Virucidal Efficacy of Organic Acids and Plant Essential Oils

Currently, the predominant commercially available disinfectants and sanitizers are formulated with active ingredients including alcohol, halogenated compounds (e.g., sodium hypochlorite), surfactants, oxidizing agents (eg., hydrogen peroxide), and quaternary ammonium compounds. Natural products represent an alternative since they are often effective microbicides and are generally recognized as safe (GRAS) due to their long history of use. The purpose of this study was to evaluate the efficacy of several organic acids and plant essential oils against three bacteriophages (MS2, ΦX174, PR772) with different genome characteristics (e.g., RNA versus DNA, single-stranded versus double-stranded) and against an enveloped and non-enveloped mammalian virus (human coronavirus 229E and feline calicivirus, respectively). The active components of essential oils (carvacrol, cinnamaldehyde, eugenol, thymol) and organic acids (acetic, salicylic, tartaric) demonstrated virucidal activity against the three bacteriophages (typically 1.00 log₁₀ to > 5.00 log₁₀ reductions within 10 min); however, ΦX174 exhibited lesser susceptibility (< 1.0 log₁₀ reduction with all but salicylic acid) and PR772 was the most resistant to cinnamaldehyde. It is unclear why ΦX174, a ssDNA virus, was more resistant to these antimicrobials than the ssRNA (MS2) and dsDNA (PR772) viruses. Carvacrol, eugenol, and thymol were also highly effective against both mammalian viruses (≥ 1.49 and > 3.00 log₁₀ reductions within one and 10 min, respectively). Salicylic acid was the most effective antimicrobial tested with > 3.84 log₁₀ reductions observed with all the viruses in one minute. Based on these results, several of the organic acids and essential oil components included appear to be viable eco-friendly alternatives to currently used disinfectants/sanitizers that are effective against viruses possessing diverse genomic and morphological characteristics.