Separation of biologically active chromium complex from cow colostrum.

By a procedure based on ion-exchange chromatography, five chromium-containing fractions were separated from the ethanol extract (50-90%) of cows' colostrum which should provide infant with all or most of the chromium needed in available form. Three of the fractions are anionic (A-1, A-2 and A-3) and two are cationic (C-1 and C-2). Two major fractions, A-1 and A-3, comprise together about 77% of the total chromium recovered in the effluent after ion-exchange chromatography and C-1 and C-2 comprise together only about 21%. Approximate molecular weight was determined by the Sephadex gel chromatography to be 1,500 for A-1 and C-2 and 2,000 for C-1. A-3 was eluted from the Sephadex gel column at the elution position corresponding to that of inorganic trivalent chromium. Among five fractions, A-1 shows glucose tolerance factor (GTF) activity as measured by the stimulation of [U-14C] glucose oxidation to 14CO2 in rat epididymal adipocytes. A-1 stimulates glucose oxidation at chromium concentration as low as 100 pg/ml only when it is incubated with insulin. These findings suggest that A-1 fraction separated from cow milk contains a low-molecular-weight, chromium complex which plays a role in glucose metabolism in close relation with the action of insulin.