Enantioseparation of chiral aromatic amino acids by capillary electrophoresis in neutral and charged cyclodextrin selector modes.
Simultaneous enantioseparations of 15 racemic aromatic amino acids and L-mimosine for their chiral discrimination were achieved by neutral selector-modified capillary electrophoresis (CE) and by charged selector-modified CE. Among the diverse cyclodextrins (CDs) examined, hydroxypropyl (HP)-alpha-CD as the neutral selector and highly sulfated (HS)-gamma-CD as the charged selector provided best chiral environments of different enantioselectivities. Fairly good enantiomeric resolutions were achieved with the HP-alpha-CD mode except for racemic 6-hydroxy-3,4-dihydroxyphenylalanine, threo-3,4-dihydroxyphenylserine and homophenylalanine while high-resolution separations of all the enantiomeric pairs were achieved in the HS-gamma-CD mode except that L-mimosine was not detected and a partial resolution (0.6) for threo-3,4-dihydroxyphenylserine enantiomers. Relative migration times to that of internal standard under the respective optimum conditions were characteristic of each enantiomer with good precision (% RSD: 0.7-3.8), thereby enabling to cross-check the chemical identification of aromatic amino acids and also their chiralities. The method linearity was found to be adequate (r> 0.99) for the chiral assay of the aromatic amino acids investigated. When applied to extracts of three plant seeds, nonprotein amino acids such as L-mimosine (42 nug/g) from Mimosa pudica Linné, and L-3,4-dihydroxyphenylalanine (268 nug/g) from Vicia faba were positively detected along with L-tryptophan, L-phenylalanine and L-tyrosine.
La
Sookie
S
College of Pharmacy, Sungkyunkwan University, Suwon, Korea.
Ahn
Sungyeon
S
Kim
Jung-Han
JH
Goto
Junichi
J
Choi
One-Kyun
OK
Kim
Kyoung-Rae
KR
D024322:Amino Acids, Aromatic / Q000737:chemistry* / Q000302:isolation & purification*; D003505:Cyclodextrins; D019075:Electrophoresis, Capillary / Q000379:methods; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007536:Isomerism; D008898:Mimosine / Q000737:chemistry / Q000302:isolation & purification; D015203:Reproducibility of Results; D012639:Seeds / Q000737:chemistry; D013237:Stereoisomerism
D024322:Amino Acids, Aromatic; D003505:Cyclodextrins; D007202:Indicators and Reagents; D008898:Mimosine