Reinaldo Nóbrega de Almeida

Study of anticonvulsant effect of citronellol, a monoterpene alcohol, in rodents

Citronellol is one monoterpene alcohol, which is present in the essential oils of various aromatic plant species. This study evaluated the neuroprotective activity of citronellol on pentylenetetrazol- and picrotoxin-induced convulsions and maximal electroshock-induced seizures in mice. Administration of citronellol significantly reduced the number of animals of convulsion induced by pentylenetetrazol and eliminated the extensor reflex of maximal electroshock-induced seizures test in about 80% of the experimental animals. In addition, administration of citronellol showed protection in the pentylenetetrazol and picrotoxin tests by increasing the latency of clonic seizures. We also investigated the effect of citronellol in the rat isolated nerve using the single sucrose-gap technique. We showed that the amplitude of the compound action potential decreased more than 90% when the monoterpene was incubated for 30 min at 6.4 mM and we did not verify any effect on the repolarization of the compound action potential. Taken together, our results demonstrated an anticonvulsant activity of the citronellol that could be, at least in part, explained by the diminution of the action potential amplitude.

Plants with anticonvulsant properties: a review

Seizures are resistant to treatment with currently available anticonvulsant drugs in about 1 out of 3 patients with epilepsy. Thus, there is a need for new, more effective anticonvulsant drugs for intractable epilepsy. However, nature is a rich source of biological and chemical diversity and a number of plants in the world have been used in traditional medicine remedies, i.e., anticonvulsant, anxiolytic, analgesic, antidepressant. This work constitutes a literature review on medicinal plants showing anticonvulsant properties. The review refers to 16 Brazilian plants and a total 355 species, their families, geographical distribution, the utilized parts, method and references. Some aspects of research on medicinal plants and a brief review of the most common animal models to discover antiepileptic drugs are discussed. For this purpose over 170 references were consulted.

Anxiolytic-like effects of rose oil inhalation on the elevated plus-maze test in rats

The effect of rose oil inhalation (1.0%, 2.5%, and 5.0% w/w) on the elevated plus-maze (EPM) test was investigated in adult male rats and compared with the effect of diazepam (DZP) (1.0 and 2.0 mg/kg) administered intraperitoneally 30 min before testing. Exposure to rose oil produced an anxiolytic-like effect similar to DZP (anxiolytic reference drug). Thus, at some concentrations, rose oil significantly increased the number of visits to and time spent in the open arms of the EPM. Anxiolytic-like properties of rose oil were observed using the EPM, being consistent with other behavioral and clinical studies.

Natural products inhibitors of the angiotensin converting enzyme (ACE): a review between 1980 - 2000

Inhibition of Angiotensin Converting Enzyme (ACE) is a modern therapeutic target in the treatment of hypertension. Within the enzyme cascade of the renin-angiotensin system, ACE removes histidyl-leucine from angiotensin I to form the physiologically active octapeptide angiotensin II, one of the most potent known vasoconstrictors. Therefore, a rationale for treating hypertension would be to administer drugs or natural compounds which selectively inhibit ACE. The present work constitutes a review of the literature of plants and chemically defined molecules from natural sources with in vitro anti-hypertensive potential based on the inhibition of ACE. The review refers to 321 plants, the parts utilized, type of extract and whether they are active or not. It includes also the names of 158 compounds isolated from higher plants, marine sponges and algae, fungi and snake venom. Some aspects of recent research with natural products directed to produce anti-hypertensive drugs are discussed. In this review, 148 references were cited.

Antinociceptive and Antioxidant Activities of Phytol In Vivo and In Vitro Models.

The objective of the present study was to evaluate the antinociceptive effects of phytol using chemical and thermal models of nociception in mice and to assess its antioxidant effects in vitro. Phytol was administered intraperitoneally (i.p.) to mice at doses of 25, 50, 100, and 200 mg/kg. In the acetic acid-induced writhing test, phytol significantly reduced the number of contortions compared to the control group (P < 0.001). In the formalin test, phytol reduced significantly the amount of time spent in paw licking in both phases (the neurogenic and inflammatory phases), this effect being more pronounced in the second phase (P < 0.001). Phytol also provoked a significant increase in latency in the hot plate test. These antinociceptive effects did not impaire the motor performance, as shown in the rotarod test. Phytol demonstrated a strong antioxidant effect in vitro in its capacity to remove hydroxyl radicals and nitric oxide as well as to prevent the formation of thiobarbituric acid reactive substances (TBARS). Taken as a whole, these results show the pronounced antinociceptive effects of phytol in the nociception models used, both through its central and peripheral actions, but also its antioxidant properties demonstrated in the in vitro methods used.

