COVID-19 Disinfectants: Researchers From Queen’s University-Belfast Say That Rosin Soap Could Serve As A Virucide Against The SARS-CoV-2 Virus
A new study by researchers from Queen’s University Belfast-UK has found that rosin soap could serve as a virucide against the SARS-CoV-2 coronavirus. The study findings showed that rosin soap was able to rapidly and potently inactivate influenza virus and other enveloped viruses.
The study team which also included researchers from Finland showed that rosin soap
can inactivate the human enveloped viruses such as the influenza A virus (IAV), respiratory syncytial virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
For IAV, rosin soap could provide a 100,000-fold reduction in infectivity. However, Rosin soap failed to affect the non-enveloped encephalomyocarditis virus (EMCV). The inhibitory effect of Rosin soap against IAV infectivity was dependent on its concentration but not dependent on incubation time nor temperature. The study team demonstrated a novel chemical inactivation method against enveloped viruses, which could be of use in preventing virus infections in certain settings.
The study findings were published on a preprint server and are currently being peer reviewed. https://www.biorxiv.org/content/10.1101/2021.07.19.452918v1
Typically viruses remain a significant cause of human disease and death, most notably illustrated through the current Covid-19 pandemic. Control of virus infection continues to pose a significant global health challenge to the human population. Viruses can spread through multiple routes, including via environmental and surface contamination where viruses can remain infectious for days. Methods to inactivate viruses on such surfaces may help mitigate infection.
Moreover with studies showing that the SARS-CoV-2 virus can remain for long on certain types of human skin and also certain viral proteins have the potential to interact with human skin, a virucidal soap included in our daily bath regimens might also be useful. https://www.thailandmedical.news/news/breaking-study-finds-high-expression-of-ace2-receptors-on-keratinocytes-and-warns-that-human-skin-could-be-a-potential-target-for-sars-cov-2
Rosin is a solid resin produced from Tall oil obtained from coniferous trees such as pine trees and are used for various applications, including as a soap.
The resin rosin contains numerous lipid-soluble acids and has previously demonstrated antibacterial activity against Gram-positive bacteria, in particular, acting by disruption of the cell membrane.
The study findings highlighted the potential of rosin soap as a virucide and showed a ten-thousand-fold drop in infectivity against enveloped viruses such as influenza and SARS-CoV-2 in particular.
For the study, the research team infected Vero cells with influenza A virus, respiratory syncytial virus (RSV), SARS-CoV-2, or encephalomyocarditis virus (EMCV), Madin-Darby canine kidney (MDCK) cells with influenza A, and HEp-2 cells with RSV, subsequently exposing each to rosin solution at concentrations of 0.025%-2.5% for 5-30 minutes.
Importantly the cytopathic effect of infection was also assessed 72 hours post-treatment, as the severity of infection can be inferred from the degree of cell rounding and death observed, especially in influenza-sensitive cell lines such as Madin-Darby Canine Kidney (MDCK).
Interestingly the acids of the rosin soap were only found to be cytotoxic to MDCK cells at the highest concentration tested, though the efficacy of virus inactivation against influenza was higher.
In order to test the potential of rosin as a surface disinfectant, not intended to be applied directly to the hands, rosin soap at 2.5% concentration was exposed to the virus for five minutes before filtration and purification of the virus and subsequent exposure to cells.
The virus was effectively inactivated, showing almost no infectivity towards the cells, while no residual cytotoxicity was observed towards the cells following the purification process.
The EMCV is a model non-enveloped virus often used in biomedical research.
However in identical experiments to the above virus, infectivity was not reduced by exposure to rosin soap. At the same time, it was observed that each of the enveloped viruses was affected by the soap in a concentration-dependent manner. Incubation time with the soap did not notably influence the virucidal rate.
There was little observed difference in infectivity amongst any of the enveloped viruses, whether exposed for five or thirty minutes. Similarly, incubation temperature with rosin had little influence on the efficacy of the soap as an antiviral, whether kept at 37⁰C, 20⁰C, or 4⁰C.
It is already known that many human pathogenic viruses can persist on surfaces for long periods of time, providing the opportunity for direct transmission to numerous individuals.
The current SARS-CoV-2 pandemic has led to the urgent search for safe, cheap, and environmentally friendly surface cleaners and personal soaps that are suitable for repeated use throughout the day.
The study findings suggest that rosin soap could be one solution.
From the study observations, as the soap was ineffective against non-enveloped viruses, it likely has a mechanism of action based on disruption of the lipid membrane, similar as against Gram-positive bacteria.
The study team however suggests that other non-enveloped viruses such as norovirus could be tested to determine if there is any effect. The precise active compound, if such a single compound exists, within rosin soap that exerts membrane-disrupting activity against viruses has not been identified.
The team suspects that virucidal effect could be caused adjusted surface tensions by surfactants in rosin soap.
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