Extract of Chenopodium album lowers blood pressure in rats through endothelium-dependent and -independent vasorelaxation

Abstract

Objectives: To investigate the antihypertensive effect of crude extract of Chenopodium album (Ca.Cr), based on its medicinal use in hypertension.

Methods: Ca.Cr and its fractions were tested in-vivo in normotensive anesthetized rats for blood pressure-lowering effect. In-vitro experiments were performed on isolated rat aortae to explore the vascular mechanism(s).

Results: In normotensive anesthetized rats, Ca.Cr produced a dose-dependent (1-300mg/kg) fall (30%mmHg) in mean arterial pressure (MAP). Among the fractions, nHexane was the most potent (46% fall). In rat aortic rings precontracted with phenylephrine (PE), Ca.Cr and its fractions (except Ca.Aq) produced endothelium-dependent vasorelaxation, which was partially reversed with endothelium removal and by pretreating intact aortic rings with L-NAME (10μM) and atropine (1μM). This relaxation to Ca.Cr and fractions (nHexane, ethylacetate and chloroform) was also eliminated with indomethacin pretreatment, however, it unmasked a vasoconstriction effect with Ca.Cr only. Surprisingly, the aqueous fraction produced a calcium sensitive strong vasoconstriction instead of vasorelaxation. The crude extract and its fractions (except Ca.Aq) also antagonized vasoconstriction induced with high K⁺ (80mM), suggesting calcium antagonistic effect. The aqueous fraction produced mild vasorelaxation against high K⁺. This effect was further confirmed when pretreatment of the aortic rings with different concentrations of crude extract and fractions suppressed CaCl₂ concentration response curves, similar to verapamil. In acute toxicity test, Ca.Cr extract was found safe up to 5g/kg body weight in mice.

Conclusion: These findings suggest that crude extract and fractions of C. album produced vasorelaxant effect through muscarinic receptors linked-NO pathway, prostaglandin (endothelium-dependent) and calcium antagonism (endothelium-independent), which explains the blood pressure lowering effect of C. album in rats.

Keywords: Antihypertenseur; Antihypertensive; Calcium channel blockers; Chenopodium album; Endothelium-dependent relaxation; Inhibiteurs calciques; Monoxyde d’azote (NO); Muscarinic receptors; Nitric oxide (NO); Relaxation dépendante de l’endothélium; Récepteurs muscariniques.