Bioassay-guided fractionation of Eupatorium Perfoliatum L. towards anti-Influenza A-activity leads to dicaffeoyl quinic acids

Ethanolic extracts from Eupatorium perfoliatum L. (Asteraceae) are traditionally used for fever treatment. Furthermore reports on the use against viral-associated common colds are documented (Contramutan®). An ethanol-water extract (62%) from E. perfoliatum was found to be active in MTT and plaque reduction assay against influenza A virus (IAV) H1N1v 2009 with an IC₅₀ of approx. 55µg/mL due to an inhibition of viral entry. Bioassay-guided fractionation towards the active compounds led to the isolation of active fraction B (IC₅₀ approx. 48µg/mL). Further fractionation of B into EtOAc- and MeOH-soluble subfractions yielded 2 antiviral multicomponent fractions C and D, resp. The antiviral activity found in the ethanolic extract was due to compounds interacting with polyvinylpyrrolidone (PVP). Treatment of fraction D with PVP and subsequent LC-MS studies revealed a drastic reduction of peaks, which should hence comprise the antiviral compound. The respective peaks were assigned to dicaffeoyl quinic acids and flavonole glycosides. Isolation and in vitro testing of these compounds to verify this result towards the development of a new class of antiviral compounds leads to 3 yet unidentified dicaffeoyl quinic acids. Summarizing, the traditional use of extracts from E. perfoliatum against viral respiratory diseases seems to be justified, due to the presence of polyphenolic components with antiviral activity.