Rhododendrin, an analgesic/anti-inflammatory arylbutanoid glycoside, from the leaves of Rhododendron aureum

To identify an analgesic/anti-inflammatory component from the leaves of Rhododendron aureum (Ericaceae), phytochemical isolation and pharmacological assays (writhing assays and vascular permeability assay for analgesic action in mice; carrageenan-induced paw edemaand TPA-induced ear edema assays of anti-inflammatory action in rats) were performed. Four compounds were isolated from the active fraction (BuOH fraction) by silica gel column chromatography and identified as (−)-rhododendrol, (−)-rhododendrin, avicularin and hyperoside by spectroscopic methods. Rhododendrin, the main compound of the BuOH fraction, exhibited significant analgesic actions in mice and anti-inflammatory actions in rats. This compound accounted for 3.1% of the MeOH extract and 0.48% of dried leaves, respectively, on HPLC analysis. These results suggest that rhododendrin is the major biologically active substance in the leaves of R. aureum with analgesic/anti-inflammatory activity.