title: Antiviral activity of baicalein and quercetin against the Japanese encephalitis virus.
abstract: Japanese encephalitis (JE), a mosquito-borne viral disease, is endemic to the entire east and southeast Asia, and some other parts of the world. Currently, there is no effective therapeutic available for JE; therefore, finding the effective antiviral agent against JEV replication is crucial. In the present study, the in vitro antiviral activity of baicalein and quercetin, two purportedly antiviral bioflavonoids, was evaluated against Japanese encephalitis virus (JEV) replication in Vero cells. Anti-JEV activities of these compounds were examined on different stages of JEV replication cycle. The effects of the compounds on virus replication were determined by foci forming unit reduction assay (FFURA) and quantitative RT-PCR. Baicalein showed potent antiviral activity with IC(50) = 14.28 µg/mL when it was introduced to the Vero cells after adsorption of JEV. Quercetin exhibited weak anti-JEV effects with IC(50) = 212.1 µg/mL when the JEV infected cells were treated with the compound after virus adsorption. However, baicalein exhibited significant effect against JEV adsorption with IC(50) = 7.27 µg/mL while quercetin did not show any  anti-adsorption activity. Baicalein also exhibited direct extracellular virucidal activity on JEV with IC(50) = 3.44 µg/mL. However, results of quantitative RT-PCR experiments confirmed the findings from FFURA. This study demonstrated that baicalein should be considered as an appropriate candidate for further investigations, such as the study of molecular and cellular mechanism(s) of action and in vivo evaluation for the development of an effective antiviral compound against Japanese encephalitis virus.
authors.affiliation: Tropical Infectious Disease Research and Education Center (TIDREC), Department of Medical Microbiology, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia. keivan@um.edu.my.
authors.forename: Jefree
authors.initials: J
authors.lastname: Johari
authors.forename: Aynaz
authors.initials: A
authors.lastname: Kianmehr
authors.forename: Mohd Rais
authors.initials: MR
authors.lastname: Mustafa
authors.forename: Sazaly
authors.initials: S
authors.lastname: Abubakar
authors.forename: Keivan
authors.initials: K
authors.lastname: Zandi
mesh_terms: D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D018890:Chemoprevention; D002522:Chlorocebus aethiops; D004664:Encephalitis Virus, Japanese / Q000187:drug effects* / Q000502:physiology; D004672:Encephalitis, Japanese / Q000517:prevention & control / Q000821:virology; D044950:Flavanones / Q000494:pharmacology*; D011794:Quercetin / Q000494:pharmacology*; D014709:Vero Cells; D053586:Virus Internalization / Q000187:drug effects; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000998:Antiviral Agents; D044950:Flavanones; C006680:baicalein; D011794:Quercetin