Anti-coronavirus and anti-pulmonary inflammation effects of iridoids, the common component from Chinese herbal medicines for the treatment of COVID-19

The practice of Chinese herbal medicines for the treatment of COVID-19 in China played an essential role for the control of mortality rate and reduction of recovery time. The iridoids is one of the main constituents of many heat-clearing and detoxifying Chinese medicines that were largely planted and frequently used in clinical practice. Twenty-three representative high content iridoids from several staple Chinese medicines were obtained and tested by a SARS-CoV-2 pseudo-virus entry-inhibition assay on HEK-293 T/ACE2 cells, a live HCoV-OC43 virus infection assay on HRT-18 cells, and a SARS-CoV-2 3CL protease inhibitory FRET assay followed by molecular docking simulation. The anti-pulmonary inflammation activities were further evaluated on a TNF-α induced inflammation model in A549 cells and preliminary SARs were concluded. The results showed that specnuezhenide (7), cornuside (12), neonuezhenide (15), and picroside III (21) exhibited promising antiviral activities, and neonuezhenide (15) could inhibit 3CL protease with an IC₅₀ of 14.3 μM. Docking computation showed that compound 15 could bind to 3CL protease through a variety of hydrogen bonding and hydrophobic interactions. In the anti-pulmonary inflammation test, cornuside (12), aucubin (16), monotropein (17), and shanzhiside methyl ester (18) could strongly decrease the content of IL-1β and IL-8 at 10 μM. Compound 17 could also upregulate the expression of the anti-inflammatory cytokine IL-10 significantly. The iridoids exhibited both anti-coronavirus and anti-pulmonary inflammation activities for their significance of existence in Chinese herbal medicines, which also provided a theoretical basis for their potential utilization in the pharmaceutical and food industries.