Vasorelaxant and Blood Pressure-Lowering Effects of Cnidium monnieri Fruit Ethanol Extract in Sprague Dawley and Spontaneously Hypertensive Rats

Abstract

Cnidium monnieri (L.) Cusson, a member of the Apiaceae family, is rich in coumarins, such as imperatorin and osthole. Cnidium monnieri fruit (CM) has a broad range of therapeutic potential that can be used in anti-bacterial, anti-cancer, and sexual dysfunction treatments. However, its efficacy in lowering blood pressure through vasodilation remains unknown. This study aimed to assess the potential therapeutic effect of CM 50% ethanol extract (CME) on hypertension and the mechanism of its vasorelaxant effect. CME (1-30 µg/mL) showed a concentration-dependent vasorelaxation on constricted aortic rings in Sprague Dawley rats induced by phenylephrine via an endothelium-independent mechanism. The vasorelaxant effect of CME was inhibited by blockers of voltage-dependent and Ca²⁺-activated K⁺ channels. Additionally, CME inhibited the vascular contraction induced by angiotensin II and CaCl₂. The main active compounds of CM, i.e., imperatorin (3-300 µM) and osthole (1-100 µM), showed a concentration-dependent vasorelaxation effect, with half-maximal effective concentration values of 9.14 ± 0.06 and 5.98 ± 0.06 µM, respectively. Orally administered CME significantly reduced the blood pressure of spontaneously hypertensive rats. Our research shows that CME is a promising treatment option for hypertension. However, further studies are required to fully elucidate its therapeutic potential.

Keywords: Cnidium monnieri fruit; hypertension; imperatorin; osthole; vasorelaxation.

Figure 1

Qualitative and quantitative HPLC analysis of osthole and imperatorin in the fruit of C. monnieri: (A) 50% ethanol extract (CME); (B) water extract (CMW). The retention times of the peak levels of imperatorin and osthole were 4.37 min and 5.25 min, respectively.

Figure 2

Vasorelaxant effects of C. monnieri 50% ethanol extract (CME) and water extract (CMW) on contractile responses induced by phenylephrine (PE): (A,C) Cumulative concentration–response curves and (B,D) representative traces of CME and CMW on endothelium-intact rat aortic rings pre-constricted with PE (1 μM). Unpaired t-test employed for statistical comparisons. Values are expressed as mean ± SEM (n = 4). ** p < 0.01 vs. control, *** p < 0.001 vs. control.

Figure 3

Vasorelaxant effects of C. monnieri 50% ethanol extract (CME) in endothelium-intact or endothelium-denuded rat aortic rings: (A) Cumulative concentration–response curves and (B) representative traces of CME on endothelium-intact [Endo (+)] or endothelium-denuded [Endo (−)] rat aortic rings pre-constricted with phenylephrine (PE, 1 μM). An unpaired t-test was employed for statistical comparisons. Values are expressed as mean ± SEM (n = 4). * p < 0.05, *** p < 0.001 vs. Endo(+) control. ## p < 0.01, ### p < 0.001 vs. Endo(−) control.

Figure 4

Effect of K⁺ channel blockers on C. monnieri 50% ethanol extract (CME)-induced vasorelaxation: (A) Cumulative concentration–response curves and (B) representative traces of rat aortic rings. K⁺ channel blockers included 4-aminopyridine (4-AP), tetraethylammonium (TEA), glibenclamide (Glib), and barium chloride (BaCl₂), and the aortic rings were pre-constricted with phenylephrine (PE, 1 μM). Statistical comparisons were conducted using an unpaired t-test. Values are presented as mean ± SEM (n = 5). * p < 0.05, *** p < 0.001 vs. CME.

Figure 5

Effect of C. monnieri 50% ethanol extract (CME) on extracellular Ca²⁺-induced contraction pre-treated with phenylephrine (PE) and KCl. Inhibitory effect of CME (30 and 300 µg/mL) induced by extracellular CaCl₂ (0.3–10 mM) constriction on aortic rings pre-treated with: (A) PE (1 μM), (C) KCl (60 mM), and (B,D) representative traces. Statistical comparisons were conducted using an unpaired t-test. Values are expressed as mean ± SEM (n = 4). * p < 0.05, *** p < 0.001 vs. control.

Figure 6

Effect of C. monnieri 50% ethanol extract (CME) and SK&F96365 on phenylephrine (PE)-induced contraction in the presence of nifedipine: (A) The effects and (B) traces of CME (30 µg/mL) on PE-induced contraction in the presence of nifedipine (10 µM). Statistical comparisons were conducted using an unpaired t-test. Values are expressed as mean ± SEM (n = 4). * p < 0.05, *** p < 0.001.

Figure 7

Inhibitory effects of C. monnieri 50% ethanol extract (CME) pre-treatment on angiotenin II (Ang II)-induced contraction. (A) Inhibitory effect and (B) representative original traces of CME (300 µg/mL) are shown in the contraction induced by Ang II (10⁻⁹–10⁻⁷ M) on the endothelium-intact aortic rings. Statistical comparisons were conducted using an unpaired t-test. Values are expressed as the mean ± SEM (n = 4). ** p < 0.01, *** p < 0.001 vs. control.

Figure 8

Vasorelaxant effect of the main active components in C. monnieri 50% ethanol extract (CME): (A,C) Cumulative concentration–response curves and (B,D) representative traces of imperatorin and osthole on endothelium-intact rat aortic rings pre-constricted with phenylephrine (PE, 1 μM). Statistical comparisons were conducted using an unpaired t-test. Values are expressed as mean ± SEM (n = 4). * p < 0.05, *** p < 0.001 vs. control.

Figure 9

Hypotensive effect of C. monnieri 50% ethanol extract (CME) in spontaneously hypertensive rats. Systolic blood pressure (A) and diastolic blood pressure (B) were measured at the baseline and 1, 2, 4, 8, and 12 h after CME (100, 300, and 1000 mg/kg, p.o.) administration. Amlodipine (1 mg/kg, i.p.) was used as a positive control. Vehicle group treated with dimethyl sulfoxide (DMSO, i.p.) in the same capacity as a solvent. Values are expressed as the mean ± SEM (n = 4). Two-way ANOVA and an unpaired t-test were used for statistical comparisons. * p < 0.05, ** p < 0.01, *** p < 0.001 vs. control. ## p < 0.01, ### p < 0.001 vs. vehicle (DMSO).

Figure 10

The morphology of Cnidium monnieri (L.) Cusson used in the experiment: (A) the fruit; (B) the whole plant. The photographs were taken before the experiment.