Chemical composition and vasorelaxant effect induced by the essential oil of Lippia alba (Mill.) N.E. Brown. (Verbenaceae) in rat mesenteric artery

Objectives: To investigate the chemical composition and vasorelaxant effect of the essential oil of Lippia alba (EOLA) in rat mesenteric artery.

Material and methods: Chemical composition of EOLA was investigated by gas chromatography-mass spectrometry (GC/MS). Vasorelaxant effect was evaluated in vitro in rat superior mesenteric artery rings.

Results: GC/MS analysis revealed the presence of 19 compounds, with geranial (48.58%) and neral (35.42%) being the major constituents. In intact rings precontracted with phenylephrine (Phe: 1 μM), EOLA (100-1000 μg/mL) induced relaxation, where the maximal effect (Emax) was 110.8 ± 10.8%. This effect was not modified after endothelium removal (Emax = 134.8 ± 16.5%), after tetraethylammonium (TEA) (Emax = 117.2 ± 4.96%), or in rings precontracted with KCl (80 mM) (Emax = 112.6 ± 6.70%). In addition, EOLA was able to inhibit the contraction caused by CaCl(2) and produced a small but significant (P<0.05) additional effect (from 70.5 ± 3.4 to 105.3 ± 13.5%, n = 5) on the maximal relaxation of nifedipine (NIF: 10 μM).

Conclusions: The results demonstrated that EOLA induces endothelium-independent vasorelaxation, which appears to be caused, at least in part, by blocking Ca(2+) influx through voltage-operated Ca(2+) channels.