Two common wild plants ‘stop COVID-19 from infecting cells’

Two common wild plants offer hope for a botanical extract which could help to treat COVID-19, a new study has shown.

Tests in lab dishes found that flowers of tall goldenrod and a part of eagle fern both blocked SARS-CoV-2 (the virus which causes COVID) from entering human cells.

The researchers warn that self-treating with the herbs would be ineffective and potentially dangerous – the active compounds are only present in tiny quantities, and eagle fern is toxic.

But the finding holds out hope that the plants could form the basis of future medicines to treat COVID-19.

Cassandra Quave, senior author of the study and associate professor in Emory School of Medicine, said: "It's very early in the process, but we're working to identify, isolate and scale up the molecules from the extracts that showed activity against the virus.

"Once we have isolated the active ingredients, we plan to further test for their safety and for their long-range potential as medicines against COVID-19."

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Quave is an ethnobotanist, studying how traditional people have used plants for medicine to identify promising new candidates for modern-day drugs.

Her lab curates the Quave Natural Product Library, which contains thousands of botanical and fungal natural products extracted from plants collected at sites around the world.

Given that COVID-19 is a newly emerged disease, the researchers devised a method to rapidly test more than 1,800 extracts and 18 compounds from the Quave Natural Product Library for activity against SARS-CoV-2.

PhD candidate and lead author Caitlin Risener said: "We've shown that our natural products library is a powerful tool to help search for potential therapeutics for an emerging disease.

“Other researchers can adapt our screening method to search for other novel compounds within plants and fungi that may lead to new drugs to treat a range of pathogens."

SARS-CoV-2 is an RNA virus with a spike protein that can bind to a protein called ACE2 on host cells. "

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The viral spike protein uses the ACE2 protein almost like a key going into a lock, enabling the virus to break into a cell and infect it," Quave explains.

The researchers devised experiments with virus-like particles, or VLPs, of SARS-CoV-2, and cells programmed to overexpress ACE2 on their surface.

The VLPs were stripped of the genetic information needed to cause a COVID-19 infection.

Instead, if a VLP managed to bind to an ACE2 protein and enter a cell, it was programmed to hijack the cell's machinery to activate a fluorescent green protein.

A plant extract was added to the cells in a petri dish before introducing the viral particles. By shining a fluorescent light on the dish, they could quickly determine whether the viral particles had managed to enter the cells and activate the green protein.

Further experiment results confirmed the ability of the tall goldenrod and eagle fern extracts to inhibit the ability of SARS-CoV-2 to bind to a living cell and infect it.

"Our results set the stage for the future use of natural product libraries to find new tools or therapies against infectious diseases," Quave says.

As a next step, the researchers are working to determine the exact mechanism that enables the two plant extracts to block binding to ACE2 proteins.

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