Development and validation of a high performance liquid chromatography-tandem mass spectrometry method for the absolute analysis of 17 α D-amino acids in cooked meals

Abstract

In the nutrition field, there is a lack of understanding about the impact that dietary chiral composition may have on health, especially regarding cooked meals. Chiral amino acids (AAs) are naturally present in food and their proportion may vary quite a lot. Besides, the D-amino acids (D-AAs) are present in very low concentration compared to L-AAs, so very sensitive methods are required for their accurate quantitation. Moreover, some of them have been described as indicators of quality and different food processes. In this research, we propose a robust method for the absolute quantitation and enantiomeric ratio of 17 D-AAs in cooked meals. The AAs were extracted from 1 g of the homogenised meal with methanol, derivatised with (S)-N-(4-nitrophenoxycarbonyl) phenylalanine methoxyethyl ester ((S)-NIFE) and analysed by RP-LC-MS/MS. The separation was carried out with an Acquity BEH C18 (100 mm x 2.1 mm, 1.7 µm) column at 70º C, with 10 mmol/L ammonium bicarbonate in water as eluent A and acetonitrile as eluent B at a 0.3 mL/min flow rate in gradient elution. The MS operated in positive electrospray ionisation method in multiple reaction monitoring (MRM) mode. Isotopically labelled AAs were used as internal standards for the quantitation. The method was validated for 17 D-AAs in the cooked food samples in terms of specificity, linearity, precision, accuracy, matrix effect and stability. LLOQ are 2.0 ng/mL for most of them. Additionally, linearity was also studied for L-AAs. After optimization and validation, the method was applied to real breakfast, lunch and dinner samples of cooked meals (n=18) that were part of a diet with a very high concordance with WHO dietary guidelines. Level of concentration of major and minor D-AAs have been described per total daily intake and within each of the three main meals. This method can be used for quality control purposes as well as to investigate the role of chiral composition in food and clinical outcomes.

Stereochemistry of aminoacylated cardiolipins and phosphatidylglycerols from bacteria

“…Identification of all (S)-NIFE AA derivatives was performed using precursor and product ions. Based on analyses already published [41][42][43], the ion at m/z 120.0809 was chosen as the product ion. A probable structure is shown in Figure S4, see also the already published paper [43].…”

D-Amino Acids in Kidney Diseases

“…However, recent advancements in amino acid analysis technology now enable the high-precision detection of D-form amino acids. 1 The pharmacokinetics and functions of small amounts (around μ M) of D-amino acids in living organisms are now known. This extremely small amount of D-amino acid reportedly has various physiologic activities.…”