key: cord-0324222-o64wp6wl
authors: Bell, Stephen H; Fairley, Derek J; Kettunen, Hannele; Vuorenmaa, Juhani; Orte, Juha; Bamford, Connor G G; McGrath, John W
title: Rosin Soap Exhibits Virucidal Activity
date: 2021-07-19
journal: bioRxiv
DOI: 10.1101/2021.07.19.452918
sha: 3b79b026397740517096a323fa65af5e3ca2146b
doc_id: 324222
cord_uid: o64wp6wl

Chemical methods of virus inactivation are used routinely to prevent viral transmission in both a personal hygiene capacity but also in at-risk environments like hospitals. Several ‘virucidal’ products exist, including hand soaps, gels and surface disinfectants. Resin acids, which can be derived from Tall oil produced from trees, have been shown to exhibit anti-bacterial activity. However, whether these products or their derivatives have virucidal activity is unknown. Here, we assessed the capacity of Rosin soap to inactivate a panel of pathogenic mammalian viruses in vitro. We show that Rosin soap can inactivate the human enveloped viruses: 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. Together, we demonstrate a novel chemical inactivation method against enveloped viruses, which could be of use in preventing virus infections in certain settings. Importance 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. Here we present evidence identifying a novel ‘virucidal’ product in Rosin soap, which is produced from Tall oil from coniferous trees. Rosin soap was able to rapidly and potently inactivate influenza virus and other enveloped viruses.

The Rosin soap was produced from crude Tall Oil by Forchem Ltd (Rauma, Finland). 120

It was a water solution obtained from dried Rosin salt consisting less than 10% 121 sodium salts of Tall Oil fatty acids and over 90% sodium salts of resin acids. The 122 resin acids and fatty acids of the product originated from the coniferous trees Pinus 123 sylvestris L. and Picea abies L. The most abundant resin acid types include abietic 124 acid, dehydroabietic acid, pimaric acid and palustris acid. 125 126

Virus inactivation assays were carried out in 96 well plates. Initially complete DMEM 128 (100 μl) was added to each well, except the first column, which was used to 129 initial experiments, incubation of IAV with Rosin Soap Powder gave at least a ten-171 thousand-fold reduction in infectivity (Fig 1) . 172 nor IAV (Fig 2) . In all cases, treatment with Rosin Soap brought infectivity down to 212 baseline and fold inactivation was thus highly dependent on the starting 213 concentration (e.g. greatest for Udorn and lowest for SARS-CoV-2). However, 214 essentially all infectivity was brought to below the limit of detection, which is highly reduction in inhibition observed for each reduction in concentration (Fig 3A) . In 245 contrast to concentration, virucidal activity was independent of incubation 246 temperature (4, room temperature [RT] or 37 o C) and incubation time with there 247 being little difference between a 5-minute incubation compared to a 30-minute 248 incubation (Fig 3A-C) . These data demonstrate the rapid and efficacious activity of and/or through environment contamination (Marquès et al., 2020) . Strategies to 267 eliminate such infectivity from such inanimate and animate surfaces is required. 268

Exporation of strategies that are of natural origin are warranted. To this end we 269 sought to investigate whether Rosin soap has antiviral activity due to its reported 270 antibacterial activity (Söderberg et al., 1990) . Our work presented here shows that 271

Rosin soap also exhibited rapid and potent viricidal activity against pathogenic to determine this. Precisely how Rosin soap impacts the viral envelope is not known 297 at this stage. Rosin soap is a mix of products, and that it would be useful to look at 298 the individual compounds -both in terms of the resin acids and the carboxylic acids. 299

However, there is limited commercial availability of these, and they also have limited 300 solubility in pure solution. As has been done for other virucidal products (Fletcher et 301 al., 2020). 302 303 Unfortunately, due to the cytotoxic nature of Rosin soap at high concentrations (from 304 0.25% to ~0.0025%) in our in vitro cell line cell culture conditions, we were not able 305 to completely negate this background toxicity in our virus infectivity assays (which 306 rely upon cellular integrity) even following purification of our virus/soap mixes by 307 filtration. However, our data suggest that it is highly likely that Rosin soap inactivates 308 the vast majority of infectious particles in a given prep. Using IAV, which grows to 309 very high titres, we were able to demonstrate nearly complete inactivation. It is worth 310 noting that this level of virus titre used in these experiments is higher than likely 311 present in most 'real world' scenarios/environments (Boone and Gerba 2007). In conclusion, we demonstrate the virucidal activity of rosin soap against multiple 327 pathogenic human enveloped viruses. 328

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