Discovery of Novel Pyrazole Derivatives as Potent Neuraminidase Inhibitors against Influenza H1N1 Virus

Ten pyrazole derivatives were synthesized and evaluated for their ability to inhibit the replication of influenza virions. All the compounds were synthesized in good-to-excellent yield, and the structures were ascertained with the help of (1) H NMR, (13) C NMR, mass, and elemental analysis. Among the tested series, compound 4i was identified as the most potent analog against the H1N1 virus, with IC50 = 5.4 µM, while the rest of the compounds showed mild-to-moderate inhibition of infection. Moreover, these compounds showed excellent inhibitory activity against influenza A neuraminidase (NA), with IC50 values ranging from 2.15 to 7.54 µM, among which compound 4i showed the most prominent inhibition with IC50 = 1.32 µM. To further exemplify the molecular contacts with NA, a molecular docking study of 4i was conducted with the 3D crystal structure of enzyme H5N1-NA in complex. Results showed that target molecules interact in a similar fashion with oseltamivir and zanamivir by creating interatomic contacts with Trp178, Glu227, and Arg371. Moreover, in the toxicity assay with the porcine renal proximal cell line, LLC-PK1, the confocal images showed no appreciable change in morphological character at the highest tested dose.