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

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.

Effect of the Lippia alba (Mill.) N.E. Brown essential oil and its main constituents, citral and limonene, on the tracheal smooth muscle of rats.

The Lippia alba (Mill.) N.E. Brown (Verbenaceae) species, has effects sedative, analgesic and spasmolytic properties. This study had as its main objective to evaluate the essential oil of L. alba (EOLa) effect and that of its main constituents, citral and limonene, over tracheal smooth muscle from Wistar rats. EOLa, citral and limonene promoted relaxation of tracheal smooth muscle in contractions induced by potassium (60 mM K+), presenting an EC50 of 148 ±â€¯7 µg/mL for the EOLa, 136 ±â€¯7 µg/mL for citral and 581 ±â€¯7 µg/mL for limonene. In contractions induced by Acetylcholine (Ach; 10 µM) the EC50 for the EOLa and citral were of 731 ±â€¯5 µg/mL and 795 ±â€¯9 µg/mL, respectively. In preparations pre-incubated with 1000 µg/mL of the EOLa and citral, both agents were found to block the influx of BaCl2 by VOCCs. This study demonstrated that the EOLa and its main component citral present antispasmodic effect over tracheal smooth muscle of rats.