A new in vitro assay of cholesterol adsorption by food and microbial polysaccharides

The adsorption of total cholesterol by polysaccharides was measured in vitro by enzymatic reactions, including the polysaccharide precipitation procedure. Total cholesterol adsorption capacities, in a mixture of polysaccharide and total cholesterol, were compared for apple pectin, gelrite gellan gum, xanthan gum, high-methoxyl pectin, citrus pectin, high-viscous alginate, low-viscous alginate, dextran, and zooglan. Acidic polysaccharides such as pectins, alginate, and xanthan gum at concentrations of 0.1% (wt/vol) were able to adsorb over 90% of the total cholesterol when dissolved in distilled water, sodium acetate buffer (pH 4.6), or sodium phosphate buffer (pH 7.0). However, total cholesterol adsorptions by gellan and zooglan were dependent upon the salt concentration and pH value, which decreased cholesterol adsorption in the following order by degree: distilled water, acidic pH, and alkaline pH. In particular, total cholesterol adsorption of zooglan was greatly decreased by the addition of sodium chloride. With 0.1% (wt/vol) polysaccharide dissolved in distilled water, the adsorption capacities of alginate, pectins, gellan gum, xanthan gum, and zooglan were 2.9, 2.88, 2.5, 2.9, and 2.4 mg/dL, respectively. However, 0.2% of zooglan was able to completely adsorb the cholesterol (3 mg/dL), whereas dextran did not adsorb cholesterol at all, producing no precipitate with hexadecyltrimethylammonium bromide.