Tiejie Wang

Use of various β‐cyclodextrin derivatives as chiral selectors for the enantiomeric separation of ofloxacin and its five related substances by capillary electrophoresis

A capillary electrophoretic method for the enantioseparation of ofloxacin and its five related substances (potential impurities, indicated as impurities B-F) was developed using β-cyclodextrin derivatives as chiral selectors. To our knowledge, there are no previous studies about using capillary electrophoresis for the separation of impurities B-D. Six β-cyclodextrin derivatives including cationic (piperidine- and cyclohexylamine-), neutral (dimethyl- and hydroxypropyl-), and anionic (carboxymethyl- and sulfated-) β-cyclodextrin derivatives were tested and operational parameters such as buffer pH and concentration of β-cyclodextrin derivatives were investigated. The best resolutions were all obtained with anionic β-cyclodextrin derivatives: ofloxacin, impurities C-F could be best resolved with carboxymethyl-β-cyclodextrin at satisfactory resolutions of 8.27, 9.98, 5.92, 8.49 and 6.78, respectively, while for impurity B, a particularly impressive resolution value, up to 21.38, was observed using sulfated-β-cyclodextrin. The enhancement of enantioseparation observed for the tested analytes using anionic β-cyclodextrin derivatives might be due to some favorable interaction between selectors and analytes. Given the fact that the selection of chiral selector depends on the structures of analytes, with the help of structural similarities and differences of the analytes, the structure-separation relationship was further discussed.

Novel HPLC Method to Evaluate the Quality and Identify the Origins of Longjing Green Tea

A novel model of evaluating the quality and identifying the origins of Longjing green tea was established for the first time in this study. The analysis procedures in the model included the structure speculation of the major compounds and the identification of the bioactive components, the establishment of the fingerprint, the multiple analysis of the fingerprint, and the quantitative determination of the bioactive components. All the analysis procedures were conducted on an HPLC coupled with diode array detection (DAD) and an ion-trap coupled with a time-of-flight mass spectrometry (IT-TOF-MS). In this study, 13 batches of Longjing green tea from five traditional production sites and a new production site in Hangzhou, China were selected to establish the model. The result showed that using the model, the difference between Longjing green tea from the traditional and the new production sites was revealed successfully. It indicated that the model could be successfully applied to evaluate the quality and identify the origin of unknown Longjing green tea.

Identification and dynamic analysis of the purine alkaloids in rat plasma after oral administration of green tea by liquid chromatography hybrid ion trap time-of-flight mass spectrometry

A liquid chromatography hybrid ion trap time-of-flight mass spectrometric (LC-IT-TOF-MS) method was developed and validated for identification and simultaneous determination of the potential bioactive components from green tea in rat plasma. The plasma samples were extracted by liquid-liquid extraction with ethyl acetate and separated on Shim-pack XR-ODS II column by a gradient elution within a runtime of 8.0 min. The mobile phase consisted of A (0.1% formic acid in acetonitrile) and B (0.1% formic acid in water) at a flow rate of 0.4 ml/min. Two prototype components and one metabolite were successfully identified as caffeine, theobromine and theophylline according to their retention times, accurate molecule weight, and major fragment ions. Then they were determined with the addition of two internal standards, hypoxanthine and paracetamol. The linear range was 10-10,000 ng/ml for caffeine, 2.0-2000 ng/ml for theobromine and 1.0-1000 ng/ml for theophylline, respectively. Intra-day and inter-day precision were within 6.0% and 10.9%, and accuracy was less than 4.8% and 6.5%, respectively. The validated method was successfully applied to investigate the dynamic change rules of caffeine, theobromine and theophylline in rat plasma after oral administration of caffeine, theobromine and green tea extract. The comparative analysis of the pharmacokinetic parameters indicated that there were obvious differences between green tea extract administration and single substances administration.

Identification of Salvia species using HPLC combined with chemical pattern recognition analysis

Salvia miltiorrhiza, also known as Danshen, is a widely used traditional Chinese medicine for the treatment of cardiovascular diseases and hematological abnormalities. The root and rhizome of Salvia przewalskii and Salvia yunnanensis have been found as substitutes for Salvia miltiorrhiza in the market. In this study, the chemical information of 14 major compounds in Salvia miltiorrhiza and its substitutes were determined using a high-performance liquid chromatography method. Stepwise discriminant analysis was adopted to select the characteristic variables. Partial least squares discriminant and hierarchical cluster analysis were performed to classify Salvia miltiorrhiza and its substitutes. The results showed that all of the samples were correctly classified both in partial least squares discriminant analysis and hierarchical cluster analysis based on the four compounds (caffeic acid, rosmarinic acid, salvianolic acid B, and salvianolic acid A). This method can not only distinguish Salvia miltiorrhiza and its substitutes, but also classify Salvia przewalskii and Salvia yunnanensis. The method can be applied for the quality assessment of Salvia miltiorrhiza and identification of unknown samples.