Physicochemical properties, antioxidant and antibacterial activities of dialdehyde microcrystalline cellulose

A series of dialdehyde microcrystalline cellulose (DAMC) were prepared by NaIO₄ oxidation of microcrystalline cellulose (MCC), and their physico-chemical properties, antioxidant activity, and antibacterial activity were further investigated. The results of scanning electron microscopy indicated that the particle size of DAMC became shorter than that of unoxidized MCC, and the surface erosion of particles was observed. The degree of crystallinity and thermal stability of DAMCs decreased as their aldehyde contents increased. The formation of aldehyde and hemiacetal groups of the DAMC was confirmed by Fourier transform infrared spectroscopy spectra. The antioxidant activity assays demonstrated that the DAMC with 6.59 mmol/g of aldehyde content showed the highest scavenging effect on DPPH, ABTS, and hydroxyl radicals with half-inhibitory concentration (IC₅₀) values of 5.9, 5.6 and 8.1 mg/mL; its reducing power was also the best among the three samples. The antimicrobial activity test results showed that DAMCs with high aldehyde contents (more than 5.14 mmol/g) exhibited the strongest antibacterial activity against S. aureus, B. subtilis, E. coli and S. typhimurium, and their MIC values were 15, 15, 15, and 30 mg/mL, respectively. Our results proved that the physico-chemical properties of DAMC may have great influence on its antioxidant and antibacterial capacities.