Iridoid glycosides from Eremostachys glabra

Reversed-phase preparative HPLC of a methanol extract of the rhizomes of Eremostachys glabra yielded three new iridoid glycosides, namely, 6,9-epi-8-O-acetylshanziside methyl ester (1), 5,9-epi-penstemoside (2), and 5,9-epi-7,8-didehydropenstemoside (3). Their structures were elucidated on the basis of spectroscopic data interpretation. The free-radical scavenging activity of these compounds was assessed using the DPPH assay.