Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı 2

The Effects of Interactions of Polyphenols with Thiols and Proteins on Certain Methods of Antioxidant Activity Determinations

Laboratory studies which aim to determine total antioxidant capacity (TAC) or activity give an idea on the bioavailability of polyphenols, due to complex composition of food, structure, other nutrients consumed together, metabolic activities in the body the reality of ingested polyphenols actually interact with other compounds should be noted. Especially the interaction between proteins and polyphenols must be considered in this respect. Polyphenols found in food not only interact with salivary or alvine proteins and digestive enzymes but also they are transported via binding to plasma proteins in the body. Thiol compounds, contained in the protein structure and known with their antioxidant properties, need to be carefully evaluated in terms of their interaction with polyphenols.

In this study the protein-polyphenol interactions were investigated by common methods used for determination of antioxidant activity/capacity namely modified CUPRAC method, ABTS/Persulfate radical scavencing assay, FRAP assay and DPPH. In addition to antioxidant activity/capacity methods, to determine thiol compounds Ellman and a method based on indophenol dye formation on indophenol dye formation on nano-sized TiO₂ method, which mentioned in our previous study for determination of catechin, were used. These methods were applied to selected various of polyphenol compounds and reaction system which consists of only protein/thiol or their mixture were examined. Observed error% values were ranged between -0,40 and -29,27 ; -21,06 and 0,20 for CUPRAC, ABTS methods respectively. For DPPH and thiol determination method based on formation of indophenol dye on solid phase the observed error % values were above 20%. Additionally in FRAP method great pozitive errors were determined for thiol containing mixtures. The results showed that the possibility of formation of intermediate products and covalent binding between thiols and protein or polyphenols were very low. The differences among the results can be expressed as variations in experimental conditions and suitability of the used methods for related samples.
  

DURUSOY Nazan

Danışman : Doç. Dr. Mustafa ÖZYÜREK

Anabilim Dalı : Kimya

Programı : Analitik Kimya

Mezuniyet Yılı : 2014

Tez Savunma Jürisi : Doç. Dr. Mustafa ÖZYÜREK

Doç. Dr. Kubilay GÜÇLÜ

Prof. Dr. İkbal KOYUNCU

Doç. Dr. Mehmet ALTUN

Doç. Dr. Mehmet A. Faruk ÖKSÜZÖMER