Quinupristin is a semisynthetic streptogramin antibacterial agent derived from pristinamycin and belonging to the type-B streptogramin class. It is a complex pharmaceutical active ingredient that acts primarily on bacterial protein synthesis by binding to the bacterial 50S ribosomal subunit. Its CAS Number is 120138-50-3, molecular formula is C₅₃H₆₇N₉O₁₀S, and molecular weight is 1022.23 g/mol. PubChem and the Merck Index report these chemical characteristics.
Quinupristin is best known as one component of the combination antibiotic quinupristin/dalfopristin. In this combination, quinupristin is the type-B streptogramin component and dalfopristin is the type-A component. The two compounds act at different stages of bacterial protein synthesis and demonstrate synergistic antibacterial activity.
Product Name: Quinupristin
CAS Number: 120138-50-3
Molecular Formula: C₅₃H₆₇N₉O₁₀S
Molecular Weight: 1022.23 g/mol
Chemical Class: Streptogramin antibiotic
Antibacterial Class: Type-B streptogramin
Development Code: RP 57669 / RP-57669
API Form: Quinupristin
Appearance: Powder / solid
Therapeutic Area: Antibacterial / anti-infective
FDA GSRS and IUPHAR identify 120138-50-3 as the CAS number for Quinupristin. IUPHAR also lists RP 57669 and RP-57669 among its synonyms.
Quinupristin has a highly complex molecular structure containing numerous stereocenters and functional groups. Its molecular structure and stereochemistry are therefore important quality attributes during API identification and characterization.
Quinupristin is a semisynthetic derivative of pristinamycin and belongs to the streptogramin family of antibacterial compounds. KEGG classifies it as an antibacterial protein-biosynthesis inhibitor acting at the 50S ribosomal subunit.
The mechanism of quinupristin involves inhibition of the late phase of bacterial protein synthesis. It binds to the bacterial ribosome and interferes with peptide-chain elongation, resulting in inhibition of bacterial protein production.
Quinupristin is generally considered together with dalfopristin in pharmaceutical applications because the combination provides synergistic antibacterial activity. The combination has activity against susceptible gram-positive organisms and has been used particularly in infections involving vancomycin-resistant Enterococcus faecium and certain staphylococcal infections.
Quinupristin is primarily associated with the intravenous antibacterial combination quinupristin/dalfopristin. The combination has been used for treatment of serious infections caused by susceptible gram-positive bacteria.
Quinupristin inhibits bacterial protein synthesis at the ribosomal level. When combined with dalfopristin, the two streptogramins produce a synergistic effect that is greater than the activity of either individual component against susceptible organisms.
The combination has historically been used for infections caused by vancomycin-resistant Enterococcus faecium and susceptible staphylococci. The actual clinical indication depends on the approved pharmaceutical product and applicable regulatory requirements.
For API manufacturing, maintaining chemical identity, stereochemical integrity, chromatographic purity and appropriate biological quality is important because Quinupristin is a structurally complex antibiotic.
Quinupristin requires comprehensive analytical characterization because of its complex molecular structure and multiple stereochemical centers.
Identity testing may include ¹H-NMR, mass spectrometry, chromatographic retention-time comparison and other orthogonal analytical techniques. A commercial certificate of analysis for Quinupristin reports ¹H-NMR identification as compliant and a purity specification of >98%. This value is a commercial analytical specification and should not be represented as a universal pharmacopoeial requirement.
Quality assessment may also include chromatographic evaluation of related substances, water or moisture determination, residual solvents, elemental impurities and microbiological quality where applicable.
Because I could not verify a current universal USP or Ph. Eur. monograph providing numerical limits for each of these tests specifically for Quinupristin, the final release specification should be based on the approved manufacturer specification and applicable regulatory requirements rather than transferring values from another streptogramin or from the quinupristin/dalfopristin finished product.
Quinupristin API manufacturing requires controlled synthesis, purification and analytical characterization due to its structurally complex antibiotic nature. Important manufacturing controls can include qualified raw materials, controlled reaction conditions, purification, drying, chromatographic purity testing and identity confirmation.
Batch-to-batch consistency is particularly important for complex pharmaceutical APIs. Appropriate analytical methods can be used to verify chemical identity, assay or purity, related substances and other critical quality attributes.
Depending on the intended market, API specifications can be established against applicable regulatory requirements and customer-approved quality standards.
Quinupristin should be packaged in suitable protective containers and handled under controlled environmental conditions. Commercial analytical information recommends storage at −20°C for research material, but this should not automatically be presented as a universal pharmaceutical API storage requirement.
For pharmaceutical-grade material, final storage conditions should follow validated stability data and the approved product specification. Protection from excessive moisture, heat, light and contamination can help preserve the quality of the API.
Typical documentation for Quinupristin API may include:
Quinupristin is a structurally complex streptogramin antibacterial API with a defined chemical identity, CAS Number 120138-50-3 and molecular weight of approximately 1022.23 g/mol.
Its role as the type-B component of quinupristin/dalfopristin and its activity at the bacterial 50S ribosomal subunit make it an important specialized antibacterial substance.
Controlled manufacturing, appropriate purification, orthogonal identity testing and chromatographic purity assessment are essential for maintaining consistent Quinupristin API quality.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 0.5% |
| Residue on Ignition | NMT 0.1% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |