1 3 Eur Food Res Technol DOI 10.1007/s00217-015-2529-4 ORIGINAL PAPER Assessment of antioxidant properties of alpha‑keto acids in vitro and in vivo Maria M. Bayliak 1 · Maria P. Lylyk 1 · Oksana M. Vytvytska 1 · Volodymyr I. Lushchak 1 Received: 6 June 2015 / Revised: 3 August 2015 / Accepted: 5 August 2015 © Springer-Verlag Berlin Heidelberg 2015 Keywords Alpha-ketoglutarate · Oxaloacetate · Pyruvate · H 2 O 2 scavenging · Saccharomyces cerevisiae · Drosophila melanogaster Abbreviations ABTS 2′-Azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt AKG Alpha-ketoglutarate KA/KAs Keto acid/keto acids OA Oxaloacetate ROS Reactive oxygen species TAA Total antioxidant activity TCA Trichloroacetic acid Introduction Reactive oxygen species (ROS), such as superoxide anion radical (O 2 ·− ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radi- cal (HO · ), are normal by-products of aerobic cellular metab- olism, and their production is enhanced by environmental stressful factors. Playing important physiological functions in cellular signaling at low levels, ROS become dangerous for cells at high levels and may cause wide-ranging damage to biomolecules that can eventually lead to cell death. To pro- tect themselves against these damages, cells have effective defense mechanisms, including antioxidant enzymes and non-enzymatic free radical scavengers, to maintain ROS at certain steady-state level [1]. When ROS production exceeds the antioxidant capacity, cells undergo an oxidative stress characterized by increased oxidative processes and accumula- tion of oxidatively damaged proteins, lipids and DNA. Oxida- tive stress is a common hallmark accompanying various stress challenges, as well as aging and numerous diseases, including cancer, cardiovascular and neurodegenerative disorders [2–4]. Abstract The antioxidant properties of three alpha-keto acids, pyruvate, oxaloacetate and alpha-ketoglutarate were tested in vitro and in vivo. In vitro, the keto acids dem- onstrated a good H 2 O 2 -scavenging activity, but were less effective as scavengers of free radicals or reductants of oxi- dized compounds. Alpha-ketoglutarate was a more effec- tive H 2 O 2 scavenger as well as HO · in Fe 3+ –ascorbate– EDTA–H 2 O 2 system than other keto acids. All keto acids did not demonstrate iron-chelating activity. It was sup- posed that ability of keto acids to inhibit HO · production in the Fenton reaction could be mainly conditioned by their H 2 O 2 -scavenging activity. In vivo experiments, the addition of alpha-keto acids to the incubation medium significantly increased the resistance of exponentially growing yeast Saccharomyces cerevisiae cells to H 2 O 2 , transition metal ions (Fe 2+ ), but not to menadione, a superoxide anion-gen- erating compound. Similar results were obtained on fruit fly Drosophila melanogaster. In particular, co-treatment with alpha-ketoglutarate enhanced resistance of adult flies to H 2 O 2 and did not prevent menadione-induced death of flies. Collectively, the results obtained indicate that exoge- nous alpha-keto acids as antioxidants are able efficiently to protect living organisms against stressors in which effects are mediated by H 2 O 2 . Therefore, they can be considered as available natural supplements to alleviate the harmful effects of reactive oxygen species. * Maria M. Bayliak bayliak@ukr.net 1 Department of Biochemistry and Biotechnology, Vasyl Stefanyk Precarpathian National University, 57 Shevchenko Str., Ivano-Frankivsk 76018, Ukraine