Para-Aminosalicylic Acid (PASA)

Chemical Structure / Formula of Para-Aminosalicylic Acid (PASA)

  • Formula: C₇H₇NO₃
  • Structure: A p-aminobenzoic acid (PABA) analog.

Para-Aminosalicylic Acid (PASA)

Mechanism of Action

  • Inhibits dihydrofolate reductase (DHFR), disrupting folic acid metabolism.

Uses

  • Second-line treatment for MDR-TB.

Side Effects

  • GI disturbances, hepatotoxicity, hypersensitivity reactions.

Structure-Activity Relationship (SAR)

Structural Feature SAR Insight
Amino group at para-position Essential for antimycobacterial activity; mimics PABA to inhibit dihydropteroate synthase.
Carboxylic acid (COOH) at ortho position Required for activity; interacts with bacterial enzyme system.
Phenolic –OH group Increases solubility and mimics salicylic acid. Important but not absolutely essential.
Any major substitution on benzene ring Typically results in loss of activity.
Methyl esters of PAS May reduce GI side effects while retaining activity.

 

Synthesis of Para-Aminosalicylic Acid (PASA)

Synthesis of Para-Aminosalicylic Acid (PASA)

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