Beyond aspirin: Willow bark also found to be a broad-spectrum antiviral

Amazing stuff! The article below dates back to November 2023.

"Now, a Finnish study led by researchers ... has found that willow bark extract might also be an effective, broad-spectrum antiviral agent. ...

In a previous study, the researchers had tested willow bark (Salix) extract on non-enteroviruses, a group of RNA viruses such as those that cause polio and hepatitis A, and found it to be very effective and non-toxic.  ...

The researchers then tested it on cell samples with two strains of enteroviruses, Coxsackievirus A (CVA) and B (CVB), and two coronaviruses, a seasonal coronavirus and SARS-CoV-2, which causes COVID-19. ...
The researchers found that the Salix extract exhibited different mechanisms of action on different virus types. Enteroviruses couldn’t enter cells after they’d been treated with the extract; in the SARS-CoV-2 samples, the virus could enter the treated cells, but it couldn’t reproduce once inside. ...

When the researchers experimented with the timing of adding the extract, they found that it appeared to act on the virus’ surface rather than at a particular stage of its replication cycle. ...

As yet, the researchers have been unable to ascertain which compounds in the extract produce the antiviral effect, so further research will be needed. ..."

From the abstract:

"Introduction: Recurring viral outbreaks have a significant negative impact on society. This creates a need to develop novel strategies to complement the existing antiviral approaches. There is a need for safe and sustainable antiviral solutions derived from nature.

Objective: This study aimed to investigate the antiviral potential of willow (Salix spp.) bark hot water extracts against coronaviruses and enteroviruses. Willow bark has long been recognized for its medicinal properties and has been used in traditional medicines. However, its potential as a broad-spectrum antiviral agent remains relatively unexplored.

Methods: Cytopathic effect inhibition assay and virucidal and qPCR-based assays were used to evaluate the antiviral potential of the bark extracts. The mechanism of action was investigated using time-of-addition assay, confocal microscopy, TEM, thermal, and binding assays. Extracts were fractionated and screened for their chemical composition using high-resolution LC-MS.

Results: The native Salix samples demonstrated their excellent antiviral potential against the non-enveloped enteroviruses even at room temperature and after 45 s. They were equally effective against the seasonal and pandemic coronaviruses. Confocal microscopy verified the loss of infection capacity by negligible staining of the newly synthesized capsid or spike proteins. Time-of-addition studies demonstrated that Salix bark extract had a direct effect on the virus particles but not through cellular targets. Negative stain TEM and thermal assay showed that antiviral action on enteroviruses was based on the added stability of the virions. In contrast, Salix bark extract caused visible changes in the coronavirus structure, which was demonstrated by the negative stain TEM. However, the binding to the cells was not affected, as verified by the qPCR study. Furthermore, coronavirus accumulated in the cellular endosomes and did not proceed after this stage, based on the confocal studies. None of the tested commercial reference samples, such as salicin, salicylic acid, picein, and triandrin, had any antiviral activity. Fractionation of the extract and subsequent MS analysis revealed that most of the separated fractions were very effective against enteroviruses and contained several different chemical groups such as hydroxycinnamic acid derivatives, flavonoids, and procyanidins.

Conclusion: Salix spp. bark extracts contain several virucidal agents that are likely to act synergistically and directly on the viruses."

Beyond aspirin: Willow bark also found to be a broad-spectrum antiviral (published 11/9/2023)

Willow (Salix spp.) bark hot water extracts inhibit both enveloped and non-enveloped viruses: study on its anti-coronavirus and anti-enterovirus activities (open access, published 11/8/2023)