4-Aminosalicylic acid

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Cat Number

API65496

CAS Number

65-49-6

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CAS Number

65-49-6

EINECS

200-613-5

Storage

Store at room temperature

Synonyms

4-Amino-2-hydroxybenzoic acid; Aminosalicylic acid; P-AMINOSALICYLIC ACID; Paramycin; Parasal

Molecular Formula

C7H7NO3

Molecular Weight

153.14

Smiles

C1=CC(=C(C=C1N)O)C(=O)O

Appearance

White to off-white crystalline powder

Melting Point

150-151℃

Boiling Point

380.8±32.0℃ at 760 mmHg

Relative Density

1.545

General Description

4-Aminosalicylic acid (PAS) is a bacteriostatic antituberculosis agent structurally related to para-aminobenzoic acid (PABA). It is typically used in combination therapy for multidrug-resistant tuberculosis (MDR-TB).

Mechanism of Action

PAS inhibits folate synthesis in Mycobacterium tuberculosis by competing with PABA for the enzyme dihydropteroate synthase, similar to sulfonamides. This blocks the formation of dihydrofolic acid, depriving the bacteria of essential purine and thymidine precursors. Unlike sulfonamides, PAS is selective for mycobacteria and is not significantly active against other bacteria. Resistance emerges rapidly when used alone, necessitating combination regimens.

Application

PAS is indicated for the treatment of active tuberculosis caused by susceptible strains when first-line agents (isoniazid, rifampin) cannot be used or have failed.

A microporous hydrogel was synthesized by conjugating sodium alginate with 4‑aminosalicylic acid (4‑ASA), introducing additional carboxyl and hydroxyl groups that provide lubrication and stress‑triggered sol‑gel transition. The hydrogel was non‑toxic to human dermal fibroblasts. Drug release showed 49.6% in 8 hours and 97.5% in 72 hours. Rheological evaluation confirmed significant gelling properties and thixotropic behavior (thixotropic area 26.23%). The modified hydrogel offers potential as a biomimetic synovial fluid for joint injuries and arthritis, combining thixotropy, non‑toxicity, and drug release capabilities for viscosupplementation.

Fig. 1 Scanning electron micrographs of hydrogels. (Chejara DR, et al., 2017)

References

Chejara DR, et al. Synthesis and Evaluation of a Sodium Alginate-4-Aminosalicylic Acid Based Microporous Hydrogel for Potential Viscosupplementation for Joint Injuries and Arthritis-Induced Conditions. Mar Drugs. 2017;15(8):257.

Nano‑cocrystals of 4‑aminosalicylic acid and sulfamethazine (form I, high crystallinity) were prepared by high‑pressure homogenization (HPH) and high‑power ultrasound. HPH produced needle‑like nano‑sized cocrystals (smaller size, narrow distribution) whereas ultrasound gave micro‑sized particles with different morphology. Both methods enhanced dissolution of sulfamethazine, but HPH yielded the greatest improvement. The study demonstrates that HPH is superior for producing nano‑cocrystals with better dissolution properties.

Fig. 2 Differential scanning calorimetry (DSC) thermograms of the cocrystals. (Salem A, et al., 2021)

References

Salem A, et al. Synthesis and Characterization of Nano-Sized 4-Aminosalicylic Acid-Sulfamethazine Cocrystals. Pharmaceutics. 2021;13(2):277.

Does 4-Aminosalicylic acid require protection from light and air?

Yes, it is highly sensitive to light and oxygen, leading to discoloration (darkening) and formation of m-aminophenol. Store in light-resistant, airtight containers.

What is the recommended storage temperature for 4-Aminosalicylic acid?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which accelerates decarboxylation and oxidative degradation.

Is 4-Aminosalicylic acid stable in solution for gastrointestinal use?

Aqueous solutions degrade rapidly. For oral suspensions, we recommend extemporaneous preparation and immediate use. We provide stability data for various buffers.

How is the impurity m-aminophenol monitored during stability?

This primary decarboxylation and degradation product is specifically quantified using a validated HPLC method, ensuring it remains within pharmacopoeial limits.