Photoelectrocatalytic pretreatment enhances NMR spectral quality of sulfated polysaccharides over acid degradation

Although nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical tool, obtaining high-resolution NMR spectra of some high-molecular-weight and viscous polysaccharides remains challenging. Partial degradation could facilitate polysaccharides for NMR analysis, but potential composition alterations raise concerns, especially for sulfated polysaccharides. To explore the applicability of degradation approaches for sulfated polysaccharides, the present study compared outcomes of acid (HCl) and photoelectrocatalysis pretreatments for depolymerizing 2 representative sulfated polysaccharides, carrageenan and fucoidan. The results revealed that 1 M HCl at 100 °C could efficiently depolymerize carrageenan to 20 kDa within 30 min and fucoidan to 30 kDa within 10 min, but destruct more than half of sulfated polysaccharides. In contrast, photoelectrocatalysis could generate low-molecular-weight products while preserving structure blocks. Notably, both depolymerization pretreatments could facilitate sulfated polysaccharides for NMR analysis and enhance the spectral resolution. However, HCl tended to produce mono- and oligo-saccharides thereby affecting NMR spectra, while 50-min and 60-min photoelectrocatalysis treatments were suitable for carrageenan and fucoidan, respectively, to improve their NMR spectra without signal alterations. Therefore, the present study demonstrated photoelectrocatalysis depolymerization as a potential pretreatment for sulfated polysaccharides to facilitate their NMR analysis.