Cholesterol-lowering activity of various undigested fractions of soybean protein in rats.
The undigested high-molecular-weight fraction (HMF) of soybean protein prepared after exhaustive digestion by microbial proteases significantly decreased serum cholesterol levels to approximately 45% (p less than 0.05) of those observed with the parent protein in rats fed diets containing cholesterol (0.5%) and sodium cholate (0.125%). HMF bound conjugated bile salts in vitro and significantly increased fecal excretion of both neutral and acidic steroids by 65-95% and 80-170% more, respectively (p less than 0.05), than did the intact protein. Extraction of HMF with methanol slightly decreased the activity, but the methanol-soluble fraction was not regarded as a principal determinant. Soybean saponin at the dietary level equivalent to that contained in HMF did not effectively lower serum cholesterol. The activity was not necessarily duplicated even when methanol-treated fractions were recombined. Further degradation of the methanol-extracted HMF by various proteases resulted in loss of activity. HMF obtained after pepsin digestion exerted a potential similar to that of HMF prepared after digestion by microbial proteases.
Laboratory of Nutrition Chemistry, Kyushu University School of Agriculture, Fukuoka, Japan.
M
M
Sugano
S
S
Goto
Y
Y
Yamada
K
K
Yoshida
Y
Y
Hashimoto
T
T
Matsuo
M
M
Kimoto
D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism; D002784:Cholesterol / Q000032:analysis / Q000097:blood*; D004044:Dietary Proteins / Q000378:metabolism / Q000494:pharmacology*; D008055:Lipids / Q000032:analysis / Q000097:blood; D008099:Liver / Q000032:analysis; D008297:Male; D000432:Methanol / Q000494:pharmacology; D010940:Plant Proteins / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012503:Saponins / Q000494:pharmacology; D013025:Glycine max; D014280:Triglycerides / Q000032:analysis / Q000097:blood; D015430:Weight Gain
D001647:Bile Acids and Salts; D004044:Dietary Proteins; D008055:Lipids; D010940:Plant Proteins; D012503:Saponins; D014280:Triglycerides; D002784:Cholesterol; D000432:Methanol