5-Amino salicylic acid inhibits nitrite-induced methemoglobin formation

5 Amino salicylic acid (5-ASA) and several structurally-related analogs were tested for inhibitory role on nitrite-induced oxidation of hemoglobin in human blood-hemolysates. Results indicate a strong inhibitory role for 5-ASA in a concentration range of 0.2 to 0.8 mM. Although the inhibitory activity of 5-ASA was higher than other structural alalogs tested, the activity of curcumin was much higher at equimolar levels. PABA also showed some activity at similar concentrations although it was lower than that of 5-ASA. Benzoic acid showed marginal activity at lower concentrations. On the other hand, acetyl salicylic acid and salicylic acid increased the methemoglobin levels in hemolysate. The pro-oxidant activity was higher at higher concentrations for these compounds. Higher level of activity of 5-ASA is consistent with previous findings. As acetyl salicylic acid and 5-ASA are currently being prescribed, it is worth investigating their in vivo activity in order to establish novel and hitherto unexplored clinical applications.