Oxolinic Acid is a synthetic quinolone antibacterial compound identified by CAS No. 14698-29-4 and molecular formula C₁₃H₁₁NO₅. Its molecular weight is 261.23 g/mol. Pharmacopoeial references identify Oxolinic Acid as 5-ethyl-8-oxo-5,8-dihydro-1,3-dioxolo[4,5-g]quinoline-7-carboxylic acid. It is classified as an antibacterial quinolone and has been used primarily in veterinary pharmaceutical applications.
Oxolinic Acid is structurally related to the early quinolone antibacterial class. Its antimicrobial activity is associated with inhibition of bacterial DNA replication through interference with bacterial DNA gyrase and related topoisomerase enzymes. By disrupting essential DNA-processing functions, quinolone compounds can inhibit bacterial growth and replication. Oxolinic Acid has therefore been investigated and used for susceptible bacterial infections, particularly in veterinary medicine.
The API has the molecular formula C₁₃H₁₁NO₅ and molecular weight 261.23 g/mol. PubChem identifies its CAS number as 14698-29-4, EC number 238-750-8, FDA GSRS UNII L0A22B22FT, ChEBI CHEBI:138856, ChEMBL CHEMBL416755, and DrugBank DB13627.
The IUPAC name is 5-ethyl-8-oxo-[1,3]dioxolo[4,5-g]quinoline-7-carboxylic acid. The compound contains a quinolone nucleus with a fused dioxole ring and carboxylic acid functionality. PubChem reports an exact mass of 261.06372245 Da, topological polar surface area of 76.1 Ų, six hydrogen-bond acceptors, one hydrogen-bond donor and two rotatable bonds.
Oxolinic Acid is covered by Ph. Eur. monograph 1353, reproduced in the BP 2025 edition incorporating the Ph. Eur. 11.6 update. The pharmacopoeial monograph specifies a content of 98.0% to 102.0% calculated on the dried substance. The official-style assay is performed by potentiometric titration using tetrabutylammonium hydroxide rather than an HPLC assay.
The pharmacopoeial material is described as an almost white or pale yellow crystalline powder. It is practically insoluble in water and ethanol 96%, very slightly soluble in methylene chloride, and dissolves in dilute alkali hydroxide solutions.
For identification, the pharmacopoeial procedure includes UV-visible spectrophotometry, infrared absorption spectrophotometry and thin-layer chromatography. The UV procedure specifies absorption maxima at 260 nm, 322 nm and 336 nm, with an A260/A336 ratio of 4.9–5.2. Infrared identification is performed against Oxolinic Acid CRS.
Quality control is particularly important for pharmaceutical-grade Oxolinic Acid API. The Ph. Eur. monograph specifies TLC-based limits for related substances. Oxolinic Acid impurity B is limited to 0.2%, while impurities A and C are each limited to 0.4% under the prescribed TLC comparison procedure. The monograph also specifies loss on drying NMT 0.5%, determined at 105°C.
The pharmacopoeial requirement for sulfated ash is NMT 0.1%. Oxolinic Acid should be stored protected from light to support appropriate material stability and quality maintenance.
Oxolinic Acid has historically been associated with antibacterial applications, particularly veterinary pharmaceutical formulations. It belongs to the quinolone antibacterial class and has been investigated against susceptible Gram-negative and other bacterial organisms. Its physicochemical properties and antibacterial mechanism make it relevant as a pharmaceutical raw material for appropriate regulated applications.
The compound is also available as an analytical reference material for veterinary-drug and residue-analysis applications. Commercial analytical references commonly specify high chromatographic purity, while pharmaceutical manufacturers should distinguish such analytical-grade specifications from pharmacopoeial API requirements. For example, FUJIFILM Wako lists Oxolinic Acid analytical standards with 98.0% or greater assay, depending on the specific standard, while other laboratory suppliers publish their own technical specifications.
A reliable Oxolinic Acid API manufacturing program should include controlled raw materials, validated synthesis and purification processes, appropriate in-process controls, analytical testing and documented batch release. Identity testing can incorporate FTIR, UV-visible spectroscopy and chromatographic comparison, while assay and related-substance testing should follow the applicable pharmacopoeial or approved specification.
For customers sourcing Oxolinic Acid for pharmaceutical or veterinary manufacturing, important documentation can include a Certificate of Analysis, specification sheet, batch information, analytical test results, safety documentation and appropriate regulatory documentation. The exact release specification should always correspond to the intended regulatory market and approved product specification.
Pharmaceutical-grade Oxolinic Acid should provide consistent chemical identity, assay, impurity control, physical appearance and moisture characteristics. The BP/Ph. Eur. monograph provides a useful benchmark, including 98.0–102.0% content on the dried substance, loss on drying NMT 0.5%, sulfated ash NMT 0.1%, and defined limits for specified impurities.
For API procurement and formulation development, maintaining traceability and batch-to-batch consistency is essential. Oxolinic Acid should therefore be evaluated against the applicable pharmacopoeial standard and customer-specific requirements before use in pharmaceutical manufacturing.
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| 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% at 105°C |
| Residue on Ignition | NMT 0.1% |
| Water Content | NMT 0.5% |
| Melting Point | About 313°C, decomposes |