Effect of Lippia alba (Mill.) N.E. Brown Essential Oil on the Human Umbilical Artery

Abstract

Lippia alba is popularly known as lemon balm, with its essential oil (EO) cited for displaying antimicrobial, sedative, and vasorelaxant effects. Yet, its action on isolated human vessels has not been described in the literature. Thus, we evaluated the vasorelaxant effect of essential oil of L. alba (EOLa) on human umbilical arteries (HUA) isolated in organ baths. HUA rings were isolated, subjected to contractions induced by potassium chloride (KCl), serotonin (5-HT), or histamine (HIST) to record the isometric tension, and then treated with EOLa (30–1000 µg/mL). The EOLa showed a more prominent inhibitory effect on the pharmacomechanical coupling contraction via HIST with an EC50 value of 277.1 ± 8.5 µg/mL and maximum relaxant effect at 600 µg/mL. The addition of tetraethylammonium (TEA) or 4-aminopyridine (4-AP) in HUA preparations did not inhibit EOLa total relaxant effect at 1000 µg/mL. In the presence of gliblenclamide (GLI), the oil relaxed the HUA rings by 90.8% at maximum concentration. The EOLa was also investigated for its effects on voltage-operated calcium channels (VOCCs), where the HUA preincubation with this oil at 1000 μg/mL inhibited BaCl2 (0.1–30 mM)-induced contractions. This study demonstrates for the first time that EOla has a vasorelaxant effect on HUA and its particular blockade of VOCCs.

Vasodilation promoted by (E,E)-farnesol involving ion channels in human umbilical arteries

“…The greater pharmacological potency of ( E , E )-FAR in the electromechanical pathway in HUA directed us to investigate the influence of Ca 2+ and K + ion channels on the vasodilator effect. We observed that ( E , E )-FAR (800 μmol/L) suppressed contractions evoked by Ca 2+ and Ba 2+ ions more effectively than the control nifedipine which, in turn, is a potent inhibitor of Ca 2+ [ 31 ] and Ba 2+ [ 16 , 17 , 19 ] induced contractions in HUA.…”

“…The involvement of K + channels in the vasodilator effect of ( E , E )-FAR was verified after pre-contraction by 5-HT (10 μmol/L) for 15 min followed by pre-incubation (25 ± 5 min) of HUA rings with each of the following blockers at concentrations standardized for umbilical vessel rings [ 19 , 20 ], nonselective TEA (10 mmol/L), TEA (1 mmol/L) for BK Ca channels and K V channels, GLI (10 μmol/L) for K ATP channels, 4-AP (1 mmol/L) for K V channels, or BaCl 2 (500 μmol/L) for K IR channels. Subsequently, concentration-response curves were obtained with ( E , E )-FAR (1 μmol/L to 1 mmol/L).…”