A Sulfated Polysaccharide from the Green Alga Caulerpa taxifolia: Characteristics of Its Structure and Anti-Diabetic Activity

Polysaccharides derived from green algae have garnered significant attention owing to their distinctive structural characteristics and biological activities. In particular, sulfated polysaccharides from these algae represent a promising frontier in the discovery of novel therapeutic agents. In this present study, a sulfated galactan from <i>Caulerpa taxifolia</i>, designated SGC, was obtained by dilute alkali extraction and chromatographic purification. On the basis of chemical and spectroscopic analyses, the backbone of SGC was constituted by a backbone of →3)-β-d-Gal<i>p</i>-(1→ with sulfate substitution at the C-2 and a branch on C-6. The side chains contained →6)-β-d-Gal<i>p</i>(2SO₄)-(1→, →6)-β-d-Gal<i>p</i>(3OMe)-(1→ and →3)-β-d-Gal<i>p</i>(4,6-Pyr)-(1→ units. SGC possessed strong hypoglycemic activity in vitro, as evaluated by an assay of α-amylase inhibition. The anti-diabetic activity of SGC in vivo was further investigated using T2DM mice induced by high-fat diet combined with streptozotocin. The results indicated that SGC markedly restored body weight, reduced fasting blood glucose and possessed a significant glucose-regulating effect. Furthermore, SGC effectively increased insulin sensitivity and mitigated insulin resistance. Additionally, SGC effectively regulated lipid metabolism and alleviated oxidative stress. Notably, SGC ameliorated liver and pancreas damage induced by high-fat diet combined with streptozotocin. The investigation demonstrates that SGC is a unique sulfated galactan and has potential as a novel anti-diabetic agent.