Examination of antioxidant capacity parameters

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

Determination of oxygen radicals

 * pulsed radiolysis - radicals are generated by ionizing radiation
 * electron spin resonance spectrometry (ESR) - identification according to spin changes
 * chemiluminescence method

Determination of nitrogen radicals and its adducts

 * nitric oxide - very difficult to determine
 * methods such as 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 (catalyses reactions where free radicals are formed)

Indirect measurements

 * most often determination of lipoperoxidation products, adducts with DNA

Damage to NK

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

Damage to proteins and AMK

 * many damage mechanisms, little used
 * a 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 color complex, non-specific, also reacts eg bilirubin, DNA
 * also other aldehydes (eg 4-hydroxynonenal)
 * conjugated dienes - characteristic UV absorption (234 nm)
 * measurement of hydrocarbons in exhaled air
 * isoprostanes - by peroxidation product of arachidonic acid

Oxidized LDL

 * contribution to atherosclerosis
 * 2 methods


 * 1) delayed phase change during 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 - ability of plasma after the addition of a generator - conversion to the Trolox capacity - 1 molecule of trolox has 2.0 units when using TRAP - disadvantage - end-point oxygen electrode
 * more used ABTS - inhibition of 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 liquid chromatography (HPLC)

Related Articles

 * Basic reactive forms of oxygen and nitrogen

Source

 * ws: Vyšetření parametrů antioxidační kapacity