Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

The Correlatıon Between Reactıve Oxygen Specıes Consumptıon Of

Antıoxıdants AndTheır Cuprac Antıoxıdant Capacıty

Oxygen is essential for life, but it may also have harmful effects on the organism. Oxygen forms various reactive oxygen species (ROS), i.e.,superoxide, singlet oxygen, hydroxyl radical etc, in the respiratory chain. Reactive oxygen species are scavenged by synthetic or dietary taken antioxidants. Therefore measurement of the radical scavenging activity of these antioxidants has great importance. In this study Reactive Oxygen Species (ROS) were generated by Fe(II)-H₂O₂ and Fe(III)-H₂O₂ reaction. ROS scavenging activity of the synthetic antioxidants added in the same medium were determined with thiobarbituric acid reactive substances (TBARS), and N, N-dimethyl-p-phenylenediamine (DMPD) methods and so the "Total Oxidative Conversion (TOC)" were determined. Total antioxidant capacities (TAC) of selected antioxidants were measured with CUPRAC (cupric reducing antioxidant capacity) method and trolox equivalent antioxidant capacity (ABTS / TEAC) method. The method was applied to the synthetic antioxidants firstly and later it was applied to a real biological fluid namely serum.

The experiments made in this work showed that, there is a linear relationship between antioxidant molar concentration and absorbance changes in the CUPRAC and ABTS methods of TAC measurement, i.e. abs. (or Δabs.) increases linearly with antioxidant concentration. The highest linear correlation coefficients (r² > 0.99) comprising all tested antioxidants were obtained for the CUPRAC method. On the other hand, there is a distinct decrease of ROS (measured as TOC) with increasing amounts of antioxidants, as reflected by the decreasing absorbances of DMPD and TBARS methods in response to antioxidant addition. This decrease was almost linear or curvi-linear for DMPD, and pseudo-linear or basically non-linear for TBARS.
This work has established an inverse relationship between oxidative conversion and antioxidant capacity in the form of a curvi-linear relation between the absolute values of increments in TAC and decrements in TOC as a function of added antioxidant concentration. This simple relationship between TAC and TOC may initiate the formation of a bridge between medical bioanalytical chemistry mainly relying on TOC results and food analytical chemistry often using TAC results, because these two disciplines are known to frequently use quite different languages. Thus, the accurate and precise measurement of serum antioxidant capacity may play an important role in monitoring the diagnosis and treatment process of diseases.