Characterization of the vasodilator effect of eugenol in isolated human umbilical cord arteries.

Eugenol (EUG) is a phenylpropanoid widely used in the food and cosmetic industries. It is commonly referred to in the literature by its biological activities such as antioxidant, anti-inflammatory, antimicrobial, and relaxing in organs of laboratory animals, especially in rodent vessels. However, its vasorelaxant potential in human tissue, has not been investigated. Thus, this study characterizes the vasodilatory effect of EUG in the human umbilical artery (HUA). HUAs were isolated, cleaned, sectioned (3-4 mm) and placed in an organ bath (10 mL Krebs Henseleit, 37 °C; and carbogenic mixture). EUG (100-1400 µM), obtained total relaxation of electromechanical contractions induced by KCl (60 mM), and pharmacomechanical contractions (30-1200 µM), induced by serotonin (10 µM) and by histamine (10 µM), showing statistically significant concentrations: 600 µM, 400 µM and 200 µM, and EC50 values: 759.8 ± 6.5 µM, 229.9 ± 7.9 and 279.0 ± 3.4 µM, respectively. EUG (1200 and 1400 µM) prevented the contraction promoted by BaCl2 (0.1-30 mM), similar to the effects of nifedipine (10 µM), sugesting the involvement of EUG in blocking VOCCs. In the presence of tetraethylammonium (10 µM), EUG (30-1200 µM) did not produce a total relaxation (88.6%), suggesting that an alternative pathway where potassium channels, may partially mediate EUG effect. In the presence of 4-aminopyridine (1 mM), glibenclamide (10 µM), and tetraethylammonium (1 mM), EUG relaxed HUAs 100%, although the pharmacological potency was statistically altered, demonstrating the participation of K+ channels (Kv, KATP, BKCa). Our data indicates that EUG has a vasorelaxant effect on HUAs, had a greater pharmacological potency in the serotoninergic pathway, showing effective participation of VOCCs and a partial modulation of K+ channels. These data suggest new possibilities for the use of EUG in human vascular dysfunctions, such as preeclampsia. More studies are necessary to confirm the safety and effectivity in future treatments.

Myorelaxant action of the Dysphania ambrosioides (L.) Mosyakin & Clemants essential oil and its major constituent α-terpinene in isolated rat trachea.

This study aimed to investigate the myorelaxant action of the Dysphania ambrosioides essential oil (EODa) and its major constituent α-terpinene on tracheal smooth muscle isolated from rats. In tracheal smooth muscle ex vivo, in organ baths, isometric contractions recordings were done in order to evaluated the effect of EODa (1-1000 µg/mL) and α-terpinene (1-3000 µg/mL) on the following parameters: basal tone, contractions evoked by potassium (KCl 60 mM), acetylcholine (ACh 10 µM) or serotonin (5-HT 10 µM). The EODa and its major constituent α-terpinene, did not statistically alter basal tone; however, they induced myorelaxant effects on top of contractions induced by KCl, ACh and 5-HT. EODa and α-terpinene also inhibited the contractions induced by barium in presence of High [K+] (80 mM). The data suggest that the relaxation induced by these agents is caused by the inhibition of L-type VGCC, inhibiting the inward Ca2+ current through these channels, but does not exclude the possibility of participation of other mechanisms. Results from this study also suggest the EODa, due to their efficacy on relaxation of the respiratory tract, posses a therapeutic potential as a antispasmodic agent for respiratory tract.

Tocolytic activity of the Lippia alba essential oil and its major constituents, citral and limonene, on the isolated uterus of rats.

The species Lippia alba (Mill.) N. E. Brown belongs to the Verbenaceae family. It is abundant and grows spontaneously throughout the Brazilian territory. Popularly known as "erva-cidreira", it is widely used because of its sedative, carminative and analgesic properties. The objective of this study was to investigate the mechanism of action of the L. alba essential oil (EOLa) and its major constituents citral and limonene, on isolated rat uterus muscle. To evaluate the EOLa, citral and limonene effect, cumulative concentrations curves for EOLa and citral (1-600 µg/mL) and for limonene (1-1200 µg/mL) were constructed from contractions of rat uterine strips under a 1 g tension. EOLa, citral and limonene dose-dependently relaxed myometrial preparations pre-contracted with 60 mM KCl, 10-2 IU/mL oxytocin, serotonin (10 µM), or ACh (10 µM). The results demonstrate that the EOLa, citral and limonene cause relaxation of the uterine smooth muscle. These results suggest that the relaxation induced by EOLa, citral and limonene is caused by inhibition of L-type VOCC, inhibiting the Ca2+ current through these channels, although other mechanisms of action are likely to contributing to relaxant activity. There was no involvement of K+ channels (BKca, KATP, KV) or cyclooxygenase on the relaxation promoted by EOLa. Then studies of the tocolytic effects of EOLa, citral and limonene may yield new insights into their therapeutic use.