One of the approaches to increase bioavailability and stability of hydrophobic biologically active compounds is their incorporation into polymer backbone. This work deals with the modification of chitosan (CS) with gossypol (GS), a phenolic compound with confirmed anticancer properties, by the free-radical grafting method. The series of the CS derivatives with increasing content of GS were prepared using pure GS or gossypol acetate (GSA) and compared to the control CS (cCS). The starting CS, cCS, and GS-containing derivatives were characterized using Fourier-transform infrared (FTIR), Raman, and 13C ssNMR spectroscopies; elemental and thermogravimetric analysis to evaluate the influence of the radicals and GS on the properties of polymers was performed. The Folin-Ciocalteu (F-C) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods were used to evaluate antioxidant properties of GS-modified CSs. Additionally, the polymer solubility and the specific viscosity of the solutions were determined. The content of GS in polymers raised proportionally with increasing amount of GS added to the reaction mixture, thereby enhancing the ability to scavenge free radicals. The type of GS used (GS or GSA) in polymers affected the degree of CS crosslinking (higher for pure GS), polymer solubility (lower for pure GS), the amount of grafted GS (~20% higher for GSA), and antioxidant properties in favor of GSA.

CEISAM Institute UMR 6230 CNRS Nantes University F 44000 Nantes France

Department of Polymer Particles Institute of Macromolecular Chemistry Czech Academy of Sciences Heyrovského nám 2 162 00 Prague Czech Republic

Faculty of Chemistry Jagiellonian University Gronostajowa 2 30 387 Krakow Poland

Faculty of Science Charles University Albertov 2038 128 00 Prague Czech Republic

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