Oxidative stress is a state of impaired balance between the formation of free radicals and antioxidant capacity of the body. It causes many defects of the body, e.g. lipid peroxidation, DNA and protein damage. In order to prevent the effects of oxidative stress, the organism has developed defence mechanisms. These mechanisms capture and inhibit the formation of free radicals and also chelate ion metals that catalyse free radical reactions. Trace elements are components of antioxidant enzymes involved in antioxidant mechanisms. Selenium, as a selenocysteine, is a component of the active site of glutathione peroxidase (GPx). The main function of GPx is neutralization of hydrogen peroxide (H2O2) and organic peroxide (LOOH). Furthermore, selenium is a structural part of a large group of selenoproteins that are necessary for proper functioning of the body. Manganese, copper and zinc are a part of the group of superoxide dismutase enzymes (MnSOD, Cu/ZnSOD), which catalyse the superoxide anion dismutation into hydrogen peroxide and oxygen. Formed hydrogen peroxide is decomposed into water and oxygen by catalase or glutathione peroxidase. An integral component of catalase (CAT) is iron ions. The concentration of these trace elements has a significant influence on the activity of antioxidant enzymes, and thus on defence against oxidative stress. Even a small change in the level of trace elements in the tissue causes a disturbance in their metabolism, leading to the occurrence of many diseases.

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Ethanol intoxication leads to oxidative stress, which may be additionally enhanced by aging. The aim of this study was to investigate the influence of green tea as a source of water-soluble antioxidants on the ability to prevent oxidative stress in aged rats sub-chronically intoxicated with ethanol. Two-, 12-, and 24-mo-old male Wistar rats were divided into 4 experimental groups: (1) control, (2) green tea, (3) ethanol, and (4) ethanol and green tea. Ethanol intoxication produced age-dependent decrease in the activity of serum superoxide dismutase, glutathione peroxidase, and reductase and in levels of glutathione (GSH), vitamins C, E, and A, and beta-carotene. Changes in the serum antioxidative ability were accompanied by enhanced oxidative modification of lipid (increase in lipid hydroperoxides, malondiadehyde, and 4-hydroxynonenal levels) and protein (rise in carbonyl group levels). Green tea partially protected against changes in antioxidant enzymatic as well as nonenzymatic parameters produced by ethanol and enhanced by aging. Administration of green tea significantly protects cellular components such as lipids and proteins against oxidative modification. Results indicate that green tea effectively protects blood serum against oxidative stress produced by ethanol as well as aging.

Fatty acids participate in different metabolic mechanisms, but their key role is connected with their participation in membrane phospholipid organizations. This review introduces the current knowledge of fatty acid analysis with an emphasis on the analysis of these compounds in biological samples. Therefore this manuscript is focused on various aspects of biological sample preparation methods, such as lipid extraction, lipid and phospholipid fractionation (TLC and SPE), derivatization, and on the methodologies of fatty acid analysis by gas chromatography (GC) and high-performance liquid chromatography (HPLC). The wide spectrum of columns and detectors used in these techniques for selective separation and determination of bioactive fatty acids are discussed. The abilities of using a sensitive tandem LC/MS and GC/MS assay are also shown.

Determination of cathepsin D (Cat D) concentration in serum and urine may be useful in the diagnosis of bladder cancer. The present study included 54 healthy patients and 68 patients with bladder cancer, confirmed by transurethral resection or cystectomy. Cat D concentration was determined using a surface plasmon resonance imaging biosensor. Cat D concentration in the serum of bladder cancer patients was within the range of 1.3–5.59 ng/ml, while for healthy donors it was within the range of 0.28–0.52 ng/ml. In urine, the Cat D concentration of bladder cancer patients was within the range of 1.35–7.14 ng/ml, while for healthy donors it was within the range of 0.32–0.68 ng/ml. Cat D concentration may represent an efficient tumor marker, as its concentration in the serum and urine of transitional cell carcinoma patients is extremely high when compared with healthy subjects.