Synthesis and biological evaluation of tetrazole derivatives as TNF-α, IL-6 and COX-2 inhibitors with antimicrobial activity: Computational analysis, molecular modeling study and region-specific cyclization using 2D NMR tools.

A group of tetrazole bearing compounds were synthesized and evaluated for their in vitro cyclooxygenase (COX) isozymes (COX-1/COX-2) inhibitory activity, in vitro anti-inflammatory activity through measuring levels of expression of IL-6 and TNF-α and antimicrobial activity. Cyclization of pyridine derivative 5b was confirmed using 2D NMR such as NOESY and HMBC experiments. Within the synthesized compounds, compound 7c was identified as effective and selective COX-2 inhibitors (COX-2 IC50 = 0.23 uM; COX-2 selectivity index = 16.91). Moreover 7c was the most effective derivative on TNF-α (37.6 pg/ml). While, the most active compound on IL-6 was isoxazole derivative 6 (42.8 pg/ml). Dual inhibitory activity on both IL-6 and TNF-α was exhibited by compounds 2 and 3 (IL-6 = 47.5 and 82.7 pg/ml, respectively) and (TNF-α = 31.7 and 33.8 pg/ml, sequentially). Additionally, compound 7a, showed broad spectrum antimicrobial activity against Gram positive cocci, Gram positive rods and yeast fungus (inhibition zone = 20 and 19 mm). None of the test compounds exhibited activity against Gram negative rods. Compounds 3 and 7c exhibited good antifungal activity at MIC equal to 64.5 µg/ml. While compound 6 showed antibacterial activities against Micrococcus lysodicticus and Bacillus subtilis at MIC = 32.25 and 64.5 µg/ml, respectively. Computational analysis was used to predict molecular properties and bioactivity of the target compounds. To confirm the mode of action of the synthesized compounds as anti-inflammatory agents, molecular docking was done. Appreciable binding interactions were observed for compound 7c containing COX-2 pharmacophore (SO2NH2), with binding energy -10.6652 Kcal/mol, forming two hydrogen bonding interactions with His90 and Tyr355 amino acids. It was fully fitted within COX-2 active site having the highest COX-2 selectivity index between all the test compounds (S.I. = 16.91).