Sulfonated (1→6)-β-d-Glucan (Lasiodiplodan)

Abstract

Sulfonated derivatives of lasiodiplodan (LAS-S) with different degrees of substitution (1.61, 1.42, 1.02 and 0.15) were obtained and characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermal and solubility analyses. Antimicrobial, antioxidant and cytotoxic potential were also assessed. The sulfonation was confirmed by FTIR analysis with specific bands at 1250 cm–1 (S=O, strong asymmetrical stretching vibration) and at 810 cm–1 (C-O-S, symmetrical vibration associated with the C-O-SO3 group) in the sulfonated samples. SEM demonstrated that sulfonation promoted morphological changes on the surface of the biopolymer with heterogeneous fibrillary structures appearing along the surface following chemical modification. LAS-S showed high thermal stability, with mass loss due to oxidation at temperatures close to 460 °C. Sulfonation increased the solubility of LAS, and in addition, increased the antimicrobial activity, especially against Candida albicans (fungicidal) and Salmonella enterica Typhimurium (bacteriostatic). Native lasiodiplodan (LAS-N) showed higher OH˙ removal capacity, while LAS-S had higher ferric ion reducing antioxidant power (FRAP) potential. LAS-N and LAS-S did not demonstrate lethal cytotoxicity against wild and mutant strains of Saccharomyces cerevisiae. Samples with higher degree of substitution (1.42 and 1.61) showed lower potential to induce oxidative stress.

Engineered Sulfated Polysaccharides for Biomedical Applications

“…[ 23 ] Several studies employ a pyridine salt intermediate ( Figure ), which can catalyze the sulfation reaction and potentially reduce degradation and other side reactions from heating with strong acids alone. [ 24,25 ] Certain sulfation procedures also start with forming a tetrabutylammonium salt of the polysaccharides to improve solubility in organic solvents. [ 26 ] These procedures target primary hydroxyl (OH) groups, whereas selective N‐sulfation has been demonstrated primarily on N ‐acetyl‐glucosamine‐containing polysaccharides such as chitosan Chit, [ 27 ] HA, [ 28 ] and heparin/HS derivatives [ 29 ] using trimethylamine/triethylamine‐sulfur trioxide.…”

“…Proposed reaction mechanism of sulfation of a glucose (Glc)‐based polysaccharide with chlorosulfonic acid and a pyridine salt intermediate. [ 25 ] …”

“…[23] Several studies employ a pyridine salt intermediate (Figure 2), which can catalyze the sulfation reaction and potentially reduce degradation and other side reactions from heating with strong acids alone. [24,25] Certain sulfation procedures also start with forming a tetrabutylammonium salt of the polysaccharides to improve solubility in organic Figure 2. Proposed reaction mechanism of sulfation of a glucose (Glc)-based polysaccharide with chlorosulfonic acid and a pyridine salt intermediate.…”

“…Proposed reaction mechanism of sulfation of a glucose (Glc)-based polysaccharide with chlorosulfonic acid and a pyridine salt intermediate. [25] solvents. [26] These procedures target primary hydroxyl (OH) groups, whereas selective N-sulfation has been demonstrated primarily on N-acetyl-glucosamine-containing polysaccharides such as chitosan Chit, [27] HA, [28] and heparin/HS derivatives [29] using trimethylamine/triethylamine-sulfur trioxide.…”

“…[157] Recently, researchers sulfated a 1→6-linked fungal β-glucan (DS = 0.2) and reported growth inhibiting properties of the sulfated polysaccharides against selected Gram-negative bacteria and yeast compared with the nonsulfated control. [25] In a different study 1→3-linked β-glucans were sulfated (DS = 0.9), resulting in improved solubility and antimicrobial properties against multiple bacterial strains with an MIC in the range of 1-5 mg mL −1 . [158] Sulfated dextrans (sDex) have been demonstrated to block proteoglycan-medicated cell attachment of both gram negative and positive bacteria within the genera Helicobacter, [159] Staphylococci, [160] and Borrelia.…”