Iridoid Glucosides and p-Coumaroyl Iridoids from Viburnum luzonicum and Their Cytotoxicity

Four new iridoids glucosides (1-4) and seven new iridoid aglycons (5-11) bearing (E)- or (Z)-p-coumaroyl groups were isolated from a methanol extract of the dried leaves of Viburnum luzonicum collected in Kaoshiung, Taiwan. The structures of the new compounds, named luzonoside A (1), luzonoside B (2), luzonoside C (3), luzonoside D (4), luzonoid A (5), luzonoid B (6), luzonoid C (7), luzonoid D (8), luzonoid E (9), luzonoid F (10), and luzonoid G (11), were elucidated by analysis of spectroscopic data and comparison with values for previously known analogues. Among the iridoids isolated in the present study, glucosides 1 and 2, and their aglycons 5-9, exhibited moderate inhibitory activity against HeLa S3 cancer cells, whereas 3 and 4 showed no cytotoxicity even at 100 microM.