycamp, H.G. (1992). Phenol sensitization of DNA to subsequent oxidative damage in 8-hydroxyguanine assays. Carcinogenesis 13, 1289-1292. 

Compounds with cis double bonds in the side chain were in general found to be more potent and efficacious than their triple-bond congeners, both in in vivo and in in vitro functional assays [98, 106, 107]. QSAR models have been generated for the compounds with unsaturated [108] and l, l -dimethyl [96] side chains to determine more precisely the pharmacophoric requirements of the receptor. It is postulated that for optimum potency, the side chain must be of a suitable length and flexibility to have the ability to loop back so that its terminus is in proximity to the phenolic ring. The widely used, potency enhancing 1 - and 2 -methyl substituents would be expected to increase the tendency of the side chain to adopt a looped back, rather than an extended conformation. 

The effects of glyphosate on phenolic compound production are two-fold 1) accumulation of phenolic compounds that are derivatives of aromatic amino acids is reduced and 2) pools of phenolic compounds derived from constituents of the shikimate pathway prior to 5-enolpyruvylshikimate-3-phosphate become larger. Assays that do not distinguish between effects on these two groups, such as that for hydroxyphenolics of Singleton and Rossi (18), can lead to equivocal and difficult to interpret results (e.g. 3-5). 

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