Structurally diverse phthalides from fibrous roots of Ligusticum chuanxiong Hort. and their biological activities

Falonolide A (1) and B (2), two novel polyyne hybrid phthalides resulting from unprecedented carbon skeleton polymerized by Z-ligustilide and falcarindiol, along with six new related phthalides (3-8), were isolated from Ligusticum chuanxiong Hort. Their structures were elucidated by spectroscopic analysis, computer-assisted structure elucidation (CASE) analysis, DP4+ probability analysis and electronic circular dichroism (ECD) calculations. A plausible biosynthetic pathway for 1-8 was proposed, and the production mechanism of 2 was revealed by density functional theory (DFT) method. Compounds 4 and 6 exhibited significant vasodilatory activity with EC50 of 8.00 +/- 0.86 and 6.92 +/- 1.02 mu M, respectively. Compound 4 also displayed significant inhibitory effect of NO production with EC50 value of 8.82 +/- 0.30 mu M. Based on the established compounds library, structure-activity relationship analysis of phthalides was explored to provide insights into the drug development of vasodilators and anti-flammatory