Carboxymethylation of polysaccharide from Morchella angusticepes Peck enhances its cholesterol-lowering activity in rats

The chemically carboxymethylated polysaccharide (CPMEP), which is derived from the purified polysaccharide from Morchella angusticepes Peck (PMEP), was prepared. The degree of substitution of CPMEP was 0.461. Fourier transform infrared spectra analysis and ¹³C, ¹H, and DEPT135° NMR spectra indicated C6 position was partially substituted by CH₂COOH. Moreover, serum total cholesterol of hypercholesterolemic rats treated with the high dose of PMEP and CPMEP was 1.54mmol/L and 1.29mmol/L compared with that of rats fed with a 2% cholesterol diet (1.74mmol/L), respectively, indicating CPMEP had a stronger cholesterol-lowering activity than PMEP. CPMEP had a trend in reducing liver total cholesterol while increasing the excretion of total fecal and intestinal bile acids, which were probably mediated by down-regulation of hepatic 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase while up-regulation of cholesterol-7α-hydroxylase. It was therefore concluded that carboxymethylation of PMEP could enhance its cholesterol-lowering ability at least in rats.