ABSTRACT
We utilized a multi-step derivatization gas chromatography-mass spectrometry method for the determination of common amino acid enantiomers, combined with deuterated hydrochloric acid hydrolysis, to identify nine trace D-amino acids in thymalfasin. We optimized the conditions for multi-step derivatization, the volume of reagent for redissolving samples, and the conditions for chromatography and mass spectrometry with isopropanol and trifluoroacetic anhydride as derivatization reagents, and validated the procedure, including sensitivity, linear range, precision, accuracy and recovery. Sixteen pairs of D/L-amino acids and glycine derivatives were separated within 29 min, with the limit of quantification as low as 0.09-2.79 μmol·L-1. Nine amino acid derivatives of thymalfasin showed a good linear relationship within the concentration range examined (r2>0.992 3). The precision results showed that RSD values were less than 10.90%. Accuracy test results of a reference substance ranged from 76.69% to 128.18%. Average recoveries of spiked samples ranged from 70.41% to 125.39%. For the nine D-amino acids assayed, D-Asp and D-Glu content in six batches of thymalfasin were highest, ranging 0.41%-0.49% and 0.25%-0.33%, respectively, with others less than 0.25%. The method is sensitive, efficient and reliable, available for seventeen common amino acids and their enantiomers, and works well with simultaneous determination of nine trace D-amino acids in thymalfasin, providing a reference for the comprehensive control of racemic peptide impurities in this synthetic polypeptide drug.
ABSTRACT
OBJECTIVE: To develop an ultra-high performance liquid chromatography coupled with quadrupole tandem time-of-flight mass spectrometry method for simultaneous determination of nine trace D-amino acids in thymalfasin, combined with deuterated acid hydrolysis and precolumn-derivatization. METHODS: The sample was hydrolyzed by deuterated acid, followed by precolumn-derivatization with Nα-(2, 4-dinitro-5-fluorophenyl)-L-alaninamide (FDAA). The analysis was then performed on an ACCQ-TAGTM ULTRA C18 column (2.1 mm×100 mm, 1.7 μm), with mobile phase comprising water containing 0.1% formic acid-acetonitrile gradiently eluted at a flow rate of 0.3 mL•min-1. Nine D-amino acids in thymalfasin were correctly quantified using standard curves by Xevo G2-S Q-TOF coupled with electrospray ion source in positive ion mode. RESULTS: The standard curves of the nine D-amino acids derivatives had good linearity in the ranges of the tested concentrations (r>0.991 2). The limits of quantitation of all D-amino acids derivatives were as low as 0.05-0.30 pmol. The precision and recoveries met the requirements of Chinese Pharmacopoeia (2015). The contents of D-amino acids in the samples from five companies were determined to be 25.16-1 322.01 μg•g-1. Among them, D-glutamate, D-aspartate, D-lysine and D-serine had higher contents, which were 1 105.45-1 322.01, 614.15-740.50, 358.06-388.76 and 138.78-291.60 μg•g-1, respectively. CONCLUSION: The method is sensitive, efficient and reliable, working well for simultaneous determination of nine trace D-amino acids in thymalfasin, which provides a reference for the comprehensive control of racemic peptide impurities in this synthetic polypeptide drug.
ABSTRACT
Chiral amino acid analysis is a sensitive, efficient and economical method for controlling racemic peptide impurities, especially for synthetic polypeptide drugs with complex composition of amino acids. Unexpected amino acid enantiomers in racemic peptides can be measured by chiral amino acid analysis coupled with mass spectrometry. The position of amino acid isomerization in the peptide segment can be accurately mapped by mass spectrometry, which lays a solid foundation for screening of racemic peptide impurities and rapid identification or quantification of trace racemic peptide impurities. Combination of the two techniques is vital for quality control of the synthetic polypeptide drugs and for research of polypeptide drugs based on chemical synthesis. The strategies of peptide hydrolysis have been summarized in this review. The latest chiral amino acid analysis based on mass spectrometry is briefly reviewed. Based on our knowledge, we have pointed to the direction of research and control of racemic peptide impurities in synthetic polypeptide drugs.
ABSTRACT
<p><b>AIM</b>To study the chemical constituents of Viscum liquidambaricolum Hayata.</p><p><b>METHODS</b>Various chromatographic techniques were used to separate and purify the compounds. Their spectral data (MS,IR,NMR) were measured for structure identification.</p><p><b>RESULTS</b>Five compounds were isolated from Viscum liquidambaricolum and their structures were identified as trans-cinnamic acid (I), oleanolic acid (II), chrysin (III), eriodictyol (IV) and liquidamboside (V).</p><p><b>CONCLUSION</b>Liquidamboside (V) is a new compound, the known compounds I - IV were isolated from this plant for the first time, I, III, IV were isolated from Loranthaceae for the first time.</p>