Amino Acids

, Volume 46, Issue 9, pp 2241–2257 | Cite as

Determination and stereochemistry of proteinogenic and non-proteinogenic amino acids in Saudi Arabian date fruits

  • Hatem Salama Mohamed Ali
  • Omar Amin Alhaj
  • Abdulrahman Saleh Al-Khalifa
  • Hans BrücknerEmail author
Original Article


Whereas an abundance of literature is available on the occurrence of common proteinogenic amino acids (AAs) in edible fruits of the date palm (Phoenix dactylifera L.), recent reports on non-proteinogenic (non-coded) AAs and amino components are scarce. With emphasis on these components we have analyzed total hydrolysates of twelve cultivars of date fruits using automated ion-exchange chromatography, HPLC employing a fluorescent aminoquinolyl label, and GC–MS of total hydrolysates using the chiral stationary phases Chirasil®-L-Val and Lipodex® E. Besides common proteinogenic AAs, relatively large amounts of the following non-proteinogenic amino acids were detected: (2S,5R)-5-hydroxypipecolic acid (1.4–4.0 g/kg dry matter, DM), 1-aminocyclopropane-1-carboxylic acid (1.3–2.6 g/kg DM), γ-amino-n-butyric acid (0.5–1.2 g/kg DM), (2S,4R)-4-hydroxyproline (130–230 mg/kg DM), l-pipecolic acid (40–140 mg/kg DM), and 2-aminoethanol (40–160 mg/kg DM) as well as low or trace amounts (<70 mg/kg DM) of l-ornithine, 5-hydroxylysine, β-alanine, and in some samples (<20 mg/kg DM) of (S)-β-aminoisobutyric acid and (<10 mg/kg DM) l-allo-isoleucine. In one date fruit, traces of α-aminoadipic acid could be determined. Enantiomeric analysis of 6 M DCl/D2O hydrolysates of AAs using chiral capillary gas chromatography–mass spectrometry revealed the presence of very low amounts of d-Ala, d-Asp, d-Glu, d-Ser and d-Phe (1.2–0.4 %, relative to the corresponding l-enantiomers), besides traces (0.2–1 %) of other d-AAs. The possible relevance of non-proteinogenic amino acids in date fruits is briefly addressed.


Phoenix dactylifera (2S,5R)-5-hydroxypipecolic acid 1-aminocyclopropane-1-carboxylic acid Non-coded amino acids d-amino acids Plant amino acids Ion-exchange chromatography GC–MS Nutritional relevance 



Gas chromatography mass spectrometry


Molecular mass (weight)


High performance liquid chromatography


Selected ion monitoring


6-Aminoquinoyl-carbamyl-N-hydroxysuccinimidyl carbamate




Isobaric tag for relative and absolute quantitation




Deuterium chloride in deuterium oxide


Trifluoroacetic acid anhydride








Dimethylpolysiloxane functionalized with l-Val-tert.butylamide

Lipodex® E


Common proteinogenic amino acids (AAs) are abbreviated according to three-letter code and are of the l-configuration; non-proteinogenic amino acids are abbreviated as follows:

α-aminoadipic acid

α-Aaa or a-AAA

β-Ala or b-Ala


Aba or a-AB

α-Amino-n-butyric acid

β-Aba or β-Aib

β-Aminoisobutyric acid


1-Aminocyclopropane-1-carboxylic acid








γ-Amino-n-butyric acid

Hyl or Hy-Lys



(2S,4R)-4-hydroxyproline (trans-4-hydroxy-l-proline)


Norleucine (internal standard)




Pipecolic acid


(2S,5R)-5-hydroxypipecolic acid (trans-5-hydroxypipecolic acid)

Amino compounds being part of reference standards but not detected in hydrolysates:



















This project was supported by NSTIP strategic technologies program number 11-AGR 1600-2 of the Kingdom of Saudi Arabia. HB acknowledges his position as a Visiting Professor and Scientific Consultant at KSU. Special thanks are addressed to Katja Dettmer, University of Regensburg, and Małgorzata Jaworska, National Medicines Institute, Warsaw, Jürgen Gerhardt, C.A.T. Tübingen, and Frank Gutjahr, Chromatographie Balingen, for valuable discussions and assistance in parts of the work, in particular disproving or confirming the presence of tentatively assigned amino compounds in selected date samples.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© Springer-Verlag Wien 2014

Authors and Affiliations

  • Hatem Salama Mohamed Ali
    • 1
  • Omar Amin Alhaj
    • 1
  • Abdulrahman Saleh Al-Khalifa
    • 1
  • Hans Brückner
    • 2
    • 3
    Email author
  1. 1.Department of Food Science and Nutrition, College of Food Science and AgricultureKing Saud UniversityRiyadhKingdom of Saudi Arabia
  2. 2.Department of Food Sciences, Research Center for BioSystems Land Use and Nutrition (IFZ), Institute of Nutritional ScienceJustus-Liebig-University of GiessenGiessenGermany
  3. 3.King Saud UniversityRiyadhKingdom of Saudi Arabia

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