Shang-Cheng Hung
Journal of the American Chemical Society
August 28, 2025

Green algae, commonly used as a source of food nutrients, contain ulvan, which is a water-soluble sulfated heteropolysaccharide isolated from Ulva. Ulvan exhibits a range of biological properties, including antitumor, antiviral, anticoagulant, and immunomodulatory activities. Its sugar backbone consists of 1→4-linked disaccharide repeating units, which are categorized as ulvanobiuronic acids (types A_3′S and B_3′S) and ulvanobioses (types U_3′S and U_2S3′S). Despite its promising therapeutic potential, the detailed structure–activity relationship of ulvan remains unclear. In this study, an efficient strategy was developed, utilizing orthogonally protected α1→4-linked l-Rha-d-Glc, l-Rha-l-Ido, and l-Rha-d-Xyl derivatives as disaccharide building blocks to synthesize di-, tetra-, hexa-, and octasaccharides of types A_3′S, B_3′S, and U_3′S. The immunomodulatory effects of these compounds were evaluated through cytokine induction experiments. The results revealed that only the B_3′S and U_3′S octasaccharides had a significant influence on the gene expression of IL-1β, IL-6, IL-10, GM-CSF, and G-CSF. This chemical glycobiology approach offers valuable insights into the biomedical applications of marine ulvan oligosaccharides.

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