Acute Oral Toxicity and Vasorelaxant Effects of Hydroethanolic Extract from <i>Lannea microcarpa</i> Engl. & K. Krause (Anacardiaceae) Trunk Barks in Mice Aortas: Possible Involvement of Intracellular Ca<sup> 2+</sup> Mobilization

Lannea microcrapa Engl. & K. Krause (Anacardiaceae) is a fruit and medicinal plant widely used in Burkina Faso. This plant is traditionally used in the treatment of hypertension. The aim of the present study was to evaluate the vasorelaxant effects of the hydroethanolic extract from Lannea microcarpa trunk barks (HE_ELM) on the aorta isolated from NMRI mice. Phytochemical screening by HPTLC, assay of phenolic and flavonoid compounds, assessment of antioxidant activity (DPPH, ABTS, FRAP, and LPO), and myography of HE_ELM (1 - 2000 μg/mL) on mice thoracic aortas in the presence and absence of endothelium were carried out. Endothelium-dependent and endothelium-independant vasodilation were assessed by cumulative addition of Ach (1 nM - 10 μM) on aortic rings precontracted with the thromboxane analogue A2 agonist, 9,11-dideoxy9α,11α-methanoepoxy PGF2α (U46619). L-NAME was used to verify the involvement of NO production in the relaxation mechanism of the extract. Acute oral toxicity of HE_ELM was also evaluated. A phytochemical study revealed the presence of tannins, flavonoids, sterols and triterpenes, saponosides, and high levels of total phenolics and flavonoids. These compounds are thought to be responsible for the extract’s antioxidant and vasorelaxant properties. HE_ELM demonstrated significant antioxidant potential and induced aortic relaxation. Indeed, pharmacological parameters gave EC50 values ranging from 596.45 ± 95.82 μg/mL to 749.48 ± 133.40 μg/mL and Emax values from 85.51% ± 9.59% to 96.81% ± 8.60% for the three conditions of vasodilation of the extract (p > 0.05). A complete antagonism of the contractile effect of U46619 was noted with 1 mg/mL HE_ELM. These results suggest that HE_ELM induces aortic relaxation through a concentration-dependent, endothelium-independent mechanism, possibly involving intracellular calcium mobilization of vascular cells. Acute oral toxicity tests of HE_ELM (2000 mg/kg) showed no mortality or adverse effects, suggesting the extract’s safety and potential as a therapeutic agent for hypertension. This discovery scientifically validates the use of the plant in alternative medicine to treat hypertension.