Preparation of low-molecular-weight fucoidan via TEMPO/NaClO/NaBr-mediated oxidative degradation under alkaline conditions

TEMPO/NaClO/NaBr is applied to controlled degradation of fucoidan. • TEMPO/NaClO/NaBr enables efficient LMWF production from fucoidan in 0.5 h. • Galactose changes are consistent with possible C6 oxidation under TEMPO mediation • The TEMPO-free system caused 18.97% fucose loss and 6.13% sulfate loss. Low-molecular-weight fucoidan (LMWF) is highly desirable for food and pharmaceutical applications, yet conventional degradation methods often compromise its bioactive sulfate content. In this study, we employed a TEMPO/NaClO/NaBr system to degrade fucoidan under mild alkaline conditions and systematically investigated the degradation kinetics, structural changes, and anticoagulant activity of the resulting LMWF products. The degradation process was monitored by NaOH consumption and molecular weight distribution analysis. The optimal reaction time was determined to be 0.5 h, during which the molecular weight decreased from 337.4 kDa to 24.3 kDa, yielding LMWF with a relatively narrow molecular weight distribution (PDI = 1.08). Structural characterization by monosaccharide composition analysis, FT-IR, and 1 H NMR suggested that TEMPO-mediated oxidation favored oxidation at C6 primary hydroxyl groups, as indicated by changes in galactose and galacturonic acid contents, while no significant loss of total sulfate content was observed. In contrast, the non-selective NaClO/NaBr system caused substantial losses of fucose (18.97%) and total sulfate content (6.13%). Notably, the TEMPO-derived LMWF retained potent anticoagulant activity in the APTT assay while exerting a minimal effect on the PT pathway, suggesting a potentially lower bleeding risk. This study provides a promising strategy for the controlled preparation of LMWF with minimal loss of total sulfate content and a potentially favorable safety profile. Download: Download high-res image (175KB) Download: Download full-size image