A new polysaccharide from Hawk tea: Structural characterization and immunomodulatory activity associated with regulating gut microbiota

In this study, a novel 28.6 kDa acidic polysaccharide (HTP-1), containing → 4)-GalpA-(1→, →2)-Rhap-(1 → and → 3,6)-Galp-(1 → residues as the backbone, analogous to pectin, was isolated from mature Hawk tea leaves. HTP-1 exhibited significant immunoregulatory activities on CTX-induced immunosuppressed mice in a dose-depend manner by alleviating jejunum injury and improving the levels of immune organ indexes, cytokines and immunoglobulins. Moreover, HTP-1 supplementation boosted the content of SCFAs, altered the intestinalmicrobiota composition, and raised the abundances of beneficial bacteria Muribaculaceae, Lactobacillaceae, Bacteroidaceae, Prevotellaceae and Ruminococcaceae, which showed a strong positive correlation with most immune indicators. The current findings suggested that the immunomodulatory action of HTP-1 might rely on the regulation of the gut microbiota, and these results may also serve as a foundation for the future exploitation of HTP-1 as functional foods.