Neophathalides A and B, two pairs of unusual phthalide analog enantiomers from Ligusticum chuanxiong

Two pairs of unusual phthalide analog enantiomers, (+)- and (−)-neophathalides A and B [(+)- and (−)-1 and 2], were isolated from the rhizome of Ligusticum chuanxiong Hort. Notably, neophathalide A presented a novel spiro-[4.5]dec-6-ene skeleton that originated from an aldol condensation process from sedanonic acid. Neophathalide B is an unprecedented 3-substituted phthalide analog that possesses a four-membered lactone ring system. The structures of the compounds were established using UV, IR, HRESIMS, NMR and ECD methods. All of the compounds were evaluated for their hepatoprotective activity against N-acetyl-p-aminophenol-induced HepG2 cell injury. Compounds 1a, 1b, and 2a exhibited moderate hepatoprotective activity compared with the positive control drug bicyclol at a concentration of 10 μM (p < 0.01).