Synthesis and physico-chemical characterization of quaternized and sulfated xylan-derivates with enhanced microbiological and antioxidant properties

Abstract

Natural polysaccharides such as xylans have attracted attention in recent years as promising substances due to their characteristics and because they are renewable sources. However, to increase their potential for application, it is important to improve some properties, achieved through modification of their structure. The purpose of this work was to synthesize, characterize and study the properties of quaternized (QXy) and sulfated xylan (SXy), produced from xylan (Xy) extracted from corn cobs. Xy presented two populations of different molecular weights and high Reducing Sugar content. Fourier Transform Infrared Spectroscopy (FTIR), Mass Spectrometry (MS), Nuclear Magnetic Resonance (1H NMR and 13C NMR) and Elementary Analysis (CHNOS) confirmed the intended synthesis modifications as new characteristics, arising from the groups introduced, were observed. Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD) showed changes in characteristics, which were induced by the modifications. Xylan modification led to an increase in its DPPH radical-scavenging activity for all concentrations tested, especially for QXy, reaching a maximum of 93.5%. Xylan modification also decreased the minimum inhibitory concentration (MIC) values for QXy, especially against Gram-positive bacteria (Staphylococcus aureus ATCC 25923), from >2.0 (Xy) to 0.25%w/v (QXy). Modified xylans present enhanced antioxidant and antimicrobial activities and the potential to be applied or incorporated in new materials for different purposes, such as biological, biomedical, packing and drug delivery formulations.