Researchers in Finland have discovered that willow bark extract has powerful antiviral properties against a variety of viruses, including COVID-19 and enteroviruses, providing a promising basis for the development of new antiviral treatments.
From seasonal colds to stomach bugs, viral infections are decidedly unwelcome, and epidemics can have catastrophic effects. To combat future outbreaks, the development of safe and sustainable antiviral therapies is critical. Researchers in Finland recently discovered that willow bark extract showed broad antiviral effects in laboratory cell studies. Willow bark extract is a plant known for producing a variety of medicinal compounds, including the basis for contemporary aspirin.
The extract is effective against both enveloped coronaviruses, which cause colds and COVID-19, and non-enveloped enteroviruses, which cause infections such as influenza and meningitis. There are currently no clinically approved drugs that directly target enteroviruses, so this extract could be a game-changer in the future.
Professor Varpu Marjomäki of the University of Jyväskylä, senior author of the study, said in the journal Frontiers in Microbiology: "We need broad and highly effective tools to combat the viral load in daily life. Vaccinations are important, but they alone will not be effective against many emerging serotypes."
Scientists have previously tested willow bark extract against enteroviruses and found it highly successful: in this new study, they expanded their research to look at a wider variety of viruses and tried to understand how the extract worked.
To make the extract, they harvested branches from commercially grown willow trees. The bark is cut into pieces, frozen, ground, and then extracted with hot water. This resulted in extract samples, which the scientists tested against enteroviruses (coxsackievirus strains A and B) and coronaviruses (seasonal coronavirus and COVID-19).
The scientists used cytopathic effect inhibition assays to observe how long the extract acted on infected cells and how much it inhibited viral activity. This extract does not harm the cells themselves and effectively protects them from infection. Binding tests on COVID-19 samples further showed that while the virus was able to enter cells even after being treated with extracts, it was unable to reproduce once inside.
The authors had previously found that this extract was effective against enteroviruses, meaning it worked against two different structural types of viruses (enveloped and non-enveloped). However, the mechanism of action appears to be very different, as the treated enterovirus is unable to enter cells.
The scientists then experimented with when the extract was added to see if it could attack specific stages of the virus' life cycle. They found that the extract appeared to act on the surface of the virus rather than on any specific stage of the virus's replication cycle.
They also looked at the treated viruses under a microscope to better understand the extract's effects. Both viruses clump together rather than spread out, but the enveloped coronavirus appears to be broken down, while the non-enveloped enterovirus appears to be locked in, preventing it from releasing its genome and reproducing.
"These extracts act on different viruses through different mechanisms," says Marjomäki. "But the extracts are equally effective at inhibiting enveloped and non-enveloped viruses."
The authors also tested existing medical compounds extracted from willow bark, as well as commercially prepared salixanthin extracts and salixanthin powders. Of these, only the salvianoside extract showed antiviral activity, suggesting that the scientists' success with the willow bark extract may be the result of the interaction of different bioactive compounds.
Scientists fractionated the extract to understand its chemical composition, but did not get a clear answer as to which of the many potent compounds might be responsible for the antiviral effects. Further research is needed to understand the bioactive compounds, their chemical structures and how they work, so that it may be possible to develop revolutionary new antiviral treatments.
"We are currently continuing with the fractionation and identification of bioactive molecules in willow bark extracts," says Marjomäki. "This will provide us with a large number of identified pure molecules, which we can study in further detail. In addition, we will use the purified components to study more viruses. The purified components will give us a better opportunity to study their mechanisms of action."
Compiled source: ScitechDaily