Atividade antiviral de óleos essenciais e monoterpenos contra vírus de bovinos e felinos como potenciais modelos para vírus humanos

Abstract

The essential oils obtained from plants used as condiments are an important source of compounds with pharmacologic activity. In the present study, the antiviral activity of the essential oil of Ocimum basilicum L. (basil) and from the monoterpens camphor, 1,8-cineol and timol was tested against the bovine viral diarrhea virus (BVDV), while the essential oil of Rosmarinus officinalis L. (rosemary), Lippia graveolens HBK. (mexican oregano) and Thymus vulgaris L. (thyme) were tested against the feline calicivirus (FCV). The colorimetric test MTT ([3- (4.5-dimetilazol-2-il)-2.5-brometo of difeniltetrazolium]) was applied for the measurement of cytotoxicity, and the antiviral tests were performed by the plaque reduction assay. Three different protocols were applied: a) the virus was incubated with the essential oils or compounds before the inoculation into cells (virucidal assay); b) the cells were treated with the essential oils or compounds prior to virus inoculation; or, c) essential oils and compounds were added to the cells after virus inoculation and maintained for 72 hours. The results were expressed as CC50 (cytotoxic concentration to 50% of the cell culture), IC50 (inhibitory concentration to 50%) and SI (selectivity index = CC50/IC50). The best results were evidenced for the monoterpens camphor (SI=13.88) and the 1,8-cineol (IS=9.05) against BVDV. These results were obtained from the virucidal protocol and these compounds showed also the lower toxicicity towards the bovine kidney cells culture (Madin-Darby bovine kidney cells = MDBK) (CC50 = 4420.12 μg/mL and 2996.10 μg/mL, respectively). Regarding to the tests with FCV, the thyme essential oil showed the best results with SI=8.57 for c treatment. The basil essential oil had a moderate action in the a protocol (SI=6.54) and also for the c protocol (SI=6.86). In addition, the basil essential oil exhibited low levels of cytotoxicity towards the Crandel-Reese feline kidney cells (CRFK), with CC50 of 1300.21 μg/mL. In conclusion, the essential oils and monoterpens examined showed different levels of inhibitory activity on diverse moments of the viral infection. The antiviral activity demonstrated by the essential oils and compounds on BVDV and FCV may suggest a possible action on the hepatitis C virus (HCV) and norovirus (NoVs), respectively; since BVDV ande FCV shows several structural and replicative similarities to HCV and NoVs.