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The antioxidant activity of oils is an important parameter that determines oils' nutritional value and quality. To date, the methods for the determination of the antioxidant activity of oils are performed under batch conditions, therefore, they have large turnaround times and are labor-intensive. In this work, we describe the first automated method for the determination of the antioxidant activity of edible oils by resorting to the benefits of Flow Injection Analysis (FIA) and the high sensitivity of chemiluminescence (CL) detection. In the developed method, we used the chemiluminescent reaction of bis(2,4, 6-trichlorophenyl) oxalate with the reactive oxygen species produced by the catalytic decomposition of H2O2 by Mn(II) ions. The antioxidants present in the sample scavenge the reactive oxygen species and inhibit the light reaction. 1-Amino-pyrene was used as fluorophore and 1-methyl-imidazole as base catalyst in the reaction. Method validation and application to real samples showed that the analytical features of the method are very satisfactory in terms of linearity of response-lines of standard antioxidant compounds (R2 = 0.98–0.999), precision (%RSD = 0.85–1.9%) and accuracy (%recovery = 91–109%), suggesting that the developed assay could serve as an efficient tool to the routine screening of antioxidant properties in edible oils.

The lipophilicity of untreated edible oils narrows the application of most published methods for the determination of antioxidant activity to hydrophilic extracts of oils. This research addresses the issue of the estimation of the total antioxidant properties of untreated edible oils by modifying two widely applied analytical methods, the Fe-Phenanthroline and the CUPRAC assays, to be used in untreated oils. The modifications pertain to the selection of mixture of solvents (ethanol-butanol in 3:1 v/v ratio), and the optimization of the reaction conditions (reagents concentration and reaction time). The developed methods were applied to a number of hydrophilic and lipophilic standard compounds and different types of commercial edible oils, as well as their corresponding aqueous or organic extracts. This implementation elucidated the differences in the antioxidant content of edible oils. All the results were compared to those of the DPPH and Folin-Ciocalteu methods and the analytical figures of merit for the methods have been estimated. Lastly, it was concluded that the modified CUPRAC assay has higher sensitivity compared to the Fe-Phenanthroline assay.

This research dwells on two widely used spectrophotometric methods, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, which assess the free radical scavenging activity (RSA) of natural samples and standard compounds. In particular, these assays were modified in order to simplify the evaluation of RSA of untreated edible oils, as well as to assess the antioxidant profile of oils’ hydrophilic and lipophilic extracts with the same analytical procedure. A thorough study highlighted the effect of solvents on the DPPH and ABTS methods and resulted in selecting 2-propanol and an ethanol/1-butanol solvent mixture as the reaction solvent for the DPPH method and the ABTS method, respectively. The developed methods were used to evaluate the RSA of 12 antioxidant compounds and 8 edible oils. Then, the contribution of lipophilic and hydrophilic extracts to the total RSA of oils was estimated. The obtained results demonstrate the applicability of the method to routine edible oil analysis.

The ability of chiral β-amino alcohols to catalyze the direct asymmetric aldol reaction was evaluated for the first time in aqueous micellar media. A family of cheap and easily accessible β-amino alcohols, obtained in one step from naturally occurring amino acids, was shown to successfully catalyze the asymmetric aldol reaction between a series of ketones and aromatic aldehydes. These aldol reactions furnished the corresponding β-hydroxy ketones with up to 93% isolated yield and 89% ee. (S)-2-phenylglycinol and Triton X-100 proved to be the best organocatalyst and surfactant, respectively. Chirality 25:119–125, 2013. © 2012 Wiley Periodicals, Inc.

Six well established spectrophotometric assays (Folin-Ciocalteu, DPPH, ABTS•+, FRAP, CUPRAC, and the o-diphenols method) have been complementary implemented in order to estimate the total phenolic and o-diphenolic content as well as the free radical scavenging and reducing antioxidant capacities of 40 white and 10 red wines of different varieties and geographic origin. In white wines, the results were weakly correlated; whereas, the results in red wines were strongly correlated, therefore, postulating their separate use in order to estimate efficiently the correlation between results of these methods. The results were subjected to the unsupervised PCA pattern recognition method to investigate the possible classification of white wines. PC analysis framed the wine samples in clear clusters, when the extracted PCA model was based on the results of all six spectrophotometric assays. The usefulness of implementing assays based on different antioxidant mechanisms is discussed. To our knowledge, this is the fir...

The present review describes the application of luminescent methods in the analysis of edible oils without any pretreatment such as extraction prior to analysis. Emphasis has been given to applications of chemiluminescence and fluorescence assays for determining quality parameters of edible oils, such as oxidative stability, antioxidant activity, and lipid hydroperoxides content, as well as classification or adulteration of vegetable oils.

