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13. A LC-MS/MS validated method for determination of azithromycin in human tears and its application to an ocular pharmacokinetic study

Author

Wu, Feng, Zhao, Xiuli, Ni, Siyang, and Yang, Bo

Abstract

A rapid and sensitive method for the quantitative analysis of azithromycin in human tears by LC-MS/MS was developed and validated. Following extraction from collected Schirmer tear strips by methanol-water (4:1, v/v), the analyte and IS (azithromycin-d3) were separated on a Waters Atlantis™ dC18column (2.1 mm × 30 mm, 3 μm) by gradient elution with 0.1% (v/v) formic acid in methanol-water (1:9) and methanol-acetonitrile (9:1) as the mobile phase. Electrospray ionization in positive ion mode and MRM were used to monitor the ion transitions atm/z749.6 → 591.6 (azithromycin) and 752.4 → 594.4 (azithromycin-d3). The results indicated that the method had excellent sensitivity and specificity. The analyte appeared to have good linearity in the range of 5-1000 ng/ mL. Both the intra-batch and inter-batch precisions (in terms of RSD) were <10%, and the accuracies (in terms of RE) were within ±15%. The lower limit of quantification, matrix effect, extraction recovery, stability and dilution integrity were also evaluated and satisfied the validation criteria. Artificial tears served as the surrogate matrix, and no matrix difference was found when compared with that of real human tears. Finally, this method was successfully applied in an ocular pharmacokinetic study in healthy volunteers following instillation of azithromycin eyedrops.

Published
2020
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15. 19-[(1′S,4′R)-4′-Hydroxy-1′-methoxy-2′-oxopentyl]geldanamycin, a Natural Geldanamycin Analogue from Streptomyces hygroscopicus 17997

Author

Li, Shufen, primary, Ni, Siyang, additional, Wu, Linzhuan, additional, Li, Li, additional, Jiang, Bingya, additional, Wang, Hongyuan, additional, Sun, Guizhi, additional, Gan, Maoluo, additional, Li, Jingyan, additional, He, Weiqing, additional, Lin, Ling, additional, Wang, Yiguang, additional, Bai, Shuoke, additional, and Si, Shuyi, additional

Published
2013
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25. Novel 4,5-Dihydro-thiazinogeldanamycin in a gdmPMutant Strain of Streptomyces hygroscopicus17997

Author

LIN, Ling, NI, SiYang, WU, LinZhuan, WANG, YiGuang, WANG, YuCheng, TAO, PeiZhen, HE, WeiQing, and WANG, XiangJing

Abstract

Novel geldanamycin derivative, 4,5-dihydro-thiazinogeldanamycin (3), was characterized from the gdmPmutant in Streptomyces hygroscopicus17997, besides expected 4,5-dihydro-geldanamycin (2). The presence of this compound would suggest an unknown post-PKS modification in geldanamycin biosynthesis. Compound 3exhibited moderate anti-HSV-1-virus activity and higher water solubility than geldanamycin (1). Cysteine served as a precursor to synthesize 3, whose formation required obligatory enzymatic assistance.

Published
2011
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27. Novel 4,5-dihydro-thiazinogeldanamycin in a gdmP mutant strain of Streptomyces hygroscopicus 17997.

Author

Lin L, Ni S, Wu L, Wang Y, Wang Y, Tao P, He W, and Wang X

Subjects
Protein Engineering, Bacterial Proteins genetics, Bacterial Proteins metabolism, Benzoquinones chemistry, Benzoquinones metabolism, Lactams, Macrocyclic chemistry, Lactams, Macrocyclic metabolism, Mutation, Streptomyces genetics, Streptomyces metabolism, Thiazines chemistry, Thiazines metabolism
Abstract

Novel geldanamycin derivative, 4,5-dihydro-thiazinogeldanamycin (3), was characterized from the gdmP mutant in Streptomyces hygroscopicus 17997, besides expected 4,5-dihydro-geldanamycin (2). The presence of this compound would suggest an unknown post-PKS modification in geldanamycin biosynthesis. Compound 3 exhibited moderate anti-HSV-1-virus activity and higher water solubility than geldanamycin (1). Cysteine served as a precursor to synthesize 3, whose formation required obligatory enzymatic assistance.

Published
2011
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28. [Analysis of geldanamycin analogues in trace amounts by LC-MS/MS].

Author

Ni S, Zhang K, Wang Y, He W, Wang Y, He J, and Wu L

Subjects
Anti-Bacterial Agents chemistry, Benzoquinones analysis, Benzoquinones chemistry, Chromatography, Liquid methods, Lactams, Macrocyclic analysis, Lactams, Macrocyclic chemistry, Tandem Mass Spectrometry methods
Abstract

Ansamycins, such as rifamycin and ansamitocin, usually consist of a group of structural similar components. Geldanamycin, a benzenic ansamycin, has been found to consist of four structural similar components. We analyzed the geldanamycin (GDM) preparation from Streptomyces hygroscopicus 17997 by LC-ESI(+)-MS/MS, and discovered five novel and one known GDM analogues in trace amounts. Based on the ESI(+)-MS/MS spectra of these GDM analogues, and the present understanding of GDM biosynthesis, we proposed the possible chemical structures of these GDM analogues. Three novel GDM analogues, all having the same molecular formula of C29H42N2O10, were GDM biosynthetic derivatives with one of the three C-C double bonds between C2-C3, C4-C5 and C8-C9 in GDM changed to mono-hydroxylated C-C single bond. The other two novel GDM analogues, having the same molecular formula of C28H38N2O8, were 17(or 12, or 4)-desmethoxylgeldanamycin and 4,5-dihydro-10,11-dehydrate-17-desmethyl-17-hydroxylgeldanamycin, respectively. The known GDM analogue, having the molecular formula of C29H42N2O9, was 4, 5-dihydrogeldanamycin, an intermediate in GDM biosynthesis. The discovery of novel GDM analogues provided us new insights in understanding the biosynthetic details of GDM, and clues of obtaining GDM derivatives by gene-disruption and combinatorial biosynthesis.

Published
2009

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