title: Determination and stereochemistry of proteinogenic and non-proteinogenic amino acids in Saudi Arabian date fruits.
abstract: 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.
authors.affiliation: Department of Food Science and Nutrition, College of Food Science and Agriculture, King Saud University, P.O. Box 2460, Riyadh, 11451, Kingdom of Saudi Arabia.
authors.forename: Hatem Salama Mohamed
authors.initials: HS
authors.lastname: Ali
authors.forename: Omar Amin
authors.initials: OA
authors.lastname: Alhaj
authors.forename: Abdulrahman Saleh
authors.initials: AS
authors.lastname: Al-Khalifa
authors.forename: Hans
authors.initials: H
authors.lastname: Brückner
mesh_terms: D000596:Amino Acids / Q000032:analysis* / Q000737:chemistry; D005638:Fruit / Q000737:chemistry*; D065749:Phoeniceae / Q000737:chemistry*; D010940:Plant Proteins / Q000032:analysis* / Q000737:chemistry; D012529:Saudi Arabia; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D010940:Plant Proteins