Triterpenoids from the roots of Sanguisorba officinalis and their Nrf2 stimulation activity

Abstract

Thirteen undescribed ursane-type triterpenoids, named as sangosides A–M (1–13), including two nor-ursanes, one split ring-ursane and ten ursanes, along with thirty-six known triterpenoids (14–49) were isolated and identified from the roots of Sanguisorba officinalis (Rosaceae). Their structures and absolute configurations were elucidated through spectroscopic data, single-crystal X-ray crystallography and electronic circular dichroism analysis. Their Nrf2 activation activity was evaluated in 293 T cells in vitro. Compounds 2, 5–7, 9–13, 19, 25, 26, 28–39, 41 and 46 showed significant Nrf2 agonistic effects compared with the control group at 25 μM, their cytotoxicity and dose-effect relationship were further studied in a dose-dependent manner. Their structure–activity relationships analysis suggested that the pentacyclic triterpenoids (10, 11, 30–34 and 41) contains two pairs of double bonds on the C & E rings and the ursane-type triterpenoids (25 and 26) with a carbonyl to C-2 and a hydroxyl group at C-3 all showed a considerably Nrf2 activation activity. These results suggested that S. officinalis was worthy of further investigation to find small molecule Nrf2 activators and facilitate their utilization as natural antioxidants.