Mexican oregano (Lippia graveolens) is a plant found in Mexico and Central America that is traditionally used as a medicinal herb. In the present study, we investigated the antiviral activity of the essential oil of Mexican oregano and its major component, carvacrol, against different human and animal viruses. The MTT test (3-4,5-dimethythiazol-2yl)-2,5-diphenyl tetrazolium bromide) was conducted to determine the selectivity index (SI) of the essential oil, which was equal to 13.1, 7.4, 10.8, 9.7, and 7.2 for acyclovir-resistant herpes simplex virus type 1 (ACVR-HHV-1), acyclovir-sensitive HHV-1, human respiratory syncytial virus (HRSV), bovine herpesvirus type 2 (BoHV-2), and bovine viral diarrhoea virus (BVDV), respectively. The human rotavirus (RV) and BoHV-1 and 5 were not inhibited by the essential oil. Carvacrol alone exhibited high antiviral activity against RV with a SI of 33, but it was less efficient than the oil for the other viruses. Thus, Mexican oregano oil and its main component, carvacrol, are able to inhibit different human and animal viruses in vitro. Specifically, the antiviral effects of Mexican oregano oil on ACVR-HHV-1 and HRSV and of carvacrol on RV justify more detailed studies.

Dentre as propriedades biológicas da própolis, a atividade antimicrobiana tem merecido destacada atenção. Neste artigo, descreve-se a atividade antiviral de dois extratos etanólicos de própolis (EP1 e EP2) frente aos vírus: calicivírus felino (FCV), adenovírus canino tipo 2 (CAV-2) e vírus da diarréia viral bovina (BVDV). Um dos extratos (EP1) foi obtido por extração etanólica de própolis obtida da região central do Estado do Rio Grande do Sul e o segundo (EP2), obtido comercialmente de uma empresa de Minas Gerais. A análise dos extratos de própolis através da cromatografia líquida de alta eficiência (CLAE) identificou a presença de flavonóides como: rutina, quercetina e ácido gálico. A atividade antiviral bem como a citotoxicidade dos extratos aos cultivos celulares foram avaliadas através do MTT [3- (4,5 dimetiltiazol-2yl)-2-5-difenil-2H tetrazolato de bromo]. Ambos os extratos evidenciaram atividade antiviral frente ao BVDV e CAV-2 quando acrescidos ao cultivo celular anteriormente à inoculação viral. Os extratos foram menos efetivos contra o FCV em comparação aos resultados obtidos com os outros vírus, e a atividade antiviral neste caso foi observada apenas quando a própolis estava presente após a inoculação viral. O extrato obtido no laboratório (EP1) apresentou valores mais altos de índice de seletividade (IS=CC50/ CE50), quando comparado à outra amostra (EP2). Em resumo, a própolis apresentou atividade antiviral frente a três diferentes vírus, o que a torna alvo para o desenvolvimento de novos compostos naturais com atividade antiviral.

Propolis is a resinous substance produced by bees for which several biological activities have been attributed. In this article, the antiviral activity of two propolis extracts was tested against bovine viral diarrhea virus (BVDV), canine adenovirus type 2 (CAV-2), and feline calicivirus (FCV). One of the extracts was obtained by ethanolic extraction of propolis from the Santa Maria (RS) region, while the other was bought from a Minas Gerais industry. The high efficiency liquid cromatography (HPLC) analysis detected the presence of some flavonoids like rutin, quercetin, and gallic acid. The MTT test was applied in order to detect the citotoxicity and also the antiviral activity. Both extracts showed antiviral activity against BVDV and CAV-2 when incubated with the cell cultures before viral inoculation. The extracts were less effective against FCV comparing to the results for the other viruses and, the antiviral activity was observed only when the própolis was present after virus inoculation The extract obtained in the lab showed the highest selectivity index (SI= CC50/ EC50). Thus, propolis showed antiviral activity against three different viruses, making it a target for the development of new natural compounds with antiviral activity.