Synthesis, Molecular Modelling and In Vitro Anti-inflammatory Activity of Novel 1,2,4-Triazolo[4,3-a]quinoxaline Derivatives

In this study, a series of 12 new 1,2,4-triazolo[4,3-a]quinoxalines (3 a-l) were synthesized to investigate their anti-inflammatory activities. An efficient method for synthesis of 1,2,4-triazolo[4,3-a]quinoxaline compounds (3 a-l) rendered a cyclo-condensation between iminoester derivatives (Compounds 1 a-l) and 1-(quinoxalin-2-yl)hydrazine (Compound 2). The synthesized compound's structural elucidation was carried out using H-1- and C-13-NMR, Mass analysis. Cytotoxicity profiles of the title compounds were assessed by MTT assay, and anti-inflammatory activities were investigated by determining nitrite levels in LPS-induced RAW264.7 murine macrophage cells. In addition, the ability of the compounds to reduce nitrite levels was modelled using molecular docking method. Compound 3 a-l showed good anti-inflammatory activities. Compound 3 f exhibited the most remarkable nitrite-reducing effect (65.12 +/- 1.62 %), which was similar to the nitrite inhibition seen with IND (63.83 +/- 4.20 %) compared to LPS-induced control. Besides, 3 f was followed by 3 i and 3 g, causing a significant decline in nitrite levels (51.56 +/- 8.68 % and 51.13 +/- 8.29 %, respectively). Molecular docking studies predicted that the compounds showed high affinity and formed key interactions with the active site of inducible nitric oxide synthase (iNOS), a key enzyme responsible for elevated nitrite levels. Thus, the current study explored a new series of 1,2,4-triazolo[4,3-a]quinoxaline analogs with promising nitrite-reducing effects, most probably due to iNOS inhibition.