An Emory University study found that extracts from two common wild plants reduce the virus’s ability to infect living cells.
The findings were reported in Scientific Reports as the first major screening of botanical extracts for SARS-CoV-2 viral efficacy. Extracts from the blooms of tall goldenrod (Solidago altissima) and the rhizomes of eagle fern (Pteridium aquilinum) each prevented SARS-CoV-2 from entering human cells in laboratory dish experiments. Plants contain just trace amounts of the active chemicals. People attempting to treat themselves with them would be futile and perhaps hazardous, according to the study. They caution that the eagle fern is known to be harmful.
“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,” said Cassandra Quave, senior author of the study and associate professor in Emory School of Medicine’s Department of Dermatology and the Center for the Study of Human Health, adding, “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.”
Quave is an ethnobotanist who studies how indigenous peoples used plants for healing in order to find viable new medication prospects. Her lab is in charge of the Quave Natural Product Library, which houses thousands of botanical and fungal natural products isolated from plants collected across the world.
The latest paper’s primary author is Caitlin Risener, a PhD candidate in Emory’s Molecular and Systems Pharmacology graduate programme and the Center for the Study of Human Health.
Previously, the Quave lab focused on plants that traditional people had used to treat skin irritation in order to find promising compounds for the treatment of drug-resistant bacterial infections. Because Covid-19 is a novel illness, the researchers used a comprehensive approach.
They developed a technique for speedily testing over 1,800 extracts and 18 compounds from the Quave Natural Product Library for SARS-CoV-2 activity. “We’ve shown that our natural products library is a powerful tool to help search for potential therapeutics for an emerging disease,” Risener said, adding, “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 may connect to a protein on host cells called ACE2. “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 designed studies using SARS-CoV-2 virus-like particles, or VLPs, and cells modified to overexpress ACE2 on their surface. The VLPs were stripped of the genetic material required to infect Covid-19. Instead, if a VLP was able to connect to an ACE2 protein and enter a cell, it was programmed to hijack the cell’s machinery, causing a fluorescent green protein to be activated.
Before injecting the virus particles, a plant extract was applied to the cells in a petri dish. They could rapidly tell whether the viral particles had entered the cells and activated the green protein by placing a fluorescent light on the dish.
The researchers found a few hits for extracts that protect against viral entrance and then focused on the ones with the highest activity: tall goldenrod and eagle fern. Both plant species are native to North America and have long been used for medical purposes by Native Americans.
Additional tests revealed that the plant extracts’ protective capacity was effective against all four SARS-CoV-2 variants: alpha, theta, delta, and gamma. The Quave lab collaborated with co-author Raymond Schinazi, Emory professor of paediatrics, director of Emory’s Division of Laboratory of Biochemical Pharmacology, and co-director of the HIV Cure Scientific Working Group within the NIH-sponsored Emory University Center for AIDS Research, to further test these findings.
Schinazi is a world expert in antiviral research, well recognised for his groundbreaking work on breakthrough HIV medications. Because of the Schinazi lab’s superior biosecurity rating, the researchers were allowed to test the two plant extracts in trials utilising infectious SARS-CoV-2 virus instead of VLPs. The findings validated the potential of tall goldenrod and eagle fern extracts to block SARS-ability CoV-2’s to attach to and infect live cells.
“Our results set the stage for the future use of natural product libraries to find new tools or therapies against infectious diseases,” Quave said. The researchers are now attempting to pinpoint the precise method through which the two plant extracts inhibit ACE2 protein binding.
One of the most enjoyable aspects of the endeavour for Risener was collecting samples of tall goldenrod and eagle fern herself. The Quave lab, in addition to collecting medicinal plants from throughout the world, does field visits to the woods of the Joseph W. Jones Research Center in South Georgia. The Woodruff Foundation built the institute to help maintain one of the few remains of the once-dominant southern longleaf pine ecosystem.
“It’s awesome to go into nature to identify and dig up plants,” Risener said, adding, “That’s something that few graduate students in pharmacology get to do. I’ll be covered in dirt from head to toe, kneeling on the ground and beaming with excitement and happiness.”
She also helps to prepare plant extracts and mount specimens for the Emory Herbarium. “When you collect a specimen yourself, and dry and preserve the samples, you get a personal connection,” she said, adding, “It’s different from someone just handing you a vial of plant material in a lab and saying, ‘Analyze this.'”
Risener plans to pursue a career in outreach and education for science policy related to natural chemical research after graduation. Some of the more well-known botanical medications include aspirin (derived from the willow tree), penicillin (derived from fungus), and the cancer treatment Taxol (from the yew tree).
“Plants contain such chemical complexity that humans probably couldn’t imagine of all the botanical chemicals that are yet to be found,” Risener said, adding, “The huge therapeutic potential of plants underscores the need of ecosystem preservation.”
