Synthesis and biological activities of 2-aminophenol-based Schiff bases and their structure–activity relationship

Six Schiff bases 8 – 13 were synthesized by condensation of 2-aminophenol ( 1 ) with various chloro- and nitro-benzaldehydes ( 2 – 7 ), characterized, and evaluated for antioxidant, antibacterial, lipoxygenase, and urease inhibitory potentials. All Schiff bases except 11 showed potent antioxidant activity with IC 50 values ranging between 17.2 and 33.1 μM when compared with standard BHA (IC 50 = 44.2 μM); especially, compound 10 (IC 50 = 17.2 μM) and compound 13 (IC 50 = 18.6 μM) exhibited much better potential than the standard BHA. In lipoxygenase inhibition activity, all products except 8 showed excellent-to-good potential with IC 50 values ranging from 22.5 to 110.5 μM while comparing with standard baicalein (IC 50 = 22.6 μM). Compound 10 (IC 50 = 22.5 μM) showed lipoxygenase potential comparable to the standard baicalein (IC 50 = 22.6 μM), and molecular docking simulations showed that nitro group of 10 penetrated deeply into a pocket surrounded by basic amino acid residues which revealed the excellent activity of 10 . All products also showed good potential against all gram-positive S. intermedius, B. subtilis , and S. aureus, and moderate activity against gram-negative E. coli and S. typhi bacteria. However, the products showed nonsignificant inhibitory potential against urease enzyme.