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Magnolia tree compound may be effective against the next coronavirus

A team of scientists led by Leiden University in the Netherlands has recently discovered that a compound called honokiol, which is found in the bark of various species of magnolia tree, inhibits the replication of SARS-CoV-2 in several types of cells, causing the production of infectious viral particles to drop to around 1,000th of their previous levels.

“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 Martijn J. van Hemert, an associate professor of Medical Microbiology at Leiden. “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.”  

Experiments on cultured cells revealed that this natural compound also inhibited the replication of other highly pathogenic coronaviruses, such as MERS-CoV and SARS-CoV-1. “This suggests that it has a broad spectrum of activity and would likely also inhibit novel coronaviruses that might emerge in the future,” Hemert said.

Honokiol inhibits a later step of the viral replication cycle, taking place after the virus has entered the cell, by triggering processes in the host cell that stop the replication of the virus. This mechanism of action was observed both in the case of the original SARS-CoV-2 strain, and in the case of more recent Omicron variants.

According to the experts, honokiol also has anti-inflammatory properties and could thus be helpful in cases where patients wait until a relatively late stage of the disease before seeking treatment, by which time the body’s inflammatory responses to the infection are starting to cause significant harm. While at that point, the inhibition of virus replication might no longer be helpful, this compound’s anti-inflammatory response may still alleviate the illness.

“Our study merely provides the basis for further research into potential therapeutic applications. 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,” Van Hemert concluded.

The study is published in the journal Microbiology Spectrum

More about magnolia trees

Magnolias are an ancient genus of flowering plants. They are named after the French botanist Pierre Magnol and are known for their large, fragrant blossoms. Here are some key facts about magnolia trees:


There are more than 200 species of magnolias that are native to both Asia and the Americas. They come in many forms, from large trees to small shrubs, and they are evergreen or deciduous.


The flowers are perhaps the most distinctive feature of the magnolia tree. They are large and fragrant, with many species producing white, pink, purple, or yellow flowers. Some magnolias, like the Southern magnolia (Magnolia grandiflora), bloom throughout the summer, while others, like the star magnolia (Magnolia stellata), flower in the early spring before their leaves appear.

Fossil Records

Magnolias are among the most ancient flowering plants. Fossil records show that magnolia plants were around 95 million years ago and may have existed even before bees. Their flowers evolved to encourage pollination by beetles, which were among the earliest pollinators.


Different species of magnolias are hardy to different climatic zones. For instance, the Southern magnolia is a hardy tree native to the southeastern United States that can withstand heat and humidity, while the saucer magnolia (Magnolia x soulangeana) is more suited to cooler climates.


Magnolias have various uses. The bark of some species is used in traditional Chinese medicine. They are also popular ornamental trees in parks and gardens due to their attractive and aromatic flowers. Magnolia grandiflora, in particular, is a popular street tree in temperate climates.

Growth and Care

Magnolias prefer slightly acidic, well-drained soil and a sunny or partially shaded location. They do not like to be transplanted once established, so it’s essential to plant them in a suitable location from the start.


In many cultures, magnolias are symbols of beauty, perseverance, and nobility. In the American South, for instance, the magnolia often symbolizes Southern hospitality.

Using plants to fight viruses

Using plants to fight against viruses can be a multifaceted strategy with various approaches. Here are some of the ways plants can be instrumental in viral treatments and pandemic preparedness:


Many plants possess antiviral properties. For instance, Echinacea is known for its immune-boosting and antiviral properties to fight off cold and flu viruses. Likewise, garlic, ginseng, and licorice have shown antiviral effects against several types of viruses. The active compounds within these plants could be isolated and used as a base for developing new antiviral drugs.

Plant-Based Vaccines

Scientists are looking at using plants as “bioreactors” to produce vaccines. A notable example is the tobacco plant. Scientists insert the gene for a viral protein into the plant, and the plant then produces that protein which can be used as a vaccine. This is a cost-effective and scalable way to produce vaccines. For instance, in the case of COVID-19, scientists developed a candidate vaccine using this method.

Plant-Derived Antiviral Proteins

Certain plants produce proteins called antiviral resistance (AVR) proteins that help them resist viral infections. Researchers are exploring the potential of these proteins in treating human viral infections.

RNA Interference (RNAi)

This is a biological process where RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules. Plants commonly use RNAi for their defense against viruses. This knowledge is used to develop antiviral therapies in humans.

Traditional Medicine and Ethnobotany

Various cultures around the world have used plants to treat viral infections for centuries. By studying these traditional practices, scientists may be able to discover new antiviral compounds.

Bioinformatics and Phylogenetics

These are methods used to predict potential antiviral compounds in plants. Researchers can analyze the genetic makeup of plants to predict their potential antiviral properties. These predictions can then be tested in the laboratory.

Antiviral Surface Coatings

Researchers are exploring plant-derived compounds to create antiviral surface coatings. These can be used on high-touch surfaces to reduce viral transmission.


By Andrei Ionescu, Staff Writer

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