Introduction
Cancer is a major health problem and is the second leading cause of death in the world.
DNA oxidation can cause mutations and can therefore play an important role in the
initiation and progression of carcinogenesis.Various antioxidants can be used to
inhibit the DNA oxidation process, which may in the first place protect the DNA and,
secondly, inhibit the formation of N-nitrosamines, which in turn ~ 80% are
carcinogenic substances.
Natural polymers (chitosan) functionalized with polyphenols can be used to prolong
these effects. Chitosan is a natural polymer that is abundant in nature. Due to its
unique biological properties, chitosan is applied in many industries.
Polyphenols are well known for their antioxidant properties, they are natural
compounds with one or more phenolic groups. In this paper, the functionalization of
chitosan with cvercitine was studied and the antioxidant properties of the obtained
composite were determined.
Materials and methods. The functionalisation of maleic anhydride to chitosan was
performed in the first step according to the figure 1:

Figure 1. The reaction mechanism of chitosan grafting to copolymer I
After purification, by copolymer I sedimentation was added in the
dimethylformamide, it was subjected to quercetin grafting according to the figure 2:

Figure 2. The reaction mechanism of chitosan grafting to copolymer II
Different methods of functionalizing chitosan with polyphenols have been studied
(figure 3). One of these methods is based on obtaining chitosan-thiosemicarbazone.
The elaborated method consists of three stages: Phase I - obtaining
thiosemicarbazone; Phase II - obtaining the chitosan-thiosemicarbazone polymer;
Phase III - the functionalization of chitosan-thiosemicarbazone with polyphenols.

Figure 3. Chitosan Functioning Mechanism with Thiosemicarbazone
Results and conclusions
The antioxidant activity of free cvercitin (Quv) and chitosan-cvercitin (Cht-Quv) was
determined. It has been established that chitosan functionalized with Quv has stronger
antioxidant activity than pure cverticin at the same concentration.
The IR and H1-NMR spectra of the thiosemicarbazone were obtained, the structure of
this intermediate was determined: (E) -methyl-2- (2-hydroxybenzylidene) hydrazine
carbodithioate or methyl-2-salicylidenehydrazine carbodithioate.
The IR spectrum of the chitosan grafted with thiosemicarbazone was analyzed and the
presence of peaks characteristic of chitosan and thiosemicarbazone and the peak at
1651 cm-1 were found to be associated therewith.
Was determined antioxidant activity by the ABTS and DPPH method. It was found
that chitosan functionalized with quercetin has stronger antioxidant activity than the
pure quercetin of the same concentration.