Pyrazole derivatives of medically relevant phenolic acids: Insight into antioxidative and anti-lox activity

Abstract

Background: From the point of view of medicinal chemistry, compounds containing phenolic and pyrazolic moiety are significant since they are often constituents of bioactive compounds. Objective: The aims of this study were to synthesize pyrazole derivatives of medically relevant phenolic acids, confirm their structure, and evaluate their antioxidative and anti-LOX activities. Methods: Phenolic pyrazole derivatives were obtained, starting from esters of medically relevant phenolic acids. The structures of all obtained compounds were determined by NMR and IR spectroscopy, and UV-Vis spectrophotometry. In addition, the single-crystal X-ray diffraction was used. Pyrazole derivatives were tested for their in vitro antioxidative (DPPH assay), and lipoxygenase (LOX) inhibitory ac-tivities. Radical quenching mechanism was estimated using DFT and thermodynamic approach, while molecular docking was used to estimate the binding mode within the enzyme. Results: Pyrazole derivatives were obtained in high yields. The crystal structure of a new compound 3e was determined. Pyrazole derivative with catechol moiety 3d exhibited excellent radical scavenging ac-tivity, while compound 3b exhibited the best anti-LOX activity. Molecular docking study revealed that there is no direct interaction of any ligand with the active site of LOX-Ib, but pyrazoles 3a-e behave as inhibitors blocking the approach of linoleic acid to the active site. Conclusion: In this research, protocatechuic and vanillic acid pyrazole derivatives have been obtained for the first time. In vitro antioxidative assay suggests that pyrazole derivate of protocatechuic acid is a powerful radical scavenger, while anti-LOX assay indicates a pyrazole derivative with 4-hydroxyphenyl moiety.