Secoiridoid glucosides and related compounds from Syringa reticulata and their antioxidant activities

A 70% EtOH extract from the bark of Syringareticulata has shown significant antioxidant activity. Chemical study on the extract resulted in the isolation of seventeen compounds (1-17), including a novel oleoside-type secoiridoid glucoside, reticuloside (1), and the structures were elucidated on the basis of extensive spectroscopic analyses. Among the isolated compounds, jaspolyoside (2), oleuropein (4) and 2-(3,4-dihydroxy)-phenylethyl-β-d-glucopyranoside (17), showed the most potent superoxide anion scavenging activity with the EC(50) values of 4.97, 2.57 and 4.97μM, respectively. The structure-activity relationship indicated that the presence of 2-(3,4-dihydroxyphenyl)-ethoxy group is important for exhibiting the activity.