(؊)-Carvone is a monoterpene ketone that is the main active component of Mentha plant species like Mentha spicata. This study aimed to investigate the antinociceptive activity of (؊)-carvone using different experimental models of pain and to investigate whether such effects might be involved in the nervous excitability elicited by others monoterpenes. In the acetic acid-induced writhing test, we observed that (؊)-carvone-treated mice exhibited a significant decrease in the number of writhes when 100 and 200 mg/kg was administered. It was also demonstrated that (؊)-carvone inhibited the licking response of the injected paw when 100 and 200 mg/kg was administered (i.p.) to mice in the first and second phases of the formalin test. Since naloxone (5 mg/kg, s.c.), an opioid antagonist, showed no influence on the antinociceptive action of (؊)-carvone (100 mg/kg), this suggested nonparticipation of the opioid system in the modulation of pain induced by (؊)-carvone. Such results were unlikely to be provoked by motor abnormality, since (؊)-carvone-treated mice did not exhibit any performance alteration on the Rota-rod apparatus. Because the antinociceptive effects could be associated with neuronal excitability inhibition, we performed the single sucrose gap technique and observed that (؊)-carvone (10 mM) was able to reduce the excitability of the isolated sciatic nerve through a diminution of the compound action potential amplitude by about 50% from control recordings. We conclude that (؊)-carvone has antinociceptive activity associated with decreased peripheral nerve excitability.

The aim of the present work was to develop a biochemical, histologic and immunohistochemical study about the potential hepatotoxic effect of d-limonene – a component of volatile oils extracted from citrus plants. Blood alkaline phosphatase (ALP), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) from d-limonene-treated animals were determined and compared to morphologic hepatic lesions in order to investigate the possible physiopathologic mechanisms involved in the liver toxicity, in experimental animals treated with d-limonene. Wistar rats were randomly divided into seven groups: two control groups (untreated or receiving only vehicle, tween-80); one positive control (vehicle); two experimental groups treated with d-limonene at doses of 25 mg/kg/day and 75 mg/kg/day for 45 days, and two other groups treated with the same doses for 30 days and kept under observation during 30 more days. Biochemical data showed significant reduction in ALT levels in the animals treated with 75 mg/kg of d-limonene. Histological analysis revealed some hepatocyte morphological lesions, including hydropic degeneration, microvesicular steatosis and necrosis, Kupffer cell hyperplasia and incipient fibrosis. By immunohistochemistry, influx of T (CD3+) and cytotoxic (CD8+) lymphocytes was observed in the rats treated with d-limonene at both dose levels. In conclusion, it is possible that d-limonene has been directly responsible for hepatic parenchymal and matrix damage following subchronic treatment with d-limonene.

Farnesol, a sesquiterpene alcohol, has been shown to have antioxidant and anti-inflammatory properties. Recent studies have found that antioxidant compounds may exert a certain protective effect against neurotoxicity. The objective of this study was to evaluate the antinociceptive activity of farnesol (FAR) and its neurotoxic effects on the brains of adult mice. In this study, two mouse models of analgesia were used to evaluate FAR at doses of 50, 100, and 200 mg/kg, injected intraperitoneally (i.p.). In the acetic acid-induced writhing test, a significant decrease was found in the number of contortions in the FAR-treated mice at doses of 50, 100, and 200 mg/kg. FAR was also found to inhibit the licking response in the injected paw at doses of 100 and 200 mg/kg (i.p.) in the first (0-5 min) and second phases (15-30 min) of the formalin test. To evaluate neurotoxic effects, Swiss mice were treated with 0.9% saline (i.p., control group), 0.05 Tween 80 dissolved in 0.9% saline (i.p., vehicle group), and FAR 50, 100, or 200 mg/kg, i.p. Following treatment, all groups were observed for 72 h. In the FAR 200-mg group, 16% of the animals suffered brain injury that affected 12% of the area of the hippocampus. No lesions were found in the hippocampal and striatal regions of the brain in any of the animals treated with the 50 and 100 mg/kg doses of FAR. In conclusion, FAR exerts an antinociceptive effect with no significant neurotoxicity in the brains of adult mice.

Perillyl alcohol (PA) is a natural compound found in essential oils. In this study, the antinociceptive activity of PA was evaluated using acetic acid and formalin tests. The involvement of the opioid system in its mechanism of action was investigated. Potential histological changes in the hippocampus and striatum were also assessed. In the acetic acid induced writhing tests, the mice pretreated with PA exhibited significant reductions in writhing. PA inhibited formalin injected paw licking response, and naloxone partially reversed the antinociceptive activity of perillyl alcohol during the writhing test. And as for the histopathological evaluation, PA did not cause significant tissue changes. This study suggests that PA possesses antinociceptive effects without significant hippocampus or striatum neurotoxicity, and that its activity involves opioid.

It has been widely reported that the crude oil of Nigella sativa L., Ranunculaceae, seeds and its major chemical component thymoquinone present anticonvulsant activity. These facts led us to verify the pharmacological potential of five structurally related para-benzoquinones on the pentylenotetrazol-induced seizures model, and establish the structural characteristics that influence the anticonvulsant activity of thymoquinone. The unsubstituted para-benzoquinone was the compound that exhibited the highest potency, while 2-methyl-p-benzoquinone was inactive. It was found that the presence of alkyl groups attached to the ring influence the pharmacological activity of the para-benzoquinones. In addition, the number, position, and size of these groups change the anticonvulsant potency of the compounds.