Azithromycin

Azithromycin (CAS No. 83905-01-5) is a 15-membered macrolide antibiotic whose core bioactivity is inhibition of bacterial protein synthesis. Its target is the bacterial 50S ribosomal subunit, where it binds to 23S rRNA, affecting the nascent peptide exit tunnel and blocking the translation process. Its MIC shows resistance peptide dependence; for example, the resistance peptide MLLRV has an MIC>200 μg/mL, and MLLLV has an MIC of 120 μg/mL, while the concentration used for screening resistance peptides is 100 μg/mL (corresponding to 1.5 MIC). Common application concentrations: in vitro TLC analysis has a linear range of 5-30 μg/spot, with a quantitation limit of 2 μg/spot; in forced degradation studies, concentrations such as 150 mg/mL (acid/alkali hydrolysis) and 1 mg/20 μL (purity testing) are used; in animal experiments, the concentration added to culture medium for screening resistance peptides is 100 μg/mL. Clinically it is formulated as oral capsules (250 mg/capsule), and the effective therapeutic concentration needs to be adjusted according to clinical indications. It is easily degraded under acidic conditions, and its main impurity is azaerythromycin A (CAS No. 76801-85-9, Cat. No.: BA1060), which has an Rf value of 0.54 in TLC analysis and can be effectively distinguished from impurities and degradation products. It is suitable for the treatment of bacterial infections.

References:

[1] Khedr A, Sheha M. Quantitative thin-layer chromatographic method of analysis of azithromycin in pure and capsule forms. J Chromatogr Sci. 2003 Jan;41(1):10-6. doi: 10.1093/chromsci/41.1.10. PMID: 12597590.

[2] Vimberg V, Xiong L, Bailey M, Tenson T, Mankin A. Peptide-mediated macrolide resistance reveals possible specific interactions in the nascent peptide exit tunnel. Mol Microbiol. 2004 Oct;54(2):376-85. doi: 10.1111/j.1365-2958.2004.04290.x. PMID: 15469510.