Reaction of Tetrazolium Salts with Sulfated Polysaccharides and Other Hydrocolloids

SUMMARY— Triphenyltetrazolium chloride, (TTC), selectively precipitates carrageenan and other sulfated hydrocolloids in the presence of neutral, carboxylic and phosphorylated polysaccharides. Agar is not precipitated. Tetrazolium blue (TB) precipitates both the sulfated and carboxylic polysaccharides but does not precipitate phosphorylated and neutral polysaccharides.
Except for "weak" reactions with mucin, gum karaya, sodium alginate, and polysaccharides B-1459 (NRRL); tetrazolium red, neotetrazolium chloride and tetrazolium violet precipitate only sulfated polysaccharides. Although in aqueous dispersion the proteins were not precipitated by any of the tetrazolium salts, when these salts are added to milk (containing no added carrageenan), copious precipitation occurred.
Carrageenan was isolated from milk, milk products and other complex milieu by precipitation with 2, 3, 5, -triphenyl-tetrazolium chloride. The proteins were precipitated simultaneously. The mixed carrageenan-protein precipitate was then analyzed for carrageenan by hydrolyzing it with hydrochloric acid and assaying for sulfate by the barium chloranilate method.
Mixtures of sulfated, carboxylic and neutral polysaccharides were resolved by precipitating the sulfated polysaccharide with 2, 3, Atriphenyltetrazolium chloride. After centrifugation and/or filtration to remove the precipitate, the filtrate was treated with tetrazolium blue to precipitate the carboxylic polysaccharide. The neutral polysaccharide remained in the supernatant. Solubility studies have shown that the carrageenan-TT precipitate is highly insoluble in sodium chloride, sodium sulfate, magnesium chloride and other salt solutions.
The method developed allows the use of tetrazolium salts to differentiate between and to separate the main groups (sulfated, carboxylic, and neutral) polysaccharides. After separation, the individual polysaccharides may be determined quantitatively by suitable analytical methods.