Para-Aminosalicylic Acid API, also known as 4-Aminosalicylic Acid, p-Aminosalicylic Acid, or PAS, is an established pharmaceutical active ingredient belonging to the aminobenzoic acid class. It is an antitubercular agent and has historically been used as part of multidrug treatment regimens for tuberculosis. The compound is chemically identified as 4-amino-2-hydroxybenzoic acid, with the molecular formula C7H7NO3, molecular weight 153.14 g/mol, and CAS Number 65-49-6.
Para-Aminosalicylic Acid API is supplied as a pharmaceutical-grade active ingredient for formulation and pharmaceutical manufacturing applications. The substance is a small organic molecule containing amino, hydroxyl and carboxylic acid functional groups. Its physicochemical characteristics, purity and impurity profile are important considerations for API quality control.
PubChem identifies 4-Aminosalicylic Acid with CAS 65-49-6, molecular formula C7H7NO3, and molecular weight 153.14 g/mol.
Para-Aminosalicylic Acid has an established role in antitubercular therapy. It has been used particularly in tuberculosis treatment regimens where multidrug therapy is required.
Applications include:
The compound is recognized as an antitubercular agent and is associated with treatment of tuberculosis.
The current USP 2025 monograph identifies Aminosalicylic Acid as containing 98.5%–100.5% of C7H7NO3, calculated on the anhydrous basis. The USP assay is performed using liquid chromatography with UV detection at 254 nm.
Important USP quality parameters include:
The USP identification procedure includes spectrophotometric maxima at 265 ± 2 nm and 299 ± 2 nm, with an absorbance ratio of 1.50–1.56.
Impurity control is an important part of Para-Aminosalicylic Acid API quality evaluation. The USP monograph specifically controls m-aminophenol, an important process-related impurity.
The USP limit for m-aminophenol is NMT 0.25%. Chloride is controlled at NMT 0.042%, while residue on ignition is limited to NMT 0.2%.
These parameters provide useful controls for pharmaceutical-grade API quality and help establish consistency between manufacturing batches.
Para-Aminosalicylic Acid is reported as a white or nearly white solid. PubChem records experimental physical descriptions including white or nearly white solid and crystalline forms.
The commonly reported melting point is approximately 150–151°C, although literature has reported variation and decomposition behavior. PubChem lists 150.5°C, while other references report approximately 150–151°C.
The compound has limited water solubility compared with its alkaline salts. Historical pharmaceutical references report approximately 1 g in 600 mL water and 1 g in approximately 21 mL alcohol.
Quality testing of Para-Aminosalicylic Acid API can include:
The USP assay method uses LC with a 254 nm UV detector, an L1 column and a specified system-suitability requirement of NLT 1.7 resolution between aminosalicylic acid and acetaminophen.
USP specifies preservation of Aminosalicylic Acid in tight, light-resistant containers at a temperature not exceeding 30°C.
Recommended handling considerations include:
Para-Aminosalicylic Acid Bulk API is intended for pharmaceutical manufacturing and formulation development. Buyers and pharmaceutical manufacturers should verify the exact API identity, CAS Number, assay basis, water specification, impurity limits and applicable pharmacopoeial requirements before release or use.
For a USP-oriented specification, the principal numerical controls include 98.5–100.5% assay, NMT 0.5% water, NMT 0.2% residue on ignition, NMT 0.042% chloride, and NMT 0.25% m-aminophenol.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.5–100.5% (anhydrous basis) |
| Residue on Ignition | NMT 0.2% |
| pH (1% Solution) | 3.0–3.7 |
| Water Content | NMT 0.5% |
| Melting Point | 150.5°C (reported physical property; not a USP release limit) |