Kreatin etyl ester (CEE) konverteres mer eller mindre umiddelbart til kreatinin (ikke bra) i sure miljøer (som i magesekken), og rekker dermed ikke å gjøre det et kreatintilskudd skal; nemlig å øke nivåene av kreatin i musklene.
Spillane et al, 2009: nivåene av kreatin i serum (blodet) etter tilførsel av placebo (PLA), kreatin monohydrate (CRT) eller kreatin etyl ester (CEE):
Nivåene av kreatin i musklene etter tilførsel av placebo (PLA), kreatin monohydrate (CRT) eller kreatin etyl ester (CEE):
Nivåene av
kreatinin i serum etter tilførsel av placebo (PLA), kreatin monohydrate (CRT) eller kreatin etyl ester (CEE):
Link til studien:
http://www.jissn.com/content/6/1/6Giese og Lecher, 2009:
"There are a number of forms of creatine available that attempt to improve the solubility and permeability, with the anticipation this will result in an improved pharmacokinetic profile and ultimately an enhanced ergogenic response. Previous research has shown that the different salt forms can improve solubility resulting in slightly altered pharmacokinetic profiles, however specific data exploring the conversion of esterified derivatives to creatine is lacking. The purpose of this study was to examine the assertion that creatine ethyl ester undergoes enzymatic conversion to creatine in human tissues. The IN VITRO response of creatine ethyl ester to incubation in human plasma was examined by H-NMR analysis. Lyophilized human plasma was reconstituted in D2O and phosphate-buffered saline and 1.5 mg of the analyte was added. Following incubation at 37 degrees C for 4 h and subsequent protein precipitation, the supernatant was analyzed by NMR, utilizing the diagnostic chemical shift of the methylene signal to determine the species present in solution, I.E. creatine ethyl ester, creatine, or creatinine. Both creatine and creatinine were run in parallel as control experiments and each assay was run in triplicate. As expected both creatine and creatinine remained unchanged. However, conversion of creatine ethyl ester to creatine by the esterases in human plasma was not observed to any detectable extent and the only species detected after the incubation period was creatinine. While not a definitive characterization of the IN VIVO behavior, these results strongly warrant a complete IN VIVO pharmacokinetic analysis of creatine ethyl ester since it appears these "pronutrients" may actually provide large exogenous sources of pharmacologically inactive creatinine rather than ergogenic creatine."
http://www.ncbi.nlm.nih.gov/pubmed/19585404
"Creatine ethyl ester was incubated at 37 degrees C in both water and phosphate-buffered saline and the diagnostic methylene resonances in the (1)H NMR spectrum were used to identify the resultant products. It was found that mild aqueous conditions result in the cyclization of creatine ethyl ester to provide inactive creatinine as the exclusive product, and this transformation becomes nearly instantaneous as the pH approaches 7.4. This study demonstrates that mild non-enzymatic conditions are sufficient for the cyclization of creatine ethyl ester into creatinine, and together with previous results obtained under enzymatic conditions suggests that there are no physiological conditions that would result in the production of creatine. It is concluded that creatine ethyl ester is a pronutrient for creatinine rather than creatine under all physiological conditions encountered during transit through the various tissues, thus no ergogenic effect is to be expected from supplementation."
http://www.ncbi.nlm.nih.gov/pubmed/19660433
Katseres et al, 2009:
"The rate of the non-enzymatic hydrolysis of creatine ethyl ester (CEE) was studied at 37 degrees C over the pH range of 1.6-7.0 using (1)H NMR. The ester can be present in solution in three forms: the unprotonated form (CEE), the monoprotonated form (HCEE(+)), and the diprotonated form (H(2)CEE(2+)). The values of pK(a1) and pK(a2) of H(2)CEE(2+) were found to be 2.30 and 5.25, respectively. The rate law is found to be Rate=-dCCEE/dt=k++[H2CEE2+][OH-]+k+[HCEE+][OH-]+k0[CEE][OH-] where the rate constants k(++), k(+), and k(0) are (3.9+/-0.2)x10(6)L mol(-1)s(-1), (3.3+/-0.5)x10(4)L mol(-1)s(-1), and (4.9+/-0.3)x10(4)L mol(-1)s(-1), respectively. Calculations performed at the density functional theory level support the hypothesis that the similarity in the values of k(+) and k(0) results from intramolecular hydrogen bonding that plays a crucial role. This study indicates that the half-life of CEE in blood is on the order of one minute, suggesting that CEE may hydrolyze too quickly to reach muscle cells in its ester form."
http://www.ncbi.nlm.nih.gov/pubmed/19524547
