Univ. Doz. Dr. John Ionescu Gründer und wissenschaftlicher Leiter der Spezialklinik Neukirchen Dozent an der Donau Universität Krems, Österreich Mitglied der Europäischen Akademie für Allergologie und klinische Immunologie Mitglied der Europäischen Akademie für Umweltmedizin
1 Spezialklinik Neukirchen, Neukirchen Germany
2 Dept. of Medical Nutrition, Donau University Krems, Austria
3 Laboratory for ageing process research, Chair of Environmental Health, Faculty of Health Studies, University of Ljubljana, Slovenia
Vitamin C is an acidic molecule with strong reducing activity. It is an essential micronutrient in man, due to the absence of L-gulonolactone oxidase. Vitamin C has several important roles and there are many enzymes utilizing ascorbate as a co-factor. Besides, vitamin C protects human health by scavenging toxic free radicals and other reactive oxygen species (ROS) formed in cell metabolism. On the other side, it is well established by in vitro experiments that vitamin C is reactive with free iron and other transition metals and produces free radicals, while causing oxidative damage to biomolecules. The interaction of ascorbic acid with transition metal ions could promote their reduction, accompanied by increased H2O2 production and consequently OH• formation. There is still debate on whether supplements of vitamin C could act as antioxidant or pro-oxidant in vivo. Recent research suggests that 3 factors are responsible for the pro- or antioxidant behaviour of vitamin C in biological systems, e.g. cellular environment:1.) the redox potential of the cellular environment (oxidosis/redosis), 2.) the presence or absence of transition metals and 3.) the local concentration of ascorbate. This may also explain the observed quite specific pro-oxidant activity of high dose intravenous vitamin C against metal rich malignant tumours. In this paper anti- and pro- oxidant effects of vitamin C will be presented and their potential impact on cancer prevention and treatment will be discussed.
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