Abstract
Hydroxyethyl starch (HES) was studied concerning the relationships between its physicochemical properties and biological activities to obtain the most desirable plasma expander. Since degree of substitution (DS) had been clarified to have influences on the biological activities, the molecular weight was then examined with designing DS in the constant range of 0.43-0.55. After infusion of 15 ml/kg of 6% HES solution in saline into rabbits, persistence of polysaccharides in blood was determined. HES with higher molecular weight was more persistent when DS was identical. The molecular weight, however, had little influences on the amount of formed reducing sugars when resistance against pig pancreas α-amylase was tested in vitro. HES with DS 0.54 and molecular weight about 216000 was hydrolyzed with various concentrations of HCl, and the physicochemical properties and the biological activities of the hydrolysates were also examined. Comparing the lowering tendency of the viscosity with the amount of formed reducing sugar and from the gel filtration patterns of the hydrolysates, it was assumed that the hydrolysis of HES with HCl resulted in separation to two or more intermediate lower molecular weight polysaccharides besides the reducing sugar liberation. Mode of hydrolysis was partly discussed in connection with stability of HES in blood.
