α-terpineol reduces mechanical hypernociception and inflammatory response.

α-Terpineol (TPN), a volatile monoterpene alcohol, is relatively non-toxic and one of the major components of the essential oils of various plant species. In this study, we tested for the antihypernociceptive activity of TPN (25, 50 or 100 mg/kg, i.p.) in mice using mechanical models of hypernociception induced by carrageenan (CG, 300 µg/paw) and the involvement of important mediators of its cascade signalling, such as tumour necrosis factor-α (TNF-α, 100 pg/paw), prostaglandin E2 (PGE2, 100 ng/paw) or dopamine (DA, 30 µg/paw). We also investigated the anti-inflammatory effect of TPN on the model of carrageenan-induced pleurisy and the LPS-induced nitrite production in murine macrophages. Pre-systemic treatment with TPN (25, 50 or 100 mg/kg, i.p.) inhibited the development of mechanical hypernociception induced by CG or TNF-α. A similar effect was also observed upon PGE2 and DA administration. In addition, TPN significantly inhibited the neutrophil influx in the pleurisy model. TPN (1, 10 and 100 µg/mL) also significantly reduced (p < 0.01) nitrite production in vitro. Our results provide information about the antinociceptive and anti-inflammatory properties of TPN on mechanical hypernociception and suggest that this compound might be potentially interesting in the development of new clinically relevant drugs for the management of painful and/or inflammatory disease.

Citronellol, a monoterpene alcohol, reduces nociceptive and inflammatory activities in rodents.

We describe the antinociceptive and anti-inflammatory properties of citronellol (CT) in rodents. CT, a monoterpene alcohol, is a naturally occurring monoterpene compound prevalent in essential oils of various aromatic plant species, such as Cymbopogon citratus. In mice, when evaluated against acetic-acid-induced abdominal writhing, CT (25, 50 and 100 mg/kg, i.p.) reduced (P < 0.001) the amount of writhing compared to the control group. In the formalin test, CT also significantly inhibited both the early (neurogenic pain) and the late (inflammatory pain) phases of formalin-induced licking (P < 0.001). When assessed in a thermal model of pain, CT (100 mg/kg, i.p.) caused a significant increase (P < 0.05) in the latency response on the hot-plate test. Such results were unlikely to be caused by motor abnormality. The anti-inflammatory activity of CT was investigated through carrageenan-induced pleurisy in mice. Pretreatment with CT was able to inhibit both neutrophil infiltration and the increase in TNF-α level in the exudates from carrageenan-induced pleurisy. In in vitro experiments, CT (1 and 100 µg/ml) also decreased nitric oxide production by LPS-stimulated macrophage. Together, these results indicate that CT is effective as an analgesic compound in various pain models, with its action probably mediated by the inhibition of peripheral mediators as well as central inhibitory mechanisms that could be related to its strong antioxidant effect observed in vitro.

Carvacrol attenuates mechanical hypernociception and inflammatory response.

Carvacrol is a phenolic monoterpene present in the essential oil of the family Lamiaceae, as in the genera Origanum and Thymus. We previously reported that carvacrol is effective as an analgesic compound in various nociceptive models, probably by inhibition of peripheral mediators that could be related with its strong antioxidant effect observed in vitro. In this study, the anti-hypernociceptive activity of carvacrol was tested in mice through models of mechanical hypernociception induced by carrageenan, and the involvement of important mediators of its signaling cascade, as tumor necrosis factor-alpha (TNF-α), prostaglandin E(2) (PGE(2)), and dopamine, were assessed. We also investigated the anti-inflammatory effect of carvacrol on the model of carrageenan-induced pleurisy and mouse paw edema, and the lipopolysaccharide (LPS)-induced nitrite production in murine macrophages was observed. Systemic pretreatment with carvacrol (50 or 100 mg/kg; i.p.) inhibited the development of mechanical hypernociception and edema induced by carrageenan and TNF-α; however, no effect was observed on hypernociception induced by PGE(2) and dopamine. Besides this, carvacrol significantly decreased TNF-α levels in pleural lavage and suppressed the recruitment of leukocytes without altering the morphological profile of these cells. Carvacrol (1, 10, and 100 µg/mL) also significantly reduced (p < 0.001) the LPS-induced nitrite production in vitro and did not produce citotoxicity in the murine peritoneal macrophages in vitro. The spontaneous locomotor activity of mice was not affected by carvacrol. This study adds information about the beneficial effects of carvacrol on mechanical hypernociception and inflammation. It also indicates that this monoterpene might be potentially interesting in the development of novel tools for management and/or treatment of painful conditions, including those related to inflammatory and prooxidant states.