Differentiation of Natural and Synthetic Phenylalanine and Tyrosine through Natural Abundance 2H Nuclear Magnetic Resonance
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- 作者：Elisabetta Brenna ; Giovanni Fronza ; Claudio Fuganti ; and Matteo Pinciroli
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2003
- 出版时间：August 13, 2003
- 年：2003
- 卷：51
- 期：17
- 页码：4866 - 4872
- 全文大小：96K
- 年卷期：v.51,no.17(August 13, 2003)
- ISSN：1520-5118
文摘
The natural abundance deuterium NMR characterization of samples of the amino acids tyrosine (1)and phenylalanine (2), examined as the acetylated methyl esters 4 and 6, has been performed withthe aim to identify by these means the contribution in animals of the hydroxylation of the dietL-phenylalanine (2) to the formation of L-tyrosine (1), a feature previously revealed on the samesamples through the determination of the phenolic 
18O values. The study, which includes also theNMR examination of benzoic acid (5) from 2 and of tyrosol (7) from 1, substantially fails in providingthe required information because the mode of deuterium labeling of tyrosine samples of differentorigins is quite similar but indicates a dramatic difference in the deuterium labeling pattern of the twoamino acids 1 and 2. The most relevant variation is with regard to the deuterium enrichments at theCH2 and CH positions, which are inverted in the two amino acids of natural derivation. Moreover,whereas the diastereotopic benzylic hydrogen atoms of L-tyrosine (1) appear to be equally deuteriumenriched, in L-phenylalanine (2) the (D/H)3R > (D/H)3S. Similarly, benzoic acid (5) shows separatesignals for the aromatic deuterium nuclei, which are quite indicative of the natural or syntheticderivation. The mode of deuterium labeling of the side chain of 1 and 2 is tentatively correlated to thedifferent origins of the two amino acids, natural from animal sources for L-tyrosine and biotechnologicalprobably from genetically modified microorganisms for L-phenylalanine.Keywords: Tyrosine; phenylalanine; tyrosol; animal vegetal origin; aspartame; natural abundancedeuterium NMR
18O values. The study, which includes also theNMR examination of benzoic acid (5) from 2 and of tyrosol (7) from 1, substantially fails in providingthe required information because the mode of deuterium labeling of tyrosine samples of differentorigins is quite similar but indicates a dramatic difference in the deuterium labeling pattern of the twoamino acids 1 and 2. The most relevant variation is with regard to the deuterium enrichments at theCH2 and CH positions, which are inverted in the two amino acids of natural derivation. Moreover,whereas the diastereotopic benzylic hydrogen atoms of L-tyrosine (1) appear to be equally deuteriumenriched, in L-phenylalanine (2) the (D/H)3R > (D/H)3S. Similarly, benzoic acid (5) shows separatesignals for the aromatic deuterium nuclei, which are quite indicative of the natural or syntheticderivation. The mode of deuterium labeling of the side chain of 1 and 2 is tentatively correlated to thedifferent origins of the two amino acids, natural from animal sources for L-tyrosine and biotechnologicalprobably from genetically modified microorganisms for L-phenylalanine.Keywords: Tyrosine; phenylalanine; tyrosol; animal vegetal origin; aspartame; natural abundancedeuterium NMR