A sensitive and simple method is described for the evaluation of total antioxidant activity of olive and seed oils and their corresponding aqueous and organic extracts based on the chemiluminescent reaction of lucigenin with hydrogen peroxide. The method was fully validated for precision, trueness, robustness, additivity, and uncertainty. Validation results demonstrated that the method is able to measure the antioxidant activity of untreated edible oils as well as their hydrophilic and lipophilic extracts and posses all necessary quality factors required for routine analysis. Comparison of results with those obtained by the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and Folin–Ciocalteu methods has indicated a significant correlation between them. Furthermore, it was found that extra virgin olive oils exhibit two to three times higher total antioxidant activity than refined olive oils and seed oils, and the contribution of antioxidant activity of organic and aqueous extracts of oils to the corresponding total antioxidant activity is significantly different in olive oils than seed oils.

This paper presents an overview of flow-based methods in food and environmental analysis using chemiluminescence (CL) detection covering the period from 2005 to the present. The review discussses both automated flow methods of analysis [such as flow-injection analysis (FIA), sequential-injection analysis (SIA) and their variants] and separation techniques [liquid chromatography (LC) and capillary electrophoresis (CE) coupled to CL detection]. The most widely used CL reactions are presented together with representative applications in food and environmental analysis (determination of naturally occurring compounds, contaminants, additives as well as determination of inorganic and organic compounds).

In this study we show that nanoparticles of various ferric oxides (hematite, maghemite, amorphous Fe2O3, β-Fe2O3 and ferrihydrite) incorporated into carbon paste exhibit electro-catalytic properties towards hydrogen peroxide reduction. The modified paste electrode performances were evaluated and compared with those obtained with Prussian Blue-modified carbon paste electrode, which represents an excellent chemical mediator towards the H2O2 redox reaction (as widely described in literature). The best catalytic activity was found for carbon paste modified by amorphous ferric oxide with 2–4 nm particle size, which was further tested for possible application as hydrogen peroxide sensor. At pH 7, the limit of detection was 2×10−5 M H2O2 (S/N=3), the calibration curves were linear upto 8.5 mM H2O2 (R2=0.998), the measurement reproducibility (RSD=97%, n=4), the interelectrode reproducibility (RSD=16%, nelectrodes=5) and

A sensitive and simple method for measuring antioxidant activity was developed, based on antioxidant-dependant quenching of the chemiluminescence (CL) generated from 9-benzylacridine and potassium superoxide. This method was used to evaluate the antioxidant activity of fruit and vegetable aqueous extracts as well as of some pure phenolic compounds contained in fruits and vegetables. Coumaric, chlorogenic, caffeic, vanillic and ascorbic acids as well as (±)catechin, and 2-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox) were employed as antioxidants. It was found that the antioxidant activity of all fruit extracts is almost one order of magnitude higher than that of vegetables. Among the fruits, grapefruits show the highest antioxidant activity and pears the lowest. From the pure phenolic antioxidants, caffeic acid has the highest antioxidant activity (AA). The calculated antioxidant activities of fruit and vegetable extracts produced by the CL method are compared with other methods such as the ORAC, TEAC or DPPH method.

A sensitive and simple procedure is described for measuring the antioxidant activity (AA) of olive oil and seed oil aqueous extracts using the chemiluminescence of N , N ′-dimethyl-9,9′-biacridinium dinitrate (lucigenin). It was found that olive oil aqueous extracts showed 2–10 times higher AA than seed oils. This impressive difference is attributed to the higher content of phenolic compounds present in olive oils. Spectrophotometric and fluorimetric measurements affirmed this hypothesis. As shown in this paper, the reported method could also be used for the quantitation of total phenols in aqueous oil extracts. It was found that commercial and non-commercial Greek olive oil aqueous extracts contain 55.3–125.9 mg caffeic acid equivalents per kilogram, while seed oils, only 0.6–3.2 mg kg −1 .

A weak chemiluminescence (CL) emission was observed in commercial Greek extra virgin olive oils (Knossos, Spitiko, Ananias, Altis, Minerva, Xenia) and in refined seed oils such as sunflower oils (Marata, Sanola, Sun, Mana, Sol, Minerva) as well as in corn oils (Flora, Minerva, Marata Sun and Sol) with potassium superoxide in the aprotic solvent dimethoxyethylene. On measuring the CL of mixtures of extra virgin olive oils with the cheaper refined seed oils, calibrations were produced which can be used for the determination of the adulteration of olive oils with seed oils down to 3%. Furthermore, depending on the kind of oils, “low” authenticity-CL-factors for olive oils (0.8–2.15 μmol l−1 gallic acid) and “high” for seed oils (4.5–11.2 μmol l−1 gallic acid) were calculated.

