Trimeric and dimeric sesquiterpenoids from Artemisia atrovirens and their cytotoxicities

Two sesquiterpenoid trimers, artematrotrimers A (1) and B (2), and two sesquiterpenoid dimers, artematrodimers A (3) and B (4), possessing unprecedented scaffolds with a methylene-bridged connection were identified from Artemisia atrovirens. Their structures and absolute stereochemistry were determined by comprehensive spectroscopic data, single-crystal X-ray diffraction analyses, and ECD calculations. Compounds 1–4 represent a new type of sesquiterpenoid oligomers featuring the connections between hetero sesquiterpenoid units via one or two C–C bonds. A possible biosynthetic pathway for 1–4 was also proposed. Compound 3 showed obvious cytotoxicity against HepG2 and Huh7 cell lines with IC50 values of 21.9 and 22.6 μM, respectively.