Alkali-extracted rhamnogalactoarabinan from Chaetomorpha linum: Characterisation and anti-type 2 diabetic effect

Sulphated galactoarabinans, extracted from members belonging to the Cladophoraceae (Chlorophyceae) family, have been reported to have potential as novel anti-diabetic agents. However, relatively few studies have investigated this research topic. In the present study, a water-soluble polysaccharide designated CBS2 was obtained from Chaetomorpha linum using dilute alkaline solution, preparative anion exchange, and size-exclusion chromatography. Chemical and high-performance liquid chromatography analyses revealed that CBS2 is a sulphated rhamnogalactoarabinan. Gas chromatography-mass spectrometry and nuclear magnetic resonance analyses revealed that the backbone of CBS2 was primarily made up of 4-linked β-L-arabinopyranose, which was sulphated at C-2/C-3. The branches were primarily composed of 4-linked-β-d-galactopyranose and positioned at C-3 of 4-linked β-L-arabinopyranose. Transmission electron microscopy and thioflavin T fluorescence experiments showed that CBS2 successfully suppressed human islet amyloid polypeptide (hIAPP) aggregation in vitro. In NIT-1 cells, CBS2 reduced hIAPP-induced cytotoxicity. CBS2 markedly lowered the production of intracellular reactive oxygen species and oxidative stress induced by hIAPP aggregation in NIT-1 cells. In addition, CBS2 co-localised with mitochondria and protected mitochondrial function from hIAPP aggregation-induced damage by stabilising the mitochondrial membrane potential. These data suggest that CBS2 may potentially serve as an anti-diabetic agent for the treatment of type 2 diabetes mellitus.