АНГИДРОЭРИТРОМИЦИН А

Substance identification

Anhydroerythromycin A is a product of intramolecular dehydration of the antibiotic erythromycin A, a known impurity of erythromycin D. CAS number 23893-13-2, formula C37H65NO12, UNII 2BR5PL6H39. Synonyms: 6,9,12-anhydroerythromycin A; 9-deoxy-6,12-dideoxy-6,9-12-diepoxy-erythromycin; anhydroerythromycin; BRL 46355ER; EM 202; erythromycin anhydride, impurity D; erythromycin anhydride.

Physico-chemical characteristics

• Molecular Weight: 715.916
• Exact mass: 715.45067651 g/mol
• PSA Specs: 154.84
• XLogP3: 2.9886
• Density: 1.21±0.1 g/cm3 (predicted)
• Melting point: 125–127 °C
• Boiling point: 787.2 °C at 760 mm Hg. Art.
• Flash point: 429.9 °C
• Refractive index: 1.54
• Storage conditions: −20 °C
• Steam pressure: 1.23 × 10⁻²⁸ mm Hg. Art. at 25 °C

Substance class and formation

Anhydroerythromycin A is a macrolide antibiotic and is a product of acid-catalyzed intramolecular cyclization of erythromycin A: the hydroxyl group at C-6 attacks the ketone at C-9, which leads to the formation of a spiroketal and then an anhydro derivative with loss of activity. It is formed as the main degradation product of erythromycin during storage in an acidic environment or gastric juice, therefore it is considered as a marker impurity when monitoring the quality of the erythromycin substance (impurity D according to the pharmacopoeial nomenclature).

Meaning and Application

It is used as an analytical reference standard for pharmacopoeial control of the quality and stability of erythromycin and its dosage forms by HPLC methods - it allows for quantitative determination of the content of this related impurity in finished preparations. The intrinsic antibacterial activity of anhydroerythromycin A is significantly reduced compared to the original erythromycin.

Erythromycin as the initial antibiotic

Erythromycin A, a macrolide antibiotic produced by the actinomycete Saccharopolyspora erythraea, binds to the 50S subunit of the bacterial ribosome and blocks the translocation of the growing polypeptide chain, suppressing protein synthesis in sensitive bacteria. It is used for infections of the respiratory tract, skin and soft tissues, as an alternative to penicillins for allergies to them. The acid instability of erythromycin A in the stomach, leading to the formation of anhydroerythromycin A and other degradation products with reduced activity, is one of the reasons for the development of more acid-resistant dosage forms and derivatives (erythromycin ethyl succinate, erythromycin stearate, clarithromycin).

Safety Information

WGK Germany: 3.

Storage

Store at a temperature of −20 °C in an airtight container, protected from moisture and light - the compound is an unstable degradation product of macrolide antibiotics; further storage outside the cold chain accelerates the accumulation of secondary degradation products.