The effect of NaOH and NaClO/NaBr modification on the structural and physicochemical properties of dextran

Dextran is a polysaccharide with a high medicinal value. Thus, the chemical modifications of dextran, and the structural and physicochemical properties of its derivatives should be given focus. Dextran (Mw 5000 Da to 7500 Da) can complex with iron. In this study, dextran (Mw 5400 Da) was modified at different pH levels (8–14) by using NaOH and NaClO/NaBr. The carboxyl groups of the modified dextran were determined using infrared spectroscopy, and the carboxyl contents were compared. The results of high-performance liquid chromatography indicated that dextran was degraded during the modification. The crystallization and the structure of the carboxyl-modified dextran were investigated using X-ray diffraction, nuclear magnetic resonance, and quadrupole time-of-flight mass spectrometry. The physicochemical properties, i.e., solubility, and granule morphology, of the carboxyl-modified dextran were carefully characterized and compared. This work provides a theoretical foundation for the accurate selection of carboxyl-modified dextran and the development of a novel strategy for the preparation of metal complexes.