ABSTRACT
A novel fluorimetric method is described for the evaluation of the antioxidant activity of hydrophilic and lipophilic compounds and complex natural products such as edible oils. The method is based on the measurement of fluorescence emission intensity of N-methylacridone produced during the reaction of lucigenin with hydrogen peroxide. The presence of antioxidants in the sample inhibits the concentration of N-methylacridone and reduces the fluorescence intensity. The method was fully validated and applied to a variety of hydrophilic and lipophilic compounds as well as to various types of edible oils and their corresponding hydrophilic and lipophilic extracts. Results were compared to those derived from a lucigenin based chemiluminescent method and the Folin-Ciocalteau method for total phenols. The differences in total antioxidant activity of edible oils of various origins and the effect of heating on total antioxidant activity was further studied and discussed.
Subject(s)
Antioxidants/pharmacology , Fluorometry/methods , Plant Oils/pharmacology , Antioxidants/chemistry , Drug Evaluation, Preclinical , Plant Oils/chemistryABSTRACT
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.
