The monoterpene alcohol (−)‐borneol has many biological effects such as sedative, anti‐inflammatory, analgesic, anti‐nociceptive, antithrombotic and vasorelaxant effects. Our objective in this study was to investigate the mechanism of action of (−)‐borneol and determine its vasorelaxant effect. (−)‐Borneol was tested on isolated aortic rings contracted with PE (10−6 m). This study was performed in the absence or in the presence of endothelium, L‐NAME (100 μm), indomethacin (10 μm), TEA (1 and 10 mm), 4‐AP (1 mm) or glibenclamide (1 mm) to assess the participation of EDRF, nitric oxide, prostanoids and potassium channels on the relaxing effect of (−)‐borneol. In this work, (−)‐borneol induced a relaxant effect in aortic rings, with and without endothelium, in a concentration‐dependent manner. The pharmacological characterization obtained using L‐NAME, indomethacin, TEA, 4‐AP and glibenclamide demonstrates that the effect of (−)‐borneol was modified in the presence of L‐NAME, indomethacin and glibenclamide showing that these signal transduction pathways are involved in the relaxing effect of the monoterpene. (−)‐Borneol has a vasorelaxant effect that depends on the presence of vascular endothelium, with the participation of nitric oxide and prostanoids. Also, (−)‐borneol displayed a direct action on the vascular smooth muscle, greatly dependent on KATP channels.

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.

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