Synthesis and Biological Evaluation of Honokiol Derivatives Bearing 3-((5-phenyl-1,3,4-oxadiazol-2-yl)methyl)oxazol-2(3H)-ones as Potential Viral Entry Inhibitors against SARS-CoV-2.

The 2019 coronavirus disease (COVID-19) caused by SARS-CoV-2 virus infection has posed a serious danger to global health and the economy. However, SARS-CoV-2 medications that are specific and effective are still being developed. Honokiol is a bioactive component from Cortex with damp-drying effect. To develop new potent antiviral molecules, a series of novel honokiol analogues were synthesized by introducing various 3-((5-phenyl-1,3,4-oxadiazol-2-yl)methyl)oxazol-2(3)-ones to its molecule. In a SARS-CoV-2 pseudovirus model, all honokiol derivatives were examined for their antiviral entry activities. As a result, and demonstrated antiviral entry effect with IC values of 29.23 and 9.82 µM, respectively. However, the parental honokiol had a very weak antiviral activity with an IC value more than 50 µM. A biolayer interfero-metry (BLI) binding assay and molecular docking study revealed that binds to human ACE2 protein with higher binding affinity and lower binding energy than the parental honokiol. A competitive ELISA assay confirmed the inhibitory effect of on SARS-CoV-2 spike RBD's binding with ACE2. Importantly, and (TC > 100 μM) also had higher biological safety for host cells than honokiol (TC of 48.23 μM). This research may contribute to the discovery of potential viral entrance inhibitors for the SARS-CoV-2 virus, although 's antiviral efficacy needs to be validated on SARS-CoV-2 viral strains in a biosafety level 3 facility.