Abstract
Hydroalcoholic extracts and pressed juice from Echinacea pallida were phytochemically characterised by HPLC-MS analyses. Ferulic and caffeic acid derivatives were identified as major constituents. All tested extracts and pressed juice from Echinacea pallida exhibited a low cytotoxic activity on monkey kidney cells in vitro. The inhibitory activity of Echinacea against herpes simplex virus types 1 and 2 (HSV-1, HSV-2) was analysed with plaque reduction assays. All hydroalcoholic extracts exhibited high levels of antiviral activity against both types of herpesvirus in a dose-dependent manner. Plaque formation was significantly reduced by more than 99 % or completely absent. Pressed juice from E. pallida revealed the highest antiviral activity against HSV-1 and HSV-2 when compared to hydroalcoholic Echinacea extracts and even highly diluted Echinacea pressed juice still inhibited viral infectivity. Hydroalcoholic extracts were quite active against herpetic infection when HSV-1 or HSV-2 were pretreated with the extracts. In contrast, Echinacea pressed juice revealed antiviral activity during all phases of the viral replication cycle. Additionally, Echinacea pressed juice demonstrated protection of cells against viral infection. In conclusion, hydroalcoholic E. pallida extracts interfere with free herpesvirus but pressed juice is able to interact with herpesvirus inside and outside the cell as well as to protect cells against viral infection, probably by interfering with virus attachment. Hydroalcoholic extracts and pressed juice from E. pallida demonstrated high selectivity indices, a necessary prerequisite for a potential topical treatment of herpetic infections. Different types of Echinacea preparations, such as commercial tinctures, tablets, and teas, are expected to offer different antiviral profiles.
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