Structure and in vitro antiviral activity of triterpenoid saponins from Calendula arvensis

A reinvestigation of the aerial parts of Calendula arvensis afforded, in addition to the oleanolic acid glycosides 1-4 (4), the new glycoside 5 whose structure was elucidated by spectral and chemical studies and determined as 3-O-(beta-D-galactopyranosyl-(1----3) [beta-D-glucopyranosyl-(1----4)]-beta-D-glucopyranosyl) oleanolic acid (28----1)-beta-D-glucopyranosyl ester. Furthermore, some antiviral tests were performed on glycosides 1-5 and on 5a, the hydrolysis product of 5, towards vesicular stomatitis virus (VSV) and rhinovirus (HRV) infection in cell cultures. An inhibitory effect against VSV multiplication was observed for all the compounds tested while HRV replication was significantly affected only by compound 3.