Stabilnost hlorofila na oksidacioni stres u vodenom medijumu i u lipozomima
Author
Petrović, SanjaMentor
Zvezdanović, JelenaCommittee members
Anđelković, TatjanaCvetković, Dragan

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The stability of chlorophyll on chosen oxidative stresses in disorganized aqueous
medium and more organized liposomal structures is a topic of this doctoral thesis. The unique
role of chlorophyll, based on its specific and very diverse chemical reactivity justifies its
application in industrial technologies, food processing and pharmaceutical and cosmetic
industry as well as in medicine. The question about chlorophyll stability is set as one of the
preconditions for its potential applications in various areas of science and technology. In vitro
oxidative stresses applied to the chlorophyll are: chemical oxidation by Fenton reagent and
thermal initiator, enzyme catalyzed oxidation and photo-oxidation by continuous visible and
UV-B irradiation. The stability of chlorophyll in the aqueous medium after oxidative stress
was studied using absorption spectroscopy while the corresponding changes in the structure
of Chl-molecules was followed by electro-spray mass spectrometry combined with UHP...LC
chromatography, in order to get the possible insight into the degradation-oxidation
mechanisms. Changes in the physical conditions of the liposome interior (organized lipid
structures), which affect the behavior of incorporated chlorophyll penetration and therefore a
different degradation degree, were investigated using absorption and fluorescence
spectroscopy. In addition to the presented methods, in order to evaluate some of the possible
mechanisms involved in oxidative stress, two peroxide tests were performed: test of
conjugated dienes and TBA-MDA test.
The results show that the stability of chlorophyll depends not only on chlorophyll
concentration but also the nature of the applied oxidative stress. Generally, the chlorophyll in
liposomes, the same as in the aqueous medium, shows a low stability degree, which resulted
in its modifications, creating oxidation-degradation products. The destructiveness of the
applied oxidative stresses on chlorophyll could be ranked as follows: the effect of Fenton
reagent < effect of the thermal initiator < VIS < UV-B radiation, at precisely defined
conditions. Chlorophyll is more stable in liposome dispersions, which supports the
conclusion that it is better to keep it in liposomes than in water.
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Based on these results it can be concluded that the more accurate knowledge of the
chlorophyll behavior under the oxidative stress, as well as its optimal concentration and
stability in the potential formulations, is crucial to its further use.