A sensitive and simple method for measuring antioxidant activity was developed, based on antioxidant-dependant quenching of the chemiluminescence (CL) generated from photolyzed acridine and methanolic potassium hydroxide. This method was used to evaluate the antioxidant activity of food additives by measuring the inhibition of CL at a gradient of antioxidant concentrations. Adipic, tartaric, citric, ascorbic, malic, fumaric and 6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid (Trolox) were employed as antioxidants. The method is more suitable for lipophilic compounds.

The light reaction of protected hemiaminal 3 (N-methoxymethyl-′-methyl-9,9′-biacridylidene) with singlet oxygen and alkaline hydrogen peroxide in homogeneous and micellar media is reported. The chemiluminescence and fluorescence quantum yields and light intensities in those media are also reported. Hemiaminal 3 is suitable for competition reactions in the presence of organic reductants for analytical applications.

The chemiluminescent reaction of five N,N ′-dilakyl-9,9′-biacridinium nitrates, C 1 , C 4 , C 6 , C 10 and C 12 , with hydrogen peroxide in alkaline aqueous and micellar solutions is reported. The chemiluminescence and chemiexcitation yields in these media are reported together with the chemical yields and the fluorescence quantum yields of the long chain N -alkylacridones, the primary emitters, in cationic, anionic and non-ionic micellar media. Based on the chemiluminescence profiles the reaction rate constants and chemiluminescence intensities are reported.

The racemic and enantioselective synthesis of a novel glyceric acid derivative, namely, 2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid as well as the antioxidant activities is described. The virtually pure enantiomers, (+)-(2R,3S)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid and (-)-(2S,3R)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid were synthesized for the first time via Sharpless asymmetric dihydroxylation of trans-caffeic acid derivatives using the enantiocomplementary catalysts, (DHQD)(2)-PHAL and (DHQ)(2)-PHAL. The determination of enantiomeric purity of the novel chiral glyceric acid derivatives was performed by high-performance liquid chromatographic techniques on the stage of their alkylated precursors. The novel glyceric acid derivatives show strong antioxidant activity against hypochlorite and N,N-diphenyl-N-picryl-hydrazyl free radical. Their antioxidant activity is about 40-fold higher than that of the corresponding natural polyether and three-fold higher of trans-caffeic acid itself.

A sensitive and simple procedure is described for evaluating the antioxidant activity of 21 known hydrophilic and hydrophobic compounds by using the chemiluminogenic reaction of lucigenin with hydrogen peroxide. The method was validated for linearity, limit of detection, precision, additivity and ruggedness and compared to the DPPH method. Furthermore, the IC(50) values of all compounds were calculated and compared by both methods and results are discussed on the basis of structure-antioxidant activity relationship. Among hydrophilic antioxidants, phenolic compounds with adjacent hydroxyl groups (gallic acid, caffeic acid, pyrocatechol, (+/-)-catechin, oleuropein) were found to be efficient antioxidants in chemiluminescence method with IC(50) values at the sub-micromolar range, while phenolic compounds without adjacent hydroxyl groups (p-coumaric acid, BHT, BHA, resorcinol) exhibited weak activity with IC(50) values>10microM. Alpha-tocopherol was the most efficient hydrophobic antioxidant (IC(50)=6.7microM) while oleic and linoleic acids were found to be very poor antioxidants (IC(50)>300microM). Finally the method was applied to the estimation of antioxidant activity of complex samples such as olive oils. To the best of our knowledge, this is the first time that total antioxidant activity can be determined directly in olive oil and not in aqueous extracts.

The effect of various concentrations of essential alpha-amino acids on the luminol-sodium hypochlorite chemiluminescence (CL) has been studied. It was found that all tested compounds have an inhibiting effect. Amino acids with phenolic groups present higher inhibition than basic, acidic or neutral amino acids. The calculated antioxidant activities by the CL method are compared with those of the N,N-diphenyl-picryl hydrazyl (DPPH) method.

The use of liposomes has been crucial for investigations in biomimetic chemical biology as a membrane model and in medicinal chemistry for drug delivery. Liposomes are made of phospholipids whose biophysical characteristics strongly depend on the type of fatty acid moiety, where natural unsaturated lipids always have the double bond geometry in the cis configuration. The influence of lipid double bond configuration had not been considered so far with respect to the competence of liposomes in delivery. We were interested in evaluating possible changes in the molecular properties induced by the conversion of the double bond from cis to trans geometry. Here we report on the effects of the addition of trans-phospholipids supplied in different amounts to other liposome constituents (cholesterol, neutral phospholipids and cationic surfactants), on the size, fl-potential and stability of liposomal formulations and on their ability to encapsulate two dyes such as rhodamine B and fluorescein. From a biotechnological point of view, trans-containing liposomes proved to have different characteristics from those containing the cis analogues, and to influence the incorporation and release of the dyes. These results open new perspectives in the use of the unnatural lipid geometry, for the purpose of changing liposome behavior and/or of obtaining molecular interferences, also in view of synergic effects of cell toxicity, especially in antitumoral strategies.