Structural characterization and alleviating function of the polysaccharide SGF-2 from Sargassum graminifolium on Ovalbumin-induced food allergy in mice by up-regulating immunosuppression
s Food allergy (FA) has emerged as a pivotal concern for food safety and public health worldwide. Among marine-derived nutrients, fucoidans have shown promising anti FA potential, yet the absence of studies on well-defined fucoidan structures has made it quite challenging to establish a clear relationship between their structure and anti-allergic activity. Our previous studies demonstrated that crude fucoidan from Sargassum graminifolium substantially ameliorated FA symptoms and further isolation yielded a S. graminifolium fucoidan SGF-2. Nevertheless, its structural characteristics and anti FA properties remain elusive. In this study, we elucidated the major backbone linkages of SGF-2 via methylation analysis combined with nuclear magnetic resonance (NMR) spectroscopy and evaluated its anti FA potential in an ovalbumin (OVA)-sensitized mouse model. The results showed that SGF-2 intervention effectively mitigated FA symptoms by markedly reducing OVA-specific Immunoglobulin E (IgE) and related cytokines levels, decreasing the incidence of diarrhea and the spleen index, and suppressing intestinal inflammation. 16S_rRNA sequencing analysis demonstrated that SGF-2 interventions could effectively counteract gut microbiota disruption induced by FA by partially enhancing microbial community diversity, augmenting the relative abundances of probiotics that produce short-chain fatty acids (SCFAs), and suppressing the relative abundances of harmful bacteria. Furthermore, the levels of SCFAs in feces increased following interventions with SGF-2. Flow cytometry analysis revealed that SGF-2 reversed the imbalance of Th1/Th2 polarization, particularly by inhibiting the Th2-type immune response and promoting the differentiation of Regulatory T cells (Tregs). These findings suggest that fucoidan derived from S. graminifolium holds great promise for the development of functional foods.
危险品化学品经营许可证（带存储）