The Nutritional Biochemistry of Chromium(III) - Survival-training.info

Introduction: A history of chromium studies (1955–1995) 5test. The material was also found to be comprised of at least six amino acids tentativelyidentified as leucine or isoleucine, proline, valine, alanine, serine, and either glutamic oraspartic acid. The material when administered orally to rats (2 ng Cr) resulted in betterchromium absorption than when chromic chloride was given [17].Mertz and coworkers reported the details of the isolation of Brewer’s yeast “GTF”in 1977 nearly 20 years after the initial report [18]. Brewer’s yeast was extracted withboiling 50% ethanol. The ethanol was removed under vacuum, and the aqueous residualwas applied to activated charcoal. Material active in bioassays (vide infra) was elutedfrom the charcoal with a 1:1 mixture of concentrated ammonia and diethyl ether. Afterremoval of the ammonia and ether under vacuum, the resulting solution was hydrolyzedby refluxing for 18 hours in 5 M HCl. Finally, the HCl was removed under vacuum,the solution was extracted with ether, and the pH of the solution was adjusted to 3. Thecationic orange-red material was further purified by ion exchange chromatography [18].Unfortunately, these incredibly harsh conditions would have destroyed any proteins orpeptides or nucleic acids that initially could have been associated with the chromium.Thus, the cases that the form of chromium recovered after the treatment resembles theform in the yeast are remote at best.The isolated “GTF” possessed a distinct feature at 262 nm in its ultravioletspectrum, while mass spectral studies (no data presented) indicated the presence of apyridine moiety [18]. This led to the identification of nicotinic acid as a componentof “GTF”; nicotinic acid was sublimed from the material (no experimental informationgiven) and identified by extraction with organic solvents (no data presented). Aminoacid analyses indicated the presence of glycine, glutamic acid, and cysteine as well as otheramino acids, although the relative amounts were not reported. The results were interpretedto indicate that “GTF” was a complex of Cr, nicotinate, glycine, cysteine, and glutamate.The properties of “GTF” were compared to those synthetic complex(es) preparedfrom Cr 3+ and nicotinic acids and the above-mentioned amino acids [18]. The materialwas found to possess an approximate composition of 1 Cr:2 nicotinate:2 glycine:1 glutamate:1cysteine, but these components only accounted for 88% of the material. The syntheticmaterial and the material from Brewer’s yeast behaved similarly upon ion exchangeand size exclusion chromatography (unfortunately no estimate of molecular weight wasgiven), as the major component of each coeluted. In paper chromatography experiments,the materials gave several bands; only one from each material was active in the bioassaysand migrated with the same R f value. The chromium in these active bands represented11 and 6% of the total chromium for the synthetic and Brewer’s yeast materials, respectively.The synthetic material and the yeast material possessed similar ultraviolet andinfrared spectra [18]. Interpretation of this work is nearly impossible. Characterizationof bulk materials of which only a tiny minority is active does not allow for clearlydeciphering the composition of the active component(s). Thus, one cannot assume thatthe amino acid analysis of the bulk product reflects the “active” component. Because ofthe destructive isolation procedure used to obtain the chromium material from Brewer’syeast (that destroyed proteins from which the observed amino acids were probably generatedand also contained conditions under which nicotinate could have been chemicallygenerated from other compounds), the nature of the form of chromium in Brewer’s yeastwas not successfully determined. The orange-red color associated with both materials isalso notable and could suggest that ammonia is present as a chromium ligand.