Syringenes A–L: Bioactive dimeric eremophilane sesquiterpenoids from Syringa pinnatifolia

•Eleven new and one known dimeric eremophilane sesquiterpenoids with unusual skeleton were isolated from Syringa pinnatifolia stems guided by 1H NMR and LC-MS data.•Biological assays of anti-inflammation and cytotoxicity against HepG2 cells of these compounds were evaluated.•5 and 6 significantly induced apoptosis via activation of ERK.•Molecular docking studies revealed that the carbonyl and hydroxyl groups at C-11/C-6′ of bioactive compounds bind to the ERK.