A compound found in the bark of magnolia tree inhibits reproduction of the SARS-CoV-2 virus, which causes COVID-19, in several types of cells, and may be effective against future coronaviruses, according to a study.
The researchers found that the compound called honokiol caused the production of infectious SARS-CoV-2 viral particles in treated cells to fall to around 1,000th of the previous level.
The research, published in the journal Microbiology Spectrum, also shows that the compound inhibited replication of other highly pathogenic human coronaviruses, including Middle East respiratory syndrome (MERS) and Severe acute respiratory syndrome (SARS).
"This suggests that it has a broad spectrum of activity and would likely also inhibit novel coronaviruses that might emerge in the future," said Martijn J. van Hemert, Associate Professor at Leiden University in The Netherlands.
"If honokiol can be developed into a drug, possibly in combination with other compounds, stockpiling it would help us to increase our preparedness for the emergence of the next coronavirus," said van Hemert.
Broad-spectrum drugs could then be used to treat early patients and prevent spread, or they could be used prophylactically among healthcare workers, and in high-risk groups, such as among nursing home residents, the researchers said.
Honokiol also has anti-inflammatory properties that could be helpful in cases where patients wait until a relatively late stage of the disease to obtain medical treatment, by which time the body's own inflammatory responses to the infection are causing symptoms, van Hemert noted.
"At that point, inhibition of virus replication might no longer be helpful, but honokiol's anti-inflammatory response might mitigate the illness," van Hemert explained.
Honokiol inhibits a later step of the viral replication cycle -- one that takes place after the virus has entered the cell.
The researchers suspect that honokiol does so by triggering processes in the host cell that impede replication of the virus. It did so in the case of the original SARS-CoV-2 variants, and also in that of the more recent Omicron variants.
"Our study merely provides the basis for further research into potential therapeutic applications,” said van Hemert.
"It is important to mention that it is too early to claim that honokiol might be used in SARS-CoV-2 patients. This requires much more research and -- if successful -- properly conducted clinical trials," the researcher added.
