Iridoid glycosides from Phlomis likiangensis with free -radical scavenging activity

Phytochemical investigation of an extract of the aerial and underground parts of Phlomis likiangensis resulted in the identification of five new iridoid glycosides, namely as 5,9-epi-6-methoxy-7,8-dehydropenstemonoside (1), 6-methoxy-7,8-dehydropenstemonoside (2), 6-methoxy-7,8-dehydropenstemoside (3), 6-ethoxy-7,8-dehydropenstemoside (4), and phloloside G (5). On the basis of a combination of spectroscopic data and acid hydrolysis, their structures were determined. The free-radical scavenging activity of these compounds was assessed using the DPPH and ABTS assays. (C) 2017 Elsevier Ltd. All rights reserved.