Analytica Chimica Acta 494 (2003) 41–47 Comparative studies on the antioxidant activity of aqueous extracts of olive oils and seed oils using chemiluminescence K. Papadopoulos a,∗ , T. Triantis b , E. Yannakopoulou a , A. Nikokavoura a , D. Dimotikali b a Institute of Physical Chemistry, NCSR “Demokritos”, 15310 Ag. Paraskevi, Athens, Greece b Chemical Engineering Department, NTU Athens, Iroon Politechniou 9, 15780 Athens, Greece Received 18 March 2003; received in revised form 15 July 2003; accepted 1 August 2003 Abstract 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 . © 2003 Elsevier B.V. All rights reserved. Keywords: Chemiluminescence; Olive oils; Antioxidant activity; Phenols 1. Introduction Olive oils have been identified as one, if not the ma- jor healthful component of the Mediterranean diet, a diet that is synonymous with lowered rates of heart dis- ease, cancers and extended life expectancy. All these properties were attributed to the very high content of mono-unsaturated fatty acids and phenolic com- pounds from simple to very complex structures [1–4]. The knowledge that many of these compounds react with various free radicals or reactive oxygen species [5,6] influencing the oxidative stability of oils [7–12] and the knowledge that many chemiluminescent (CL) ∗ Corresponding author. Tel.: +30-210-650-3647; fax: +30-210-651-1766. E-mail address: kyriakos@chem.demokritos.gr (K. Papadopoulos). reactions proceed on reaction with reactive oxygen species or free radicals [13,14], all these encouraged us to expect that the use of edible oil extracts in such reactions would reduce the light signals giving us the possibility to estimate their AA. As shown later, these CL experiments could also lead to the determination of the total phenols in oil extracts. To our knowledge, a number of assays have been published for the evaluation of the total AA of olive oil extracts, using colorimetric, spectrophotometric, elec- trochemical or chromatographic techniques [15–24], but little attention has been paid to CL methods. There- fore, in this paper we report a novel and simple CL method for the evaluation of the AA of commercial olive oils and seed oils aqueous extracts. As the CL detection system we used lucigenin (N,N ′ -dimethyl- 9,9 ′ -biacridinium dinitrate) and alkaline hydrogen 0003-2670/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0003-2670(03)01013-4