Antioxidants analytical methods

PRIOR R L and CAO G (1999) "In vivo total antioxidant capacity Comparison of different analytical methods, Free Rad Biol Med, 27, 1173-81. 

More recently, the same author [41] has described polymer analysis (polymer microstructure, copolymer composition, molecular weight distribution, functional groups, fractionation) together with polymer/additive analysis (separation of polymer and additives, identification of additives, volatiles and catalyst residues) the monograph provides a single source of information on polymer/additive analysis techniques up to 1980. Crompton described practical analytical methods for the determination of classes of additives (by functionality antioxidants, stabilisers, antiozonants, plasticisers, pigments, flame retardants, accelerators, etc.). Mitchell... 

C12 to C20, primarily Ci6 to ( is), used as surface lubricants in the manufacture of food-contact articles. The method, which uses ethyl palmitate (Eastman Chemicals No. 1575 Red Label) as an internal standard, has been validated at 200 ppm total FAME [185]. Other FAME standards (methyl palmitate, methyl stearate, methyl oleate, methyl linoleate and methyl linolenate) are available (Applied Science Laboratories) [116], Worked out examples of additive determinations are given in the Food Additives Analytical Manual [116], which also describes a great many of indirect food additives, such as BHA, BHT, TBHQ, l-chloro-2-propanol, DLTDP, fatty acid methyl esters, w-heptyl-p-hydroxybenzoate, propyl-gallate, sodium benzoate, sodium stearoyl-2-lactylate, sorbitol and phenolic antioxidants. EPA methods 606 and 8060 describe the CGC separation of phthalate esters (direct injection) (cf. Figure 4.2). 

FD-MS is also an effective analytical method for direct analysis of many rubber and plastic additives. Lattimer and Welch [113,114] showed that FD-MS gives excellent molecular ion spectra for a variety of polymer additives, including rubber accelerators (dithiocar-bamates, guanidines, benzothiazyl, and thiuram derivatives), antioxidants (hindered phenols, aromatic amines), p-phcnylenediamine-based antiozonants, processing oils and phthalate plasticisers. Alkylphenol ethoxylate surfactants have been characterised by FD-MS [115]. Jack-son et al. [116] analysed some plastic additives (hindered phenol AOs and benzotriazole UVA) by FD-MS. Reaction products of a p-phenylenediaminc antiozonant and d.v-9-lricoscnc (a model olefin) were assessed by FD-MS [117],... 

Tea (Camellia sinensis) is one of the most frequently consumed beverages in the world and, consequently, an important agricultural product [168], It has been proved many times that tea may reduce cholesterol level, hypertension, and shows antioxidant and anti-microbial effects [169], Because of its importance, a considerable number of analytical methods have been developed for the separation and quantitative determination of the constituents of tea [170,171]. Thus, the application of high-speed counter-current chromatography [172,173], and HPLC-APCI-MS [174] have been reported. 

Figure 6.5 shows the structures of tra 5-cinnamic acid and four cinnamic acid derivatives (phenolic compounds) reported to be present in potatoes. Because potatoes are one of our major food plants, we validated with the aid of HPLC and LC/MS the content and distribution of antioxidative phenolic compounds in parts of the potato plant, in potato tubers, in the peel and flesh of tubers, in potatoes sold commercially in Korea and the United States, and in home-processed potatoes. The following discussion, based on our own studies, is followed by a brief overview of analytical methods for potato phenolic compounds by other investigators. 

As classical analytical methods only give delayed results, no evolution of the global antioxidant capacity of these media with time can be examined. For the first time, owing to fast response of cyclic voltammetry, the presented direct electrochemical measurements give results in real time, thus allowing the monitoring of reaction kinetics. 

C9. Cao, G., and Prior, R. L., Comparison of different analytical methods for assessing total antioxidant capacity of human serum. Clin. Chem. 44,1309-1315 (1998). 

Litwinienko et al. (1997) reported that non-isothermal (conventional) DSC and P-DSC analyses can evaluate antioxidant activity in linolenic (Ci8 3) acid doped with phenolic antioxidants. Activation energies were inferred by applying the Ozawa-Flynn-Wall analytical method. Results showed that increasing BHT loading from 0.3 to 4.0mM increased the activation energy of oxidation from 73.0 to 97.8kJ/mol. 

The increasing interest in a-tocopherol as the principal lipid-soluble antioxidant in mammalian cells creates a need for rapid, reproducible and accurate methods for measurement of the vitamin in body fluids, cultured cells, whole tissues and, in some instances, in food products. Early methods identified a number of difficulties that arise in achieving this analytical objective and an understanding of the possible problems that may arise is fundamental to the successful application of the chosen analytical methods. The early methods were summarized in three categories (Bunnell, 1971) which cover the three stages of analysis that may still be found to be necessary with the availability of modem analytical techniques. These stages are ... 

Stalikas, C.D. 2008. Phenolic acids and flavonoids occurrence and analytical methods. In Free Radicals and Antioxidant Protocols, Methods in Molecular Biology, 2nd edn. (Uppu, R.M. Murthy, S.N. Pryor, W.A. Parinandi, N.L., Eds.). Humana Press, New York, pp. 65-90. 

Flavonols and flavones are present in many food products and medicinal plants and show relevant antioxidant activity in vitro. In this chapter, classical analytical methods sueh as thin layer ehromatography and two-dimensional paper chromatography together with modem methodologies such as HPLC-MS-MS are reported. Preparative ehromatography methods are also reviewed as well as spectroseopie methods used for flavonoid characterization and identification, including UV spectrophotometry and MS spectrometry. Chemical and enzymatic methods used in flavonoid identification are also reviewed. 

Extensive reviews of analytical methods for anthocyanins (Francis, 1982 Jackman et al., 1987b Strack and Wray, 1994) and other flavonoids (Williams and Harbome, 1994) as well as phenolic acids (Herrmann, 1989) have been published. In these reviews, extraction procedures, methods for fractionation of groups of polyphenols and the identification and quantification of individual components are presented. Here, a brief presentation of more recently published methods for grape and berry polyphenolic analyses is given with respect to their relationship to antioxidant activity and health benefits. 

Prior RL, Cao G. In vivo total antioxidant capacity comparison of different analytical methods. Free Radic Biol Med 1999 27 1173-81. 

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