The Flavonoid Fraction from Rhoeo discolor Leaves Acting as Antiviral Against Influenza A Virus

In vitro antiviral effect of a crude methanol extract and six fractions isolated from Rhoeo discolor against pandemic influenza A (H1N1) was evaluated in this study. The phytochemical analysis to identify the main classes of secondary metabolites was performed by thin layer chromatography (TLC). The cytotoxic effect and cell viability was determined in MDCK cells, and the antiviral activity was evaluated by qRT-PCR to detect influenza virus nucleoprotein (NP) gene. Finally a metabolomic analysis was performed using UPLC-MS. The phytochemical analysis revealed the presence of coumarins, tannins, saponins and flavonoids in the methanol extracts. Cytotoxicity related to 50% cell viability indicated concentrations of <1 mu g/mL for the six fractions tested and >1 mu g/mL for the crude extracts. Fraction MF1 inhibited synthesis of viral NP at co-treatment level at a concentration of 0.30 +/- 0.02 g/mL with a selectivity index (SI) of 30. The metabolomic analysis identified the presence of five flavonoids kaempferol, quercetin, isoquercetin luteolin-5-glucoside and rutin. Antiviral activity of flavonoids from R. discolor against the influenza A (H1N1) virus are reported for the first time.