The Antiviral Properties of Different Woods

During the pandemic, many of us upped our cleaning regimes, hoping that disinfectants would neutralize the virus on surfaces and touch points. But repeated heavy use of such products poses environmental and health concerns. Additionally, some viruses can endure for weeks and are often able to resist standard disinfection techniques. But could there be a more natural solution?

In our deeply connected world, containing viral outbreaks is a big challenge. SARS and COVID-19 have shown us that viruses can spread quickly across continents and borders, both through direct human contact but also via contaminated surfaces.¹ Viruses do not replicate outside their host but they can persist for a long time on different surfaces.² Many of us rely on disinfectants to maintain hygienic touch points in our homes and work spaces, but some viruses have a strong protein capsid which is not always broken down by these products.³

This has translated into renewed interest in antiviral surfaces, and the role they could play in reducing circulating viral load. Wood is naturally antimicrobial,⁴ and as such has traditionally been used for wine production and cheese boards. It is thought the underlying mechanism arises from a variety of natural bioactive plant compounds, as well as the hygroscopic nature—which promotes rapid drying—but there is a complex interplay of factors to unpick.

Now, new work published in ACS Applied Materials & Interfaces explores the antiviral efficacy of various woods against enveloped coronaviruses and nonenveloped enteroviruses.⁵ To determine viral activity, a team of researchers in Finland conducted a direct flushing experiment to measure how much of the virus was absorbed by the wood surfaces. This involved applying virus droplets to the surfaces, incubating them under high humidity, and then washing the surfaces to collect the virus for analysis. Six different wood species were tested, as well as samples of varying smoothness, a wood-plastic composite, and a polyethylene plastic control.

The team found that coniferous woods such as Scots pine and Norway spruce revealed excellent antiviral activity within as little as 10 minutes—particularly against enveloped viruses. In contrast, deciduous hardwoods displayed varied efficacy, although oak worked well against the enterovirus. The antiviral activity appeared consistent across a range of humidities, but the antiviral effect was typically quicker at warmer temperatures. When they examined the chemical composition, the team found resin acids and terpenes in the pine and spruce, and a high phenolic content in oak. Crucially, the wood worked best against the viruses when it had not been thermally treated or mixed with plastic in a composite form.

The study highlights the role of bioactive chemicals in wood’s natural antimicrobial effects, and the results could help to open new avenues for building natural and sustainable surfaces into our homes and public spaces. This builds upon previous work from 2021 that looked at ways to convert woody biomass into antiviral substances. The paper, published in ACS Sustainable Chemistry & Engineering, details how beech wood was decomposed and put through silica gel chromatography, with the resulting fractions exhibiting strong antiviral activity against the encephalomyocarditis virus (EMCV) without cytotoxicity.⁶ Structural analyses revealed the separated antiviral substances to be lignin–carbohydrate complexes, and further tests showed that breaking the carbohydrate part of these complexes significantly reduced their ability to fight the virus—suggesting the carbohydrate portion was playing a critical role in the inactivation of EMCV, with similar results seen with pyroligneous acids from hardwood, softwood, and bamboo.⁷ Other work has identified lignin as a sustainable antiviral coating that can inactivate the herpes simplex virus.⁸ Furthermore, this coating was stable in ambient conditions, with no decrease in antiviral activity over six months.

Better understanding the bioactive compounds in different types of wood should help to develop modern and sustainable approaches to deal with viral transmission. Additionally, existing work to identify the core substances suggest there is a role for waste biomass as well as solid wooden surfaces that retain their natural structure—making this an extremely attractive and environmentally friendly strategy in the ongoing fight against viruses.

References

1. COVID-19: Challenges, Progress and Future Implications. ACS Journals Virtual Collection 2021-2022.
2. Firquet, S. et al. Survival of Enveloped and Non-Enveloped Viruses on Inanimate Surfaces. Microbes Environ 2015, 30 (2), 140–144.
3. Wood, A. and Payne, D. The Action of Three Antiseptics/Disinfectants against Enveloped and Non-Enveloped Viruses. J. Hosp Infect 1998, 38 (4), 283–295.
4. Aviat, F. et al. Microbial Safety of Wood in Contact with Food: A Review. Comprehensive Reviews in Food Science and Food Safety 2016, 15 (3), 491–505.
5. Shroff, S. et al. Tree Species-Dependent Inactivation of Coronaviruses and Enteroviruses on Solid Wood Surfaces. ACS Appl. Mater. Interfaces 2024, 16, 23, 29621–29633.
6. Li, R. et al. Conversion of Beech Wood into Antiviral Lignin–Carbohydrate Complexes by Microwave Acidolysis. ACS Sustainable Chem. Eng. 2021, 9, 28, 9248–9256.
7. Li, R. et al. Antiviral Activity of Phenolic Derivatives in Pyroligneous Acid from Hardwood, Softwood, and Bamboo. ACS Sustainable Chem. Eng. 2018, 6, 1, 119–126.
8. Boarino, A. et al. Lignin: A Sustainable Antiviral Coating Material. ACS Sustainable Chem. Eng. 2022, 10, 42, 14001–14010.