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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.

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.