2.6. Surface plasmon resonance assay
The interactions between SARS-CoV-2 Mpro and gallic acid and quercetin for were studied by SPR include immobilizing SARS-CoV-2 Mpro on a CM5 sensor chip surface and then flowing a solution containing the compound over the surface. The sensor surface was activated with a 7 min injection of the mixture of 50 mM N-hydroxysuccinimide (NHS) and 200 mM 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). 10 mM sodium acetate was used as a running buffer. Compounds was diluted to different concentrations and injected over the surfaces at a flow rate of 10 µL/min. The contact time was 90 s, followed by a 180 s dissociation period. All SPR experiments were conducted on Biacore T200 instruments (Cytiva, Sweden). The specific experimental protocol and conditions were performed as described in previous study28,29.