Hypoglycemic action of semipurified fractions from hot-water extracts of the submerged-culture broth of Agaricus blazei Murill was examined in
streptozotocin (60 mg/kg, intraperitoneal)-induced diabetic male Sprague-Dawley rats, relative to the diabetes
drug metformin. The hot-water extract, treated with
ethanol to remove
beta-glucans and
glycoproteins, was freeze-dried, and fractionated into
hexane,
chloroform,
ethyl acetate (EA), and
butanol fractions. The EA fraction (EAF; 200 mg/kg
body weight) reduced (p < 0.05) the
blood glucose level in the oral
glucose tolerance test, relative to the other fractions and control. In a 14 day-treatment study, diabetic rats treated with the EAF displayed a suppressed
blood glucose level and elevated plasma
insulin and
glucose transport-4
proteins; the reactions occurred in a dose-dependent manner (200 and 400 mg/kg
body weight) compared to those in control animals. The EAF reduced the levels of
triglyceride and
cholesterol in plasma, the activity of
glutamate-
oxaloacetate transaminase and
glutamate-
pyruvate transaminase in blood, and the content of
thiobarbituric acid reactive substance in the liver and kidney. The
hypoglycemic efficacy of the EAF (400 mg/kg
body weight) was similar to that of
metformin (500 mg/kg
body weight). The EAF contained substantial amounts of isoflavonoids including
genistein,
genistin,
daidzein, and
daidzin, which could have contributed to the fraction's
hypoglycemic action. These results indicate that the hot-water extract of the submerged-culture broth of Agaricus blazei contains an EAF having potent
hypoglycemic action, which could be useful in the treatment of
diabetes mellitus.