Uric acid is the end product of purine metabolism in men. It was pointed out, that this compounds act as an antioxidant and is capable to react with biologically-relevant oxidants to form allantoin. Therefore, measurement of allantoin in men was proposed as a marker of oxidative stress. We estimated allantoin in human plasma using a method based on selective isolation of allantoin from deproteinised plasma samples on AG 1-X8 resin and its derivatization to glyoxylate-2,4-dinitrophenyl hydrazone. The method is free from urate and glyoxylate interfe- rences. Separation of glyoxylate from other hydrazones was achieved on reversed phase HPLC with gradient elution and UV-VIS detection at 365 nm. The analytical performance of this method is satisfactory with intra-assay CV 8.7%, inter-assay 9.7% and 90.8% recovery. The preliminary reference range of allantoin in a group of blood donors is 2.1 ± 1.3 mmol/l.

        Key words: allantoin, uric acid, oxidative stress, reactive oxygen species, HPLC.