New dimeric phthalides from the rhizomes of Ligusticum sinense Oliv

Two new phthalide dimers (1 and 2) were obtained from the rhizomes of Ligusticum sinense Oliv., along with three known dimeric phthalides (3–5). Their structures were determined with the aid of the spectroscopic data, and their absolute configurations were elucidated based on the comparison of calculated and experimental electronic circular dichroism (ECD) spectra. All the compounds were evaluated in vitro for their inhibitory activities against NO production in LPS-treated RAW264.7 macrophages. Among them, compounds 1 and 3 showed potent NO prohibitive activity with IC50 values at 4.86 ± 0.29 μM and 4.87 ± 0.32 μM, respectively.