Novel phthalide dimers from the aerial parts of Ligusticum sinense Oliv cv. Chaxiong

Five new phthalide dimers, chaxiongnolides C–G (1–5), the two enantiomers of riligustilide (6a and 6b) and tokinolide B (7) were isolated from the aerial parts of Ligusticum sinense Oliv cv. Chaxiong. The structures of 1–5 were elucidated through extensive spectroscopic analysis, and the relative configurations of compounds 2 and 3 were further confirmed by an X-ray diffraction experiment. The absolute configurations of 1–3 were assigned by comparing calculated and experimental ECD spectra. The ECD exciton chirality method was used to confirm the absolute configurations of compounds 4, 5, 6a and 6b. Compounds 1–3 are the first dimeric phthalides to be reported that are comprising a sedanolide unit. The compounds were evaluated in vitro for their cytotoxic activity against select human cell lines.