Comparative study of the hypocholesterolemic and hypolipidemic activity of alginate and amidated alginate in rats

Alginate is a copolymer of β-d-mannuronate and α-l-guluronate, which are present in the cell wall of brown algae. The hypocholesterolemic and hypolipidemic activities of alginate and its derivative, which is prepared by a reaction with octadecylamine, were compared in rats fed diets containing cholesterol and palm fat at 10 and 50 g/kg, respectively. Amidated alginate at 20 g/kg significantly decreased serum cholesterol from 2.93 to 2.00 μmol/mL, serum triacylglycerols from 1.66 to 0.92 μmol/mL, hepatic cholesterol from 17.5 to 5.9 μmol/g, and total hepatic lipids from 67.4 to 51.7 mg/g. Alginate at 20 g/kg significantly reduced hepatic cholesterol to 13.1 μmol/g, but did not influence serum cholesterol, triacylglycerols, and total hepatic lipids. Amidated alginate significantly increased the faecal concentrations of neutral sterols from 98.7 to 122.4 μmol/g DM, but decreased faecal concentration of bile acids from 19.4 to 14.0 μmol/g DM. In samples of intestinal contents, taurine-conjugated bile acids dominated glycine conjugates. The supplementation of diets with cholesterol significantly increased the expression of hepatic cholesterol 7α-hydroxylase, especially in rats that received cholesterol without alginate or amidated alginate. In conclusion, amidated alginate is an effective hypocholesterolemic agent that is more efficient than its parent polysaccharide.