Towards the chiral metabolomics: Liquid chromatography-mass spectrometry based DL-amino acid analysis after labeling with a new chiral reagent, (S)-2,5-dioxopyrrolidin-1-yl-1-(4,6-dimethoxy-1,3,5-triazin-2-yl)pyrrolidine-2-carboxylate, and the application to saliva of healthy volunteers.
A novel triazine-type chiral derivatization reagent, i.e., (S)-2,5-dioxopyrrolidin-1-yl-1-(4,6-dimethoxy-1,3,5-triazin-2-yl) pyrrolidine-2-carboxylate (DMT-(S)-Pro-OSu), was developed for the highly sensitive and selective detection of chiral amines and amino acids by UPLC-MS/MS analysis. The enantiomers of amino acids were easily labeled with the reagents at room temperature within 40 min in an alkaline medium containing triethylamine. The diastereomers derived from proteolytic amino acids, except serine, were well separated under isocratic elution conditions by reversed-phase chromatography using an ODS column (Rs=1.2-9.0). DL-Serine was separated by use of an ADME column which has relatively higher polar surface than the conventional ODS column. The characteristic product ions, i.e., m/z 195.3 and m/z 209.3, were detected from all the diastereomers by the collision-induced dissociation of the protonated molecule. A highly sensitive detection on the amol-fmol level was obtained from the selected reaction monitoring (SRM) chromatogram. The chiral amines (e.g., adrenaline and noradrenaline) labeled with DMT-(S)-Pro-OSu were also well separated and sensitively detected by the present procedure. The method using DMT-(S)-Pro-OSu was used for the determination of DL-amino acids in the human saliva from healthy volunteers. Various L-amino acids were identified in the saliva. Furthermore, D-alanine (D-Ala) and D-proline (D-Pro) were also detected in relatively high concentrations (>5%). The ratio was higher in male saliva than in female saliva. However, the difference in the ratio of D-Ala for one day was not very high and the effect of foods and beverage seemed to be negligible. Based on the results using L-Ala-d3, the D-Ala in saliva seemed to be produced due to the racemization with some enzymes such as racemase. The racemization reaction was reversible, i.e., D-Ala-d3 was also racemized to L-Ala-d3 in saliva. Thus, care should be taken during the analysis of DL-amino acids in saliva. The present method using DMT-(S)-Pro-OSu may be applicable for the determination of chiral amine metabolomics, because the resulting derivatives produce the same product ions without relation to the compounds and show highly sensitive detection in the SRM mode of MS/MS. Consequently, DMT-(S)-Pro-OSu seems to be a useful chiral derivatization reagent for the determination of amines and amino acids in biological samples.
Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Toshiki
T
Mochizuki
Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Takahiro
T
Takayama
Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Kenichiro
K
Todoroki
Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Koichi
K
Inoue
Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
Jun Zhe
JZ
Min
Laboratory of Analytical and Bio-Analytical Chemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan. Electronic address: toyooka@u-shizuoka-ken.ac.jp.
Toshimasa
T
Toyo'oka
D000328:Adult; D000596:Amino Acids / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003998:Dicarboxylic Acids / Q000737:chemistry*; D005260:Female; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry; D008297:Male; D055432:Metabolomics / Q000379:methods*; D011759:Pyrrolidines / Q000737:chemistry*; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013237:Stereoisomerism; D053719:Tandem Mass Spectrometry / Q000379:methods*; D055815:Young Adult
D000596:Amino Acids; D003998:Dicarboxylic Acids; D007202:Indicators and Reagents; D011759:Pyrrolidines; C103758:pyrrolidine-2,3-dicarboxylic acid
Amino acids; Chiral derivatization reagent; Chiral metabolomics; Mass spectrometry; Reversed-phase chromatography; Saliva analysis