Physicochemical Characterization of Sulfated Polysaccharides from the Thermophilic Cyanobacterium Leptolyngbya sp. CIN61 and Their Antimicrobial and Anti‐Proliferative Activities

In the present study, sulfated polysaccharides (SPSs) were isolated from the thermophilic cyanobacterium Leptolyngbya sp. CIN61 was characterized and evaluated for its in vitro antimicrobial and anticancer activities. The SPSs were composed of 71.4% sugars, 17% proteins, and 7.9% sulfates. The monosaccharide composition determined by high-performance liquid chromatography with a refractive index detector revealed the presence of rhamnose, arabinose, mannose, glucose, and galactose. Structural characterization using Fourier-transform infrared spectroscopy, ¹H nuclear magnetic resonance, and correlated spectroscopy confirmed the presence of peptide groups, uronic acids, sulfate groups, and acetylated hexosamine residues. Atomic force microscopy revealed a wave-like microstructure with irregular, rough surface features while scanning electron microscopy showed uneven, smooth tubular structures with varying shapes, sizes, and orientations. In in vitro bioactivity assays, the SPSs exhibited selective antifungal activity against Aspergillus niger and inhibited the proliferation of colorectal adenocarcinoma DLD-1 cells, with an IC₅₀ value of 4.73 mg/mL. These findings suggest that thermophilic Leptolyngbya sp. is a promising source of SPSs with potential for various industrial applications.