Anti-Infectious Bronchitis Virus (IBV) Activity of 1,8-cineole: Effect on Nucleocapsid (N) Protein

In the present study, anti-IBV (infectious bronchitis virus) activity of 1,8-cineole was studied by MTT assay, as well as docking and molecular dynamic (MD) simulations. The CC50 of 1,8-cineole was above 10 mM. And the maximum noncytotoxic concentration (TD0) of 1,8-cineole was determined to be 3.90 +/- 0.22 mM, which was much higher than that of ribavirin (0.78 +/- 0.15 mM). 1,8-cineole could inhibit IBV with an IC50 of 0.61 mM. MTT assay showed that the inhibition of IBV by 1, 8-cineole appears to occur moderately before entering the cell but much strongly after penetration of the virus into the cell. In silico simulations indicated that the binding site of 1,8-cineole was located at the N terminus of phosphorylated nucleocapsid (N) protein, with interaction energy equaling -40.33 kcal mol(-1). The residues TyrA92, ProA134, PheA137, AspA138 and TyrA140 had important roles during the binding process and are fully or partially conserved in various IBV strains. Based on spatial and energetic criteria, 1,8-cineole inerfered with the binding between RNA and IBW N-protein. Results presented here may suggest that 1,8-cineole possesses anti-IBV properties, and therefore is a potential source of anti-IBV ingredients for the pharmaceutical industry.