The monoterpenes are the main constituents of most essential oils and p-cymene is a monoterpene commonly found in various species of aromatic herbs, which has been reported for anti-inflammatory, antinociceptive, and antimicrobial activities. However, there is no report concerning its pharmacological activity on the vascular smooth muscle. The aim of current work was to investigate the effects of p-cymene in isolated rat aorta and also study its mechanism of action. In this work, we show that p-cymene has a relaxant effect, in a dose-dependent way, on the vascular smooth muscle, regardless of the presence of the endothelium. Using a nonselective potassium channel blocker, the CsCl, the relaxant effect of p-cymene was attenuated. In the presence of more selective potassium channels blockers, such as TEA or 4-AP, no change in the relaxant effect of p-cymene was evidenced, indicating that BKCa and KV channels are not involved in that relaxant effect. However, in the presence of glibenclamide or BaCl2, KATP and Kir blockers, respectively, the relaxant effect of p-cymene was attenuated. The data presented indicate that p-cymene has a relaxing effect on rat aorta, regardless of the endothelium, but with the participation of the KATP and Kir channels.

Respiratory diseases are responsible for significant morbidity and mortality in worldwide. One of most important respiratory disease is asthma, which the current treatment is based on use of β 2 -agonists combined to inhaled corticosteroids. However, in recent years, many in vitro studies have attempted to validate the use of aromatic medicinal plants and its chemical compounds, such as monoterpenes, as potential therapeutically alternatives. In this work it was demonstrated that three different monoterpenes (carvacrol, citronellal and p-cymene) has relaxant effect in guinea-pig trachea, somehow showing different profile regarding epithelium presence, potency and efficacy.