Para-aminobenzoic acid (PABA)

Para-aminobenzoic acid (PABA) is a naturally occurring organic compound and a member of the vitamin B complex, although it is not an essential nutrient for humans [1, 3]. It serves as a vital intermediate in the bacterial synthesis of folic acid, acting as a substrate for the enzyme dihydropteroate synthase (DHPS) [2, 12]. This metabolic pathway is the primary target of sulfonamide antibiotics, which are structural analogs of PABA that competitively inhibit DHPS, thereby preventing bacterial DNA synthesis and growth [12, 16]. PABA is also well-known for its ability to absorb ultraviolet B (UVB) radiation, which led to its widespread historical use as an active ingredient in sunscreens [2, 6]. Clinically, PABA and its potassium salt (Potaba) are used to treat fibrotic skin conditions such as Peyronie's disease and scleroderma, likely by enhancing oxygen uptake in tissues and suppressing fibrosis [1, 8, 16]. Additionally, PABA is utilized as a biomarker to assess the completeness of 24-hour urine collections in clinical research due to its rapid and predictable renal excretion [11, 13]. While generally safe at low doses, high systemic concentrations of PABA can lead to hepatotoxicity and may interfere with the efficacy of sulfa-based medications [1, 8, 16].

Other names

4-Aminobenzoic acidVitamin BxVitamin B10Aminobenzoic acidp-Aminobenzoic acidBacterial Vitamin H1

Competitive inhibition of dihydropteroate synthase (as a substrate analog); UVB radiation absorption; Antifibrotic activity via increased tissue oxygenation