Para-Aminosalicylic Acid (PASA)
- BP-S-6-Medicinal Chemistry III
- Mar 29
- 1 min read
Chemical Structure / Formula of Para-Aminosalicylic Acid (PASA)
Formula: C7H7NO3
Structure: A p-aminobenzoic acid (PABA) analog.
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. |
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. |
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. |
Synthesis of Para-Aminosalicylic Acid (PASA)
