Monoterpenes Isolated from Minthostachys verticillata (Griseb.) Epling Essential Oil Modulates Immediate-Type Hypersensitivity Responses In Vitro and In Vivo

In a previous work, we have demonstrated that Minthostachys verticillata essential oil has immunomodulatory effects in vitro on cells from allergic patients. Here we characterized main components of M. verticillata essential oil and also tested if these compounds modulate in vitro and in vivo the immediate-type allergic reaction. Gas chromatography was used to identify main components of the essential oil. Pulegone (63.4%), menthone (15.9%), and limonene (2.1%) were found as main classes. IL-13 levels were evaluated from lymphocytes cultures stimulated with allergen alone or combined with monoterpenes. All compounds stimulated cell proliferation but, interestingly, promoted a reduction of IL-13 values, limonene and the mixture of the three compounds being the most active. beta-Hexosaminidase release was determined from basophils to which essential oil or monoterpenes were added. We observed that, whichever combination of monoterpenes was used, beta-hexosaminidase release was diminished in all cases. Obtained values were even lower than those of antiallergic drug desloratadine. Essential oil and limonene inhibited mast cell activation and degranulation in the skin when testing passive cutaneous anaphylaxis, limonene being the most active. In conclusion, limonene was the compound that showed the most potent immunomodulatory activity. This fact suggests that it constitutes a promising natural alternative for a novel treatment of allergic diseases.