Investigation of antioxidant capacity parameters

Direct measurement is difficult due to the short half-life of free radicals (VR). Substances formed by their action are determined.

Determination of oxygen radicals

 * pulse radiolysis – radicals are generated by ionizing radiation
 * electron spin resonance spectrometry (ESR) – identification based on spin changes
 * chemiluminescence method

Determination of nitrogen radicals and their adducts

 * nitric oxide – it is very difficult to determine
 * methods as in oxygen
 * most often indirect methods - nitrites, nitrates or substances modified by nitration - nitrosohemoglobin

Determination of radical generating substances

 * xanthine oxidase – produces superoxide
 * determination of transition metals – Fe, Cu (they catalyze reactions where free radicals are formed)

Indirect measurements

 * most often determination of lipoperoxidation products, adducts with DNA

NK damage

 * the most significant (irreversible) damage – by the hydroxyl radical
 * main product – thymine glycol and 8-hydroxyguanine
 * repair enzymes remove them from the cells - we can determine them in the urine

Damage to proteins and AMK

 * many damage mechanisms, little used
 * sensitive method is for measuring carbonyl residues from lysine.

Lipoperoxidation

 * in direct connection with the formation of free radicals
 * most common – determination of malondialdehyde (MDA) – reaction with thiobarbiturate forms a colored complex, non-specific, also reacts with e.g. bilirubin, DNA
 * also other aldehydes (e.g. 4-hydroxynonenal)
 * conjugated dienes – characteristic UV absorption (234 nm)
 * measurement of hydrocarbons in exhaled air
 * isoprostanes - by peroxidation of products arachidonic acids

Oxidized LDL

 * share of atherosclerosis
 * 2 methods


 * 1) change of the delay phase in stimulated peroxidation - examines the ability of LDL to cope with oxidative stress
 * 2) determination of oxLDL – extraction, oxFFA is determined at 234 nm

Total antioxidant capacity

 * artificial formation of free radicals in biological material - we measure the ability to slow down or stop this reaction
 * TRAP determination – plasma capacity after adding the generator – conversion to Trolox capacity – 1 trolox molecule has 2.0 units when using TRAP – disadvantage – end-point oxygen electrode
 * more commonly used ABTS – inhibition of the ABTS radical cation

Antioxidant enzymes

 * determination of SOD rather indirectly, determination of catalase – rarely

Antioxidant substrates

 * vitamins A, E, C
 * determination of thiols is irrelevant (they are on albumin, they have a long half-life)
 * also others - ubiquinone Q, lipoate, flavonoids..., using high-performance (high-pressure) liquid chromatography (HPLC)

Related Articles

 * Basic reactive forms of oxygen and nitrogen