Pro-oxidant and antioxidant activity of quinones and nitroazoles in flaxseed oil

Abstract

Quinones are one of the most commonly used drugs for cancer treatment. Combinations of quinoid compounds and other oxidation inducers with flaxseed oil (FO), which is rich in omega-3 alpha-linolenic acid, show promise for improving the efficacy of antitumor drugs. Effects of benzo-, naphtho-, and anthraquinones, as well as metronidazole and a number of nitro-1,2,4-triazoles on the oxidative stability of FO, were studied. To this end, kinetic curves were obtained showing the accumulation of hydroperoxides in FO during storage at 37°C with free access to atmospheric oxygen. The calculated oxidation induction period demonstrates that the majority of the tested quinones intensify the oxidation of FO. Pro-oxidant activity is maximum for 1,4-benzoquinone and significantly decreases (p < 0.05) when various substituents are introduced into its ring. A noticeable increase in the concentration of hydroperoxides and the rate of oxidation at the initial stage of the oxidation process is characteristic for 1,4-benzoquinone and its derivatives. Additives of 1,4-naphthoquinone and 2-hydroxy-1,4-naphthoquinone (lawsone) do not affect the oxidative stability of FO, while 5-hydroxy-1,4-naphthoquinone (juglone) and 4,6-di-tert-butyl-1,2-benzoquinone effectively inhibit the oxidation of FO. The oxidation of FO lipids is accelerated by all investigated nitroazoles; however, 1-methyl-3,5-dinitro-1,2,4-triazole has the highest pro-oxidant activity.

Practical Applications: The results of this study may be useful in the development of new methods of antitumor therapy using omega-3 polyunsaturated substrates in combination with quinoid and nitrotriazole cytostatics. The data obtained can also be used in the development of oxidation-stable foods based on flaxseed oil, as well as in the production of resins, drying oils, varnishes, paints, and other materials.