Erythromycin

Macrolide antibiotics are classified by the size of the macrocyclic lactone ring of aglycone as 14-, 15- or 16-membered ring macrolides. Macrolides are characterized by similar chemical structures, mechanisms of action and resistance, but vary in the different pharmacokinetic parameters, and spectrum of activity. Erythromycin (abbrev: EM), the first 14-membered macrolide, is isolated from a strain of the actinomycete Saccharopolyspora erythraea. EM has activity against a wide range of Gram-positive bacteria including Streptococcus and Staphylococcus, and limited activity against Gram-negative bacteria. EM inhibits protein synthesis in susceptible organisms by binding to specific nucleotides in 23S rRNA within the 50S subunit of the bacterial ribosome. EM and macrolides also shows gastrointestinal motor stimulating activity as a motilin-agonist, and anti-inflammatory or immunomodulatory activity. EM is easily inactivated by gastric acid. Therefore, a number of more stable macrolides such as azithromycin [A2076] and clarithromycin [C2220] have been chemically synthesized from EM.