In our ongoing efforts to identify effective natural antiviral agents, four methoxy flavonoids (1–4) were isolated from the Inula britannica flower extract. Their structures were elucidated using nuclear magnetic resonance. Flavonoids 1–4 exhibited inhibitory activity against SARS- CoV-2 3CLpro with IC50 values of 41.6 ± 2.5, 35.9 ± 0.9, 32.8 ± 1.2, and 96.6 ± 3.4 μM, respectively. Flavonoids 1–3 inhibited 3CLpro in a competitive manner. Based on molecular simulations, key amino acids that form hydrogen bond with inhibitor 3 were identified. Finally, we found that inhibitors (1–3) suppressed HCoV-OC43 coronavirus proliferation at micromole concentrations.
Keywords
Inula britannica
Methoxyl flavonoids
SARS-CoV-2
3CLpro
HCoV-OC43
Data availability
No data was used for the research described in the article.