Discovery of Chalcone Derivatives as Bifunctional Molecules with Anti-SARS-CoV-2 and Anti-inflammatory Activities.

Danshensu extracted with traditional Chinese medicine Salvia miltiorrhiza has a wide range of bioactivities. Danshensu containing a catechol moiety has a moderate inhibitory effect on SARS-CoV-2 3CL^pro (IC₅₀ = 2.2 μM) by a reversible covalent interaction and exhibits good anti-inflammatory activity. To enhance the inhibitory activity, we introduced Michael receptors into the side chain of danshensu as a possible covalent warhead and blocked the covalent binding sites of catechol moiety to yield chalcone derivatives. The resulting chalcone derivatives, A4 and A7, were found to inhibit SARS-CoV-2 3CL^pro in vitro with IC₅₀ values of 83.2 and 261.3 nM, respectively. Furthermore, A4 and A7 inhibit viral replication in the SARS-CoV-2 replicon system with EC₅₀ values of 19.9 and 11.7 μM, respectively. Time-dependent inhibition experiment and mass spectrometry show that A4 acted as a noncovalent mixed inhibitor, while A7 likely binds covalently at Cys145. The interaction mechanism between SARS-CoV-2 3CL^pro and A4 or A7 was characterized by molecular docking studies. Additionally, both A4 and A7 demonstrated potent anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. These promising results suggest that chalcone derivatives A4 and A7 can serve as bifunctional molecules with both antivirus and anti-inflammatory properties.