Structural analysis of immunostimulating sulfated polysaccharides from Ulva pertusa

Area of Science:

• Marine natural products chemistry
• Carbohydrate chemistry
• Immunology

Background:

• Seaweed-derived sulfated polysaccharides are known for diverse biological activities, including immunomodulation.
• Ulva pertusa is a marine alga with potential for bioactive compound discovery.
• Understanding the structure-activity relationship of these polysaccharides is crucial for their application.

Purpose of the Study:

• To extract and fractionate sulfated polysaccharides from Ulva pertusa.
• To determine the detailed structure, including glycosidic linkages and sulfation patterns, of the most immunostimulating fraction.
• To investigate the stability of the polysaccharide backbone during desulfation.

Main Methods:

• Extraction and fractionation of sulfated polysaccharides from Ulva pertusa.
• Chemical modifications including reduction and desulfation using methanol as a sulfate acceptor.
• Structural elucidation using Gas Chromatography-Mass Spectrometry (GC-MS) and 2D-Nuclear Magnetic Resonance (2D-NMR) spectroscopy.

Main Results:

• The most immunostimulating fraction (F(2)) was isolated.
• Desulfation at 120°C removed 90.1% of sulfates without significant backbone degradation.
• The polysaccharide backbone primarily consists of α-(1→4)-L-rhamnopyranosyl, β-(1→4)-D-glucuronosyl, β-(1→2)-L-rhamnopyranosyl, and β-(1→4)-D-xylopyranosyl residues, with branching at the O-2 position of rhamnose. Sulfate groups are predominantly located at the O-3 position of glucuronic acid.

Conclusions:

• The structural characterization of the immunostimulating fraction from Ulva pertusa was successfully achieved.
• The specific arrangement of sugar residues and sulfate groups contributes to the observed immunostimulatory activity.
• The findings provide a basis for further research into the pharmacological applications of Ulva pertusa polysaccharides.