Four New Acylated Iridoid Glycosides from the Aerial Part of Veronicastrum sibiricum and Their Antioxidant Response Element-Inducing Activity

Four new (1 - 4) and one known (5) acylated iridoid glycosides were isolated from the aerial parts of Veronicastrum sibiricum (L.) Pennell. The chemical structures of the isolated compounds were determined to be 3,4-dicinnamoyl-6-O-rhamnopyranosyl-10-O-bergaptol-5,7-bisdeoxycynanchoside (1), 3,4-dicinnamoyl-6-O-rhamnopyranosylpaulownioside (2), 2,4-dicinnamoyl-6-O-rhamnopyranosylcatalpol (3), 3,4-dicinnamoyl-6-O-rhamnopyranosylaucubin (4), and 3,4-dicinnamoyl-6-O-rhamnopyranosylcatalpol (5) using spectroscopic techniques. Among these compounds, compound 5 increased antioxidant response element (ARE) luciferase activity.