Essential Oils and Their Constituents: Anticonvulsant Activity

A literature-based survey of plants species and their essential oils with anticonvulsant activity was carried out. As results, 30 species belonging to 13 families and 23 genera were identified for their activities in the experimental models used for anticonvulsant drug screening. Thirty chemical constituents of essential oils with anticonvulsant properties were described. Information on these 30 species is presented together with isolated bioactive compound studies.

Central depressant effects of reticuline extracted from Ocotea duckei in rats and mice

Neuropharmacological studies were carried out with reticuline, a benzylisoquinoline alkaloid, isolated from Ocotea duckei Vattimo. It was found that reticuline (50-100 mg/kg i.p.) produced alteration of behaviour pattern, prolongation of pentobarbital-induced sleep, reduction in motor coordination and D-amphetamine-induced hypermotility and suppression of the conditioned avoidance response. These observations suggest that reticuline possesses potent central nervous system depressant action.

Anxiolytic-like effects of inhaled linalool oxide in experimental mouse anxiety models

Linalool oxide is a monoterpene that is found in some species of aromatic plants. The effects of the inhalation of linalool oxide (0.65%, 1.25%, 2.5% and 5.0% w/w) in the elevated plus-maze and light/dark box tests as animal models of anxiety were investigated in adult male mice and compared with the effects of the reference anxiolytic diazepam (0.5 and 2.0 mg/kg), administered intraperitoneally. Additionally, the effects of inhaled linalool oxide were investigated in the rotarod test. Linalool oxide significantly increased the number of visits to the open arms of the elevated plus-maze and the amount of time spent there as well as the total number of entries. In the light/dark box test, inhalation of linalool oxide led to an increase in the time spent by the mice in the brightly-lit chamber and in the number of times the animal crossed from one compartment to another. Performance on the rotarod was unaffected. Thus, inhaled linalool oxide was found to have anxiolytic properties in both animal models, without causing any motor deficit. These results suggest that inhalation of linalool oxide may be a useful means of counteracting anxiety.

Behavioral effects of essential oil of Citrus aurantium L. inhalation in rats

The orange essential oil (OEO) and its components obtained from Citrus aurantium L. (Rutaceae) has been attracting interest due to its sedative and relaxing actions. In the present study, rats previously exposed to OEO at the concentrations of 1.0%; 2.5% and 5.0%, w/w, by inhalation during 7 minutes in acrylic boxes were evaluated in two anxiety models: elevated plus maze (EPM) and open-field. The OEO at the concentration of 2.5% increased both the time of the animals in the open arms of the EPM and the time of active social interaction in the open-field being longer than that of the diazepam group (1.5 mg/kg i.p). In conclusion, the decrease in the level of emotionality of the animals observed in the two experimental models suggests a possible central action, which is in agreement with the phytochemical profile of the oil under study, since it showed the presence of limonene (96.24%) and mircene (2.24%), components with a well-known depressant activity on the central nervous system.

α-Terpineol reduces nociceptive behavior in mice

Context: α-Terpineol (TPN) is a monoterpenoid alcohol present in the essential oils of several species of the Eucalyptus genus (Myrtaceae). Objective: TPN was assessed for its antinociceptive activity in rodents. Materials and methods: The antinociceptive effect of TPN was examined using the acetic acid writhing reflex, formalin, glutamate, and capsaicin-induced nociception tests. Results: TPN produced a significant (P < 0.01 or P < 0.001) analgesic effect by reduction at the early and late phases of paw licking and reduced the writhing reflex in mice (formalin and writhing tests, respectively). In the glutamate test, all doses of TPN produced significant (P < 0.01) nociceptive protection. When the capsaicin-induced nociception test was conducted, TPN produced dose-related inhibition of the nociceptive behavior. In addition, the results of a hot plate test showed central analgesic properties for TPN (P < 0.01 or P < 0.001). Such results were unlikely to be provoked by motor abnormality. Conclusion: Our results suggest that TPN might represent an important tool for management and/or treatment of painful conditions.