Studies on Quercus lusitanica Extracts on DENV-2 Replication

This study aimed to search for compounds with potential inhibitory activities towards DENV-2 replication. In vitro inhibitory activities of plant extracts towards DENV-2 replication were studied and the proteomics profile of cells infected with dengue virus, followed by treatment with plant extracts, were mapped out. Methanol crude and fractionated extracts of Quercus lusitanica were tested. The cytotoxicity of these plant extracts was evaluated by determining the maximum non-toxic dose (MNTD) on C6/36 cells. Antiviral activity was estimated by the reduction of the cytopathic effect (CPE) of DENV-2 in C6/36 cells and by the reduction of virus titre. The crude methanol extracts of Q. lusitanica at the concentration of 180 μg/ml was found to completely inhibit the dengue virus infection at TCID 50 of 1-1000 by the absence of CPE. Protease inhibition assay of the crude and fractionated methanol extracts indicated more than 90% inhibition at the concentration of 0.2 mg/ml of the extracts. Methyl gallate purified from fractionated crude extracts of Q. lusitanica at the MNTD of 100 μg/mL showed a 96% inhibition at TCID 50 of 1000. DENV-2 virus protease inhibition assay of methyl gallate showed more than 98% inhibition at 0.3 mg/mL. Two-dimensional electrophoresis gels of normal, infected and treated cells showed that the treatment with crude methanol extracts as well as methyl gallate purified from the extract down-regulated the expression of the NS1 protein.