Phytochemical screening, antinociceptive and anti-inflammatory effects of the essential oil of Myrcia pubiflora in mice

This report aimed to investigate the chemical composition and possible antinociceptive and anti-inflammatory effects of the essential oil from fresh leaves of Myrcia pubiflora DC., Myrtaceae (EOMP), through different experimental tests. The essential oil of M. pubiflora (EOMP) was obtained by hydrodistillation, analyzed by GC-MS, and tested at doses of 25, 50, and 100 mg/kg (i.p.) in three different tests of nociception (acetic acid-induced writhing test, formalin test, and hot plate test) and one test of inflammation (leukocyte migration to the peritoneal cavity) in order to evaluate the motor activity in mice treated with EOMP. The major component of EOMP was caryophyllene oxide (22.16 percent). This oil significantly reduced the number of writhes in an acetic acid test and the time spent licking the paw at the second phase of the formalin test. Furthermore, EOMP inhibited the carrageenan-induced leukocyte migration to the peritoneal cavity. However, administration of EOMP did not alter reaction time in the hot plate test, and did not affect the motor coordination test. These results indicate antinociceptive and anti-inflammatory properties of EOMP probably mediated via inhibition of inflammatory mediator synthesis or other peripheral pathway.

Ocimum basilicum leaf essential oil and (-)-linalool reduce orofacial nociception in rodents: a behavioral and electrophysiological approach

The present study investigated the antinociceptive effects of Ocimum basilicum L. (Lamiaceae) leaf essential oil (LEO) and (-)-linalool (LIN) in formalin (2 percent)-, glutamate (25 µM)- and capsaicin (2.5 µg)- induced orofacial nociception models in mice. The involvement of these substances was further evaluated on the neuronal excitability of the hippocampal dentate gyrus. Male mice (n=8/group) were pretreated separately with LEO and by LIN (50, 100, and 200 mg/kg, i.p.), morphine (5 mg/kg, i.p.) and vehicle (saline + Tween 80 0.2 percent), before injection of nociceptive agent into the right upper lip (perinasal area). The LEO and LIN reduced the nociceptive face-rubbing behaviour in both phases on formalin test. LEO and LIN, at high doses, produced significantly antinociceptive effect in the capsaicin and glutamate tests. In hippocampal slices, LEO inhibited the population spike generated by stimulation of the hylus (antidromic stimulation), with an IC50 of 0.1±0.05 mg/mL. This response was reversibly blocked by lidocaine (0.5 mg/mL), a known voltage-dependent sodium channel antagonist and by LIN (0.5 mg/mL). Our results suggest that LEO and LIN modulate neurogenic and inflammatory pain in the tests of orofacial nociception induced by formalin, capsaicin and glutamate. Part of these effects may be associated with decreased peripheral and central neuronal excitability.

Bioassay-guided evaluation of central nervous system effects of citronellal in rodents

The central nervous system (CNS) depressant and anticonvulsant activities of citronellal (CT) were investigated in animal models. The CT in doses of 100, 200 and 400 mg/kg injected by i.p. route in mice caused a significant decrease in the motor activity of animals when compared with the control group. The highest dose of CT significantly reduced the remaining time of the animals on the Rota-rod apparatus up to 2 h. Additionally, CT at doses 100, 200 and 400 mg/ kg (i.p.) was also capable to promote an increase of latency for development of convulsions induced by pentylenetetrazole (PTZ). It was efficient in prevents the tonic convulsions induced by maximal electroshock (MES) in doses of 200 and 400 mg/kg, resulting in 30 and 40 percent of protection, respectively. This compound was also capable to promote an increase of latency for development of convulsions induced by picrotoxin (PIC) at 400 mg/kg. In the same way, the anticonvulsant effect of CT was affected by pretreatment with flumazenil, a selective antagonist of benzodiazepine site of GABA A receptor. These results suggest a possible CNS depressant and anticonvulsant activities.

Citral reduces nociceptive and inflammatory response in rodents

Citral (CIT), which contains the chiral enantiomers, neral (cis) and geranial (trans), is the majority monoterpene from Lippia alba and Cymbopogon citratus. The present study aimed to evaluate CIT for antinociceptive and anti-inflammatory activities in rodents. Antinociceptive and anti-inflammatory effects were studied by measuring nociception through acetic acid and formalin tests, while inflammation was verified by inducing peritonitis and paw edema with carrageenan. All tested doses of CIT had significant protection (p<0.001) against acetic acid (0.8 percent) induced nociceptive behavior and the effects were also similar to morphine while formalin induced nociception was significantly protected (p<0.05) only at higher dose (200 mg/kg) of CIT in the first phase of the test. CIT significantly reduce (p<0.001) nociceptive behavior emanating from inflammation in second phase at all the doses.The pretreatment with CIT (100 and 200 mg/kg) significantly reduced the paw edema induced by carrageenan. Moreover, systemic treatment with CIT (100 and 200 mg/kg) significantly reduced (p<0.001) the leukocyte migration in the carrageenan-induced migration to the peritoneal cavity. Our investigation shows that CIT possess significant central and peripheral antinociceptive effects. It was also verified an anti-inflammatory activity. All together these results suggest that CIT might represent important tool for treatment of painful conditions.