Virucidal Activity of Lemon Essential Oil against Feline Calicivirus Used as Surrogate for Norovirus

Norovirus (NoV) is regarded as a common cause of acute gastrointestinal illness worldwide in all age groups, with substantial morbidity across health care and community settings. The lack of in vitro cell culture systems for human NoV has prompted the use of cultivatable caliciviruses (such as feline calicivirus, FCV, or murine NoV) as surrogates for in vitro evaluation of antivirals. Essential oils (EOs) may represent a valid tool to counteract viral infections, particularly as food preservatives. In the present study, the virucidal efficacy of lemon EO (LEO) against FCV was assessed in vitro. The gas chromatography hyphenated with mass spectrometry (GC/MS) technique was used to reveal the chemical composition of LEO. The following small molecules were detected as major components of LEO: limonene (53%), beta-pinene (14.5%), gamma-terpinene (5.9%), citral (3.8%), alpha-pinene (2.4%), and beta-thujene (1.94%). LEO at 302.0 mu g/mL, exceeding the maximum non cytotoxic limit, significantly decreased viral titre of 0.75 log(10) TCID50/50 mu L after 8 h. Moreover, virucidal activity was tested using LEO at 3020.00 mu g/mL, determining a reduction of viral titre as high as 1.25 log(10) TCID50/50 mu L after 8 h of time contact. These results open up perspectives for the development of alternative prophylaxis approaches for the control of NoV infection.