Myricetin Inhibits SARS-CoV-2 Viral Replication by Targeting Mpro and Ameliorates Pulmonary Inflammation

Abstract

The coronavirus disease 2019 (COVID-19) has spread widely around the world and has seriously affected the human health of tens of millions of people. In view of lacking anti-virus drugs target to SARS-CoV-2, there is an urgent need to develop effective new drugs. In this study, we reported our discovery of SARS-CoV-2 M^pro inhibitors. We selected 15 natural compounds, including 7 flavonoids, 3 coumarins, 2 terpenoids, one henolic, one aldehyde and one steroid compound for molecular docking and enzymatic screening. Myricetin were identified to have potent inhibit activity with IC₅₀ 3.684 ± 0.076 μM in the enzyme assay. The binding pose of Myricetin with SARS-CoV-2 M^pro was identified using molecular docking method. In the binding pocket of SARS-CoV-2 M^pro, the chromone ring of Myricetin interacts with His41 through π-π stacking, and the 3'-, 4'- and 7-hydroxyl of Myricetin interact with Phe140, Glu166and Asp187 through hydrogen bonds. Significantly, our results showed that Myricetin has potent effect on bleomycin-induced pulmonary inflammation by inhibiting the infiltration of inflammatory cells and the secretion of inflammatory cytokines IL-6, IL-1α, TNF-α and IFN-γ. Overall, Myricetin may be a potential drug for anti-virus and symptomatic treatment of COVID-19.

Keywords: 3CLpro (Mpro); COVID-19; SARS-CoV-2; myricetin; pulmonary inflammation.

FIGURE 1

Screening of natural compounds against SARS-CoV-2 M^pro and the inhibitory activity of Myricetin in vitro. (A). 50 μM compound was pre-incubated with 0.3 μM SARS-CoV-2 M^pro at 37°C for 10 min, and then 20 μM FRET substrate was added to the reaction mixture to initiate the reaction. The excitation wavelength is 340 nm and the emission wavelength is 490 nm for fluorescence measurement. Results Inhibition rate (%) = (RFU100% enzyme activity control-RFU sample)/(RFU100% enzyme activity control-RFU blank control) × 100%. The results are average ± standard deviation of three repeats. (B) The inhibitory assay of Myricetin show efficient inhibition for M^pro. Error bars: mean ± S.D. of three independent replicates.

FIGURE 2

The binding mode of Myricetin in SARS-CoV-2 Mpro. Hydrogen bonds and π-π interactions between Myricetin and SARS-CoV-2 M^pro are represented by dashed lines.

FIGURE 3

Myricetin reduces the inflammatory response in BLM-treated mice. (A) Dosing regimen in BLM-induced inflammatory model. (B–C) H&E staining of left lung tissues (B, Scale: 50 μm) and inflammatory cells in BALF (C, Scale: 20 μm) of each group. (D) Total number of cells from BALF in each group. (E) Counts of macrophages in BALF. (F) Counts of lymphocytes in BALF. (G) Counts of Neutrophiles in BALF. (H–K) The expression of inflammatory factors including IL-6, IL-1α, TNF-α and IFN-γ in BALF were detected by ELISA. Data are shown as mean ± SD. # represent the difference between NaCl and BLM-treated group, ##P < 0.01, ###P < 0.001, ####P < 0.0001. * represent the difference between BLM-treated and treatment group, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.