An extract from willow bark shows high potential as an agent against viral infections. Various active ingredients for medicines have already been obtained from the bark of willow trees, including salicin, the precursor to modern aspirin.
A Finnish research team led by Prof. Varpu Marjomäki from the University of Jyväskylä has investigated the antiviral potential of hot water extracts from willow bark against coronaviruses and enteroviruses and published the promising results in the specialist journal “Frontiers in Microbiology”.
Looking for anti-virus drugs
From a seasonal cold to gastrointestinal infections, viruses can cause a wide variety of illnesses and result in dangerous epidemics. Drugs that work against a broad spectrum of viruses are not yet available.
However, in cell sample experiments, the researchers now tested the effect of a willow bark extract against enveloped coronaviruses, which cause both colds and COVID-19, and against non-enveloped enteroviruses, which can cause various diseases from colds to meningitis.
In previous studies, the researchers had already successfully tested the effect of willow bark extract against enteroviruses, and in the new study, additional viruses were added. The team also tried to understand the mechanism of action of the extract.
The extract was made from the bark of willow branches, which was cut into pieces, frozen, ground and then extracted with hot water, the team explains. The researchers tested its antiviral effect on cell cultures.
Effective protection against infections
Among other things, they determined how long it took for the extract to act on infected cells and how well it inhibited virus activity. The experts explain that it has been shown that the extract does not harm the cells, but effectively protects them from infections.
In the case of SARS-CoV-2, the pathogen that causes COVID-19, the researchers also found that this virus penetrated the cells despite treatment with the extract, but was unable to multiply there.
Overall, the study makes it clear that willow bark extract can work against two differently structured virus types, although the mechanism of action appears to be very different because treated enteroviruses were unable to penetrate cells, according to the research team.
In subsequent studies, the team examined the role played by the timing of adding the extract to understand whether the extract attacks specific phases of the virus life cycle. It turned out that the extract apparently worked on the surface of the virus and not at a specific stage of its replication cycle.
Furthermore, microscopic examinations made it clear that the coronaviruses were broken down, while the enteroviruses were apparently locked up and prevented from releasing their genome and reproducing, the researchers explain.
Revolutionary new antiviral therapies?
“The extracts worked against different viruses via different mechanisms, but were equally effective in inhibiting enveloped and non-enveloped viruses,” emphasizes Prof. Marjomäki. The success of the willow bark extract is probably based on the interaction of various bioactive compounds.
Further research is now required to understand the bioactive compounds involved, their chemical structure and how they work. The researchers hope that this could potentially lead to revolutionary new antiviral treatments. (fp)