Two plants that can be found throughout North American wilderness contain ingredients that can block the virus that causes COVID-19 from entering human cells, a recent study says.
After testing 1,867 samples extracted from different parts of 660 plant and fungal species, a team of scientists at Emory University in Georgia reported that extracts from the flowers of tall goldenrod (Solidago altissima) and the rhizomes of the eagle fern (Pteridium aquilinum) each prevented the viral spike protein of SARS-CoV-2 from attaching to human cells in lab settings.
Both plants are native to North America. In fact, they are known to be used by Native American peoples as herbal remedies, the scientists noted.
Tall goldenrod flowers were reported to be used as burn dressings and applied to ulcers by the Ojibwe tribe, according to the study. Meanwhile, eagle fern is part of the diet across many indigenous tribes and has a long history of varied uses including antiseptic and anthelminthic.
With that said, the scientists advised against people trying to treat COVID with the plants, considering that actually effective compounds are only present in minuscule quantities in the plants. Not to mention that all parts of eagle fern are toxic.
“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,” Cassandra Quave, the study’s co-author and a botanist specialized in traditional medicine at Emory University, said in a press release. “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.”
Studies show that COVID enters by binding its spike protein to a receptor, called ACE2, on the surface of the host cell. “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 said.
For their experiment, Emory scientists used virus-like particles (VLPs), which are COVID-based viruses stripped of the genetic information needed to cause infection; and human cells programmed to overexpress ACE2 on their surface. The VLP was programmed in a way that once it successfully bonded to an ACE2 protein and made entry, it would produce a fluorescent green protein.
Scientists added a plant extract to the cells in a petri dish before introducing the VLPs. They then shined a fluorescent light on the dish to see if the VLP had made it into the cells and produced the green protein.
Tall goldenrod and eagle fern extract both “demonstrated robust activity at lower concentrations, as well as minimal cytotoxicity at higher concentrations,” according to the study. They also showed antiviral effects in COVID-infected cell culture.
“Plants have such chemical complexity that humans probably couldn’t dream up all the botanical compounds that are waiting to be discovered,” said Caitlin Risener, the study’s leading author. “The vast medicinal potential of plants highlights the importance of preserving ecosystems.”
The study was published in Scientific Reports on Jan. 23.