Bioactive A-ring rearranged limonoids from the root barks of Walsura robusta

Abstract Screening active natural products, rapid identification, and accurate isolation are of great important for modern natural lead compounds discovery 1 . We hereby reported the isolation of seven new neotecleanin-type limonoids ( 1 7 ), seven new limonoids with 5-oxatricyclo[5.4.0.1 1. , 4. ]hendecane ring system ( 8 14 ), and two new precursors ( 15 16 ) together with four known limonoids ( 17 20 ) from the root barks of Walsura robusta . Their structures, including their absolute configurations, were elucidated based on analyses of HR-ESI-MS, 1D/2D NMR, ECD spectrum calculations and single-crystal X-ray diffraction techniques. Compounds 2 , 8 , 9 , 11 , 13 , 14 , 18 showed significant anti-inflammatory activities in LPS-induced RAW 264.7 cell line, BV2 microglial cells, and Propionibacterium acnes -stimulated THP-1 human monocytic cells. Walrobsin M ( 11 ) exhibited anti-inflammatory activity with IC 50 value of 7.96±0.36 μmol/L, and down-regulated phosphorylation levels of ERK and p38 in a dose-dependent manner.