Recurrent viral outbreaks have a significant negative impact on society. This creates a need to develop novel strategies to complement existing antiviral approaches. In experiments with cell samples, scientists from the University of Jyväskylä, the Institute of Natural Resources of Finland and the University of Turku investigated the antiviral potential of willow (Salix species) Bark extracts in hot water against coronaviruses and enteroviruses.
Willow bark extracts contain several virucidal agents that probably act synergistically and directly on viruses. Image credit: Mona El Falaky.
The emergence of viral outbreaks leading to epidemics and pandemics causes enormous stress on the global economy and public health.
Antiviral agents, such as vaccines, medications, and virucides, help reduce viral transmission.
Virucides are used to reduce viral load on surfaces and in the environment. They are used as disinfectants for surface sterilization of biological and medicinal products.
Additionally, they have been used to inactivate viruses in foods, detergents and cosmetics.
However, most virucides are chemical disinfectants, which are hazardous in nature and cause environmental pollution. In addition, they cause side effects on human health, such as skin irritation.
Additionally, non-enveloped viruses, such as enteroviruses, are largely resistant to chemical disinfectants.
Although vaccines are an effective weapon against viral infection, it is not feasible to develop a vaccine against all enteroviruses. Additionally, the vaccine development and approval process also takes time.
Currently, there are no clinically approved medications for enteroviruses.
Therefore, there is a great need to find broad-acting antiviral agents that reduce the infectivity of viruses around us and that can complement vaccines and drugs in the fight against viruses.
“We need efficient and broad-based tools to combat the virus load in our daily lives,” he said. Professor Varpu Marjomäkiresearcher at the University of Jyväskylä.
“Vaccines are important, but they cannot address many of the emerging serotypes early enough to be effective on their own.”
In their previous study, Professor Marjomäki and colleagues showed that hot water extracts of willow bark are very effective against non-enveloped enteroviruses (Coxsackie virus A9) and are not cytotoxic at the concentrations used.
Interestingly, none of the reference compounds tested, such as triandrin, salicin, salicylic acid or picein, showed antiviral activity, suggesting that the bioactive properties of willow clone bark extracts could be due to synergistic effects. of different bioactive agents such as tannins and other polyphenols.
In the present study, the antiviral activity of hot water willow bark extracts was tested against HCoV-OC43 and SARS-CoV-2, and its mechanism of action against previously tested coronaviruses and enteroviruses was clarified.
“To make the extract, we harvested commercially grown willow branches,” the researchers said.
“The bark was cut into pieces, frozen, ground and then extracted with hot water.”
The extracts tested by the team showed antiviral potency against both viruses by having a direct effect on the viral particles.
They caused both viruses to cluster, but stopped infection in different ways for enveloped and non-enveloped viruses: through the increased stability of the structure of enteroviruses, but through the compromised structure of coronaviruses.
“The extracts acted through different mechanisms against different viruses,” said Professor Marjomäki.
“But the extracts were equally effective at inhibiting enveloped and non-enveloped viruses.”
The authors also tested existing medical compounds derived from willow bark, as well as commercially prepared salixin extract and salixin powder.
Of these, only the salixin extract showed antiviral activity, suggesting that the success of the scientists’ willow bark extract could be the result of interactions of different bioactive compounds.
More research will be needed to understand the bioactive compounds involved, their chemical structure and how they work, which could lead to revolutionary new antiviral treatments.
“We are currently continuing the fractionation and identification of bioactive molecules from willow bark extracts,” said Professor Marjomäki.
“This will give us a number of identified pure molecules that we can study in more detail.”
“In addition, we will study a larger number of viruses with purified components. “The purified components will provide us with better opportunities to study their mechanisms of action.”
The teams results are published in the magazine Frontiers in microbiology.
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Dhanik Reshamwala et al. 2023. Willow (Salix spp.) Bark extracts in hot water inhibit enveloped and non-enveloped viruses: study on their anticoronavirus and antienterovirus activities. Forehead. microbiol 14; doi:10.3389/fmicb.2023.1249794
