• Spiramycin packaged and labeled.

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Spiramycin is a broad-spectrum 16-membered ring macrolide antibiotic composed of a mixture of spiramycin I, II, and III.  Spiramycin was first isolated by PINNERT-SINDICO in 1954 from Streptomyces ambofaciens.  

Spiramycin is a bacterial protein synthesis inhibitor, it works by irreversibly binding to the P-site on the 50s ribosome, preventing peptide bond formation and translocation.  Spiramycin is effective against gram-negative and gram-positive bacteria, as well as some Toxoplasma parasites.

Spiramycin has shown anti-obesity effects.  In a recent study (2016), it was shown that spiramycin inhibits adipogenesis in 3T3-L1 cells and ameliorates obesity and associated metabolic indications in HFD-fed mice.

Synonyms: Rovamycine, Formacidine, Foromacidine, NSC 55926, Kitasamycin

    CAS Number


    Molecular Formula

    Spiramycin I: C43H74N2O14

    Molecular Weight

    Spiramycin I: 843.05

    Mechanism of Action

    Macrolide antibiotics, like Spiramycin, inhibit bacterial growth bacteriostatically by targeting the 50S ribosomal subunit preventing peptide bond formation and translocation during protein synthesis. Resistance to spiramycin is commonly attributed to mutations in 50S rRNA preventing spiramycin binding allowing the cell to synthesize proteins free of error.

    Storage Conditions


    Tariff Code



    Spiramycin is a broad-spectrum antibiotic targeting a wide range of gram-positive and gram-negative bacteria. In addition, spiramycin has demonstrated activity against Toxoplasma parasites.


    Eukaryotic Cell Culture Applications

    Spiramycin has shown various anti-obesity effects in 3T3-L1 preadipocytes and in mice models.  Spiramycin is able to inhibit adipogenesis in 3T3-L1 preadipocytes, and reduce lipid accumulation in-vitro.  Spiramycin is also able to decrease adipogenic gene expression by reducing the expression of adipogenic transcriptional factors like, PPARγ, SREBP1c, and C/EBPα, in preadipocytes.  Spiramycin increases AMPK activity during early adipogensis in 3T3-L1 preadipocytes.  Spiramycin ameliorates HFD-induced obesity and obesity-related parameters in C57BL/6 mice.

    Microbiology Applications

    Spiramycin is commonly used in clinical in vitro microbiological antimicrobial susceptibility tests (panels, discs, and MIC strips) against gram positive and gramnegative microbial isolates. Medical microbiologists use AST results to recommend antibiotic treatment options for infected patients. Representative MIC values include:

    • Staphylococcus spp. 0.031 µg/mL – 0.063 µg/mL
    • For a complete list of spiramycin MIC values, click here.





    White or yellowish powder


    Streptomyces Ambofaciens

    Elemental Analysis

    Spiramycin I: Not less than 80.0%
    Spiramycin II: Not more than 5.0%
    Spiramycin III: Not more than 10.0%
    Sum of Spiramycin I, II, III: Not less than 90.0%


    8.5 - 10.5

    Optical Rotation

    -80.0° to -85.0°


    (On Dried Basis): Not less than 4100 IU/mg

    Loss on Drying

    Not more than 3.5%

    Sulfated Ash

    Not more than 0.1%

    Heavy Metals

    Not more than 20 ppm



    Lovmar, Martin, and Tanel Tenson. "The Mechanism of Action of Macrolides, Lincosamides and Streptogramin B Reveals the Nascent Peptide Exit Path in the Ribosome."Journal of Molecular Microbiology 330.5 (2003): 1005-014.

    PINNERT-SINDICO, S., L. Ninet, and J. PREUD. "HOMME & C." COSAR: A new antibiotic-spiramycin. Antibiot. Annual1955 (1954): 724-727.

    Kim MO, Ryu HW, Choi J-H, Son TH, Oh S-R, Lee H-S, et al. (2016) Anti-Obesity Effects of Spiramycin In Vitro and In Vivo. PLoS ONE 11(7): e0158632. https://doi.org/10.1371/journal.pone.0158632

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