1.Stereochemical differentiation of C-7 hydroxyltaxane isomers by electrospray ionization mass spectrometry.
Ge GB1, Zhang R, Ai CZ, He YQ, Zhang YY, Liu XB, Yang L, Wang ZT, Yang L. Rapid Commun Mass Spectrom. 2009 Feb;23(3):425-32. doi: 10.1002/rcm.3892.
In this study, different electrospray ionization mass spectrometric (ESI-MS) methods were utilized to analyze several pairs of taxane stereoisomers including paclitaxel and 7-epi-paclitaxel. Both ESI-MS and tandem mass spectrometry (MS/MS) techniques provided stereochemically dependent mass spectra in negative-ion mode, and all studied stereoisomers could be easily distinguished based on their characteristic ions or distinct fragmentation patterns. MS/MS experiments for several taxane analogues at various collision energies were performed to elucidate potential dissociation pathways. The gas-phase deprotonation potentials were also calculated to estimate the most thermodynamically favorable deprotonation site using DFT B3LYP/6-31G(d). The results of the theoretical studies agreed well with the fragmentation patterns of paclitaxel and 7-epi-paclitaxel observed from MS/MS experiments. In addition, it was found that liquid chromatography (LC)/ESI-MS was a useful and sensitive technique for assignment of C-7 taxane stereoisomers from realistic samples.
2.Simultaneous determination of main taxoids in Taxus needles extracts by solid-phase extraction-high-performance liquid chromatography with pentafluorophenyl column.
Fu YJ1, Sun R, Zu YG, Li SM, Liu W, Efferth T, Gu CB, Zhang L, Luo H. Biomed Chromatogr. 2009 Jan;23(1):63-70. doi: 10.1002/bmc.1085.
A simple and accurate RP-HPLC method with pentafluorophenyl (PFP) column was developed for the simultaneous determination of six taxoids, i.e. paclitaxel, 10-deacetylbaccatin III (10-DAB III), 7-xylosyl-10-deacetyltaxol (7-xyl-10-DAT), 10-deacetyltaxol (10-DAT), cephalomannine and 7-epi-10-deacetyltaxol (7-epi-10-DAT), in the extracts from the needles of three Taxus species. The mobile phase consisted of acetonitrile (A) and water (B), and the extracts were separated using gradient elution program: 30% A at the first 7 min, and then ramped to 42% A at 8 min, held until 38 min. The developed method was validated with satisfactory precision (RSD < 2.61%), repeatability (RSD < 2.92%) and recovery (95.19-104.47%). The above taxoids in the extracts of Taxus cuspidata, T. chinensis and T. media were analyzed with the developed RP-HPLC method, and the results showed that the contents of different taxoids in three mentioned species were distinct.
3.Influence of MiR-451 on Drug Resistances of Paclitaxel-Resistant Breast Cancer Cell Line.
Gu X1, Li JY1, Guo J1, Li PS1, Zhang WH1. Med Sci Monit. 2015 Oct 30;21:3291-7.
BACKGROUND: This study aimed to investigate the potential influence of microRNA-451 (miR-451) in drug resistances of the Paclitaxel-resistant breast cancer cell line by transfecting miR-451 mimics and miR-451 inhibitors to MCE-7, MCF-7/EPI, and MCF-7/DOC.
4.Characterization of human cytochrome P450 isoforms involved in the metabolism of 7-epi-paclitaxel.
Zhang YY1, Liu Y, Zhang JW, Ge GB, Wang LM, Sun J, Yang L. Xenobiotica. 2009 Apr;39(4):283-92. doi: 10.1080/00498250802714907.
The C-7 chiral centre in paclitaxel is subject to epimerization under physiological conditions, thus making 7-epi-paclitaxel as the principal degradant. This study was designed to characterize the cytochrome P450 (CYP) enzymes involved in 7-epi-paclitaxel metabolism, and to examine possible metabolic interactions that this C-7 epimer may have with paclitaxel. In human liver microsomes, 7-epi-paclitaxel was oxidized to two monohydroxylated metabolites while the metabolic sites occurred at the C-13 side-chain for M-1 and taxane core ring for M-2. A combination of correlation analysis, chemical inhibition studies, assays with recombinant CYPs, and enzyme kinetics indicated that M-1 was generated predominantly by CYP3A4 and M-2 by CYP2C8. Co-incubation of 7-epi-paclitaxel with paclitaxel in human liver microsomes resulted in potent inhibition of 6alpha-hydroxypaclitaxel formation (IC((50)) = 2.1 +/- 0.2 muM), thus decreasing the metabolic elimination of paclitaxel.