Structure and in vitro antiviral activity of sesquiterpene glycosides from Calendula arvensis

Previous research on the aerial parts of Calendula arvensis led to the isolation of the epicubebol glycoside 1 and of the sesquiterpene glycosides 2-5 based on the alloaromadendrane skeleton. A further investigation has revealed two new glycosides, 6 and 7, derived from the same sesquiterpene, the structures of which were elucidated by spectral studies. Furthermore a series of antiviral tests has been performed on glycosides 1-7 by examining their ability to interfere with rhinovirus 1B and vesicular stomatitis virus infection in vitro. Only glycoside 1 slightly reduced rhinovirus multiplication. All the compounds were able to inhibit vesicular stomatitis virus infection, 1 and 2 being the most effective.