Para-aminobenzoic acid scavenges reactive oxygen species and protects DNA against UV and free radical damage
✍ Scribed by Miao-Lin Hu; Yang-Kang Chen; Ling-Chun Chen; Mitsuaki Sano
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 521 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0955-2863
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✦ Synopsis
Para-aminobenzoic acrd (PABA). once considered a ~~rttrmln. l.s a precursor of folate for certain bacteria and is used as a sunscreen because of its UV-absorbing proper?. In addition to its mild anti-injlammaton: activity, recent studies demonstrate that PABA protects again.st photoc,urcYnogenesis in hairless mice and nephrotoxicity of cis-diamminedichloroplatinum(ll) in ratJ. Howe,er. lrttle is known regarding the mechanism by which PABA exerts these effects. We have hypothesized that PABA may be an eflective scavenger of reactive oxygen species. In this report, we showed that PABA rewted with hypoc,hlorite in a ratio of reaction of 1:2. as measured bq' a spectrofluorometric method det,eloped in this study. PABA reacted with hydroxyl radicals (.OH) by inhibiting deoxyibose oxidation induced bx a Fenton-epe reactron .ystem (Fe-' * f EDTAiH,Ozlascorbic acid). The second-order rate constant for the reaction of PABA ,czlth .OH +tas upproximately I .07 X 1O'o M-' s-'. Electron spin resonance studies further demonstrated the reac,tion of PABA with .OH. The Fenton-epe reaction system also caused damage to calf thymus DNA, and concurrent treatment bvith L'V (254 nm) enhanced the damage b! 3 fold. PABA tested ut I .O mM afforded 58% protection against such damage. Using rose bengal as a singlet oxygen ('0,) generator and ESR technrques, we showed that PABA scavenged '0, more effectively than sodium azide, a known quencher of 'Oz. However. PABA did not scavenge supero.ride anions or react with H,O,. Thus, in addition to its L/V absorbing ability, PABA effectiveIF scatzenges certain reactive oxygen species, an effect that may be relevant to Its protection against photoc~cln~inogenesrs, inflammation, and drug toxicity. (J.