KRISTINOVÁ, V. Zhodnocení antioxidačního působení za použití různých analytických metod [online]. Brno: Vysoké učení technické v Brně. Fakulta chemická. 2008.

Posudek vedoucího

Rustad, Turid

This is a very good thesis - also compared to Norwegian standards. The student has worked independently and has a good grasp of her subject. The experimental work is of high standard and the presentation and discussion of the results are also on a very high level.

Posudek oponenta

Mozuraityte, Revilija

Thesis, written by Vera Kristinova, consist of 106 pages of discussion on evaluation of antioxidant effect using different analytical methods, 98 literature sources are cited. Thesis has a logical structure; data given in the thesis provide better understanding on influence of different phenolic compound on lipid oxidation. It also shows the advantages and disadvantages of different methods that can be used to evaluate antioxidant capacity (AOC) of phenolic compound. Small comment should be mentioned: Reference number in the text should be given in an order of appearance. Theory part includes an overwiev about lipids oxidation. In pg 18 termination phase in lipid oxidation is described. However, it is difficult to understand what the author does mean: "In the termination phase, free radicals react with each other to form stable non-radical endproducts (secondary oxidation compounds). These reactions lead to the formation of hydrocarbons, aldehydes, alcohols and volatile ketones." Does these radicals-radicals reactions leads to formation of volatiles (low molecular weight) compounds? Maybe author can comment what is "highly oxidised fat " pg 31 in the folloving sentence: "Antioxidants are more effective when added to lipids with a low degree of oxidation; they are poorly effective in retarding oxidation in highly oxidised lipids." Also why are antioxidants poorly effective in oxidised fat? Experiment part. Enough information is given about the methods that were used in the studies. So, other scientists can be able to repeat the experiments. Only pg 51 TBARS methos: it is difficult to understand what does the author mean by sentence: "The analysis was performed at least with five samples for each material"? For TLC analyses the reference for the method is missed, and the source of the "reference solution" used for TLC - FID (producer, number) is not given. In Result and discussion part antioxidative/prooxidative capacity of studied phenolic compounds using different methods is discussed in details. However, some theoretical discussion could be given in the Theoretical chapter instead in the results and discussion chapter. Descriptions of calculations of antioxidative capacity could be given in experimental part, as it is not a result. Does the author have a theory why AOC values, obtained by the author, do not fit well with data found in literature. It can be seen in Figure 4-10 that propyl gallate reduces both the initial fast drop in dissolved oxygen concentration and slower linear oxygen uptake. Maybe the author has a "feeling" why? The author forgot to put control experiments: oxygen uptake in buffer after adding iron, Hb and oxygen uptaker in buffer adding ascorbic acid and iron. Finally, I would like to mentioned that thesis, written by Vera Kristinova, includes very important and valuable information related to the antioxidative capacity measurements.

eVSKP id 8513