Alkylphthalides isolated from Ligusticum wallichii franch and their in vitro inhibitory effect on rat uterine contraction induced by prostaglandin F₂α

From the neutral oil of Ligusticum wallichii Franch, three active constituents butylidenphthalide (Bdph), ligustilide (Lig.) and butylphthalide (Buph), were isolated and purified. Their structures were identified by combined gas chromatography-mass spectrometry. The structure-activity relationship was studied by comparison with other analogues. From the results of the experiment, it was suggested that the alkyl group substituted to the C-3 position of phthalide was very important. After the substitution, it might increase the lipid solubility so that it became easy to penetrate the cell membrane. The Δ³ double bond was also very important because it might enhance the inhibitory effect on rat uterine contraction induced by prostaglandin F₂ (α) The aromatization of phthalide also increased this kind of biological activity. Butylidenphthalide was found to be the most active constituent among these three, but its action mechanism still remains to be elucidated.