Lucindo J. Quintans-Júnior

Natural products inhibitors of the enzyme acetylcholinesterase

Alzheimers disease (AD) is a progressive, neurodegenerative pathology that primarily affects the elderly population, and is estimated to account for 50-60% of dementia cases in persons over 65 years of age. The main symptoms associated with AD involve cognitive dysfunction, primarily memory loss. Other features associated with the later stages of AD include language deficits, depression, behavioural problems including agitation, mood disturbances and psychosis. One of the most promising approaches for treating this disease is to enhance the acetylcholine level in the brain using acetylcholinesterase (AChE) inhibitors. The present work reviews the literature on plants and plant-derived compounds inhibitors of enzyme acetylcholinesterase. The review refers to 309 plant extracts and 260 compounds isolated from plants, which are classified in appropriate chemical groups and model tested, and cites their activity. For this purpose 175 references were consulted.

Monoterpenes with Analgesic Activity—A Systematic Review

There is still the need for efficacious therapies for pain. In the search for new therapeutic options, plants are a major source of novel biomolecules. Monoterpenes constitute 90% of essential oils, and there is a growing interest in understanding the mechanisms underlying their pharmacological activity. This systematic review reports what is so far known about the analgesic activity of monoterpenes and also provides an overview of their mechanisms of action. The search terms analgesia, