Determination of D-amino acids in thymalfasin by GC-MS based on multi-step derivatization / 药学学报

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.

Effective strategies for improving the stability of peptides in vivo / 药学学报

Peptides have been extensively used in the fields of gene/drug delivery and disease targeting therapy. However, natural peptides are sensitive to protease digestion with short circulatory half-lives in vivo. Many studies on structural modifications of peptides have been reported to improve the delivery or therapeutic effect. In this review we focus on the recent literature on peptide stability in accordance with different structural modifications and summarize the methods and influential factors that are involved in the improvement of stability and half-life in vivo. This review will provide the scientific basis and theoretical references for further investigations and applications in vivo.