Determination of Antioxidant Biomarkers in Biological Fluids

Abstract

The presence of various bioactive markers in the human body reflects its health condition, physical endurance, and also the intake of some valuable compounds from food. Analytical methods for their determination are becoming a useful tool for gaining information on the levels of these physiologically essential substances. Antioxidants that can prevent or slow the harmful action of free radicals belong to one of the most significant biomarkers. Reactive oxygen species/reactive nitrogen species produced under oxidative stress act together and cause damage to all cellular biomolecules. Therefore excessive levels of such reactive species pose a threat to human organisms contributing to inflammatory responses. For measurements of oxidative stress or damage indicators, both the reactive species are analyzed, and also different markers considered useful indexes of the level of the phenomenon are determined. Biological samples usually include whole blood derivatives (serum and plasma), urine, and saliva. The fluorescence methods are most commonly applied for the determination of oxygen radicals. At the same time, markers of cellular oxidative damage are most often tested in body fluids and tissue homogenates using enzyme-linked immunoassay kits, high-pressure liquid chromatography, or even gas chromatography, both combined with mass spectrometry. For the assay of protein carbonyls in biological matrices, the derivatization of the carbonyl group, usually with 2,4-dinitrophenylhydrazine, is performed and followed by the detection of various types, for example, using anti-DNP antibodies in immunoblotting.