Ligustilide Reduces Phenylephrine Induced-Aortic Tension In Vitro but has No Effect on Systolic Pressure in Spontaneously Hypertensive Rats

Radix Angelica sinensis, known as Danggui in Chinese, has been used to treat cardiovascular diseases in traditional Chinese medicine for a long time. Experimental evidence showed that the essential oil of Danggui could reduce blood pressure in rabbits, cats or hypertensive dogs when given intravenously. In this study, we investigated the effects of Z-ligustilide, the main lipophilic component of the essential oil of Danggui on aortic tension induced by phenylephrine, an alpha-adrenergic agonist, in vitro and the systolic blood pressure in SHR rats. We demonstrated for the first time that ligustilide can significantly reduce the phenylephrine-induced aortic tension in vitro with IC 50 about 64 μg/ml, but has no in vivo effect on systolic blood pressure in SHR rats when administrated orally. The data on transport of ligustilide across Caco-2 monolayer suggested an efficient intestinal absorption of ligustilide in vivo, implying that the non-effectiveness of ligustilide in vivo is not due to the poor absorption in the gastrointestinal tract. Further studies on whether ligustilide is one of the main anti-hypertensive components of the essential oil are needed.