Assessment of biochemical and immunomodulatory activity of sulphated polysaccharides from Ulva intestinalis

• Sulphated polysaccharides from U. intestinalis fractionated on a silica-silica column activated macrophages.
• The molecular weight and sulphate/total sugar ratio affect the immunomodulatory activity of sulphated polysaccharides.
• Fractionated sulphated polysaccharides showed higher scavenging activity and immunomodulatory activity than unfractionated sulphated polysaccharides.

The biochemical characteristics and immunomodulatory activity of sulphated polysaccharides isolated from Ulva intestinalis and fractionated using a silica-silica column were investigated. The unfractionated (USP) and fractionated sulphated polysaccharides (FSP4, FSP30, and FSP32) consisted mostly of carbohydrates (4.84–26.55%) and sulphates (2.85–20.42%). Structural analyses showed that USP, FSP4, FSP30 and FSP32 had molecular weights of 300, 80, 110 and 140 kDa, respectively. FSP30 exhibited the strongest DPPH radical scavenging activity. Moreover, FSP30 showed stronger immunomodulatory activities than UPS in term of stimulating the production of pro-inflammatory cytokines, including nitric oxide (NO), tumour necrosis factor-α (TNF-α), and interleukin-1β (IL-1β), in macrophage J774A.1 cells. USP and FSP30 were not cytotoxic to mouse macrophage at the tested concentrations (6.25–50 μg/mL). The results suggested that U. intestinalis polysaccharides could be explored as potential antioxidant and immunomodulatory agents to be used as complementary medicine or functional foods.