Vasorelaxant effect of fennel seeds (Foeniculum vulgare Mill) extracts on rat mesenteric arteries: Assessment of phytochemical profiling and antioxidant potential.

Abstract

Ethnopharmacological relevance: Hypertension is a serious health problems and a leading cause of adult mortality worldwide. Foeniculum. vulgare Mill, a plant traditionally used for various ailments, including cardiovascular disorders such as hypertension.

Aim of the study: The objective of the study is to verify the vasorelaxant effect of fennel seeds on the isolated and perfused mesenteric vascular beds in rats.

Materials and methods: The vasorelaxant effect of the aqueous extract of F. vulgare (AEFv) seeds was tested on mesenteric arteries, both intact and denuded, precontracted with phenylephrine. Extracts from liquid-liquid extraction of F. vulgare were screened to find the active fraction. The mechanism of action of the active butanolic fraction (BFFv) was studied using inhibitors like L-NAME (nitric oxide synthase inhibitor), ODQ (guanylate cyclase inhibitor), indomethacin (cyclooxygenase inhibitor), potassium channel blockers (tetraethylammonium TEA, and glibenclamide), and atropine (a muscarinic receptor antagonist). Moreover, the antioxidant properties of AEFv and BFFv were evaluated using DPPH radical scavenging, β-carotene linoleic acid, and ferric-reducing power assays; total flavonoids and phenolics of AEFv and BFFv were measured using Folin-Ciocalteu and aluminum chloride colorimetric assays; HPLC-DAD analysis and acute toxicity of BFFv in mice were also performed.

Results: AEFv caused a concentration-dependent vasodilatory response in intact mesenteric arteries (E_max = 81.73 ± 0.36 %). This effect was significantly reduced after endothelium removal. The butanolic fraction showed the highest vasorelaxant effect. The vasodilatory effect was attenuated by L-NAME, ODQ, indomethacin, TEA, glibenclamide, and atropine, indicating involvement of the NO/GMPc pathway, potassium channels, and muscarinic receptors. Additionally, fennel extracts demonstrated excellent antioxidant activity and high concentrations of flavonoids and phenolic compounds. HPLC-DAD analysis of the butanolic fraction revealed an abundance of phenolic acids. Acute toxicity studies of BFFv showed no toxic effects.

Conclusion: Our findings support the traditional use of Foeniculum vulgare seeds for preventing cardiovascular disorders associated with vascular dysfunction, highlighting their vasorelaxant and antioxidant properties.