β-Cyclodextrin-complexed (-)-linalool produces antinociceptive effect superior to that of (-)-linalool in experimental pain protocols.

Many plants produce (-)-linalool, a plant-derived monoterpene alcohol, including members of the Lamiaceae (mints) and Lauraceae family (laurels, cinnamon, rosewood). The anti-inflammatory and analgesic effects of (-)-linalool have been widely suggested for various studies. Poor chemical stability and short half-life restrain the clinical applications of some essential oil and monoterpenes, including (-)-linalool. However, β-cyclodextrin (β-CD) has been used to increase solubility and stability of lipophilic compounds and also to improve the pharmacological effects. In this study, the antinociceptive effect of (-)-linalool and (-)-linalool/β-CD was examined using the acetic acid writhing reflex, formalin and hotplate tests in rodents. (-)-Linalool and (-)-linalool/β-CD demonstrated strong antinociceptive activity in all the chemical- and heat-induced mice models (p < 0.01 or p < 0.001). These findings imply the involvement of both peripheral and central antinociceptive mechanisms. In peritonitis induced by carrageenan, isolated monoterpene or β-CD complex also reduced total leucocyte migration and TNF-α levels in peritoneal fluid. The inclusion complexes, (-)-linalool/β-CD, revealed that the antinociceptive effect was significantly (p < 0.01) improved when compared with (-)-linalool alone. Such results were unlikely to be provoked by any motor abnormality. Together, our results suggest that β-CD might represent an important tool for improvement of analgesic and anti-inflammatory profiles of (-)-linalool and other water-insoluble compounds, such as lipophilic monoterpenes or essential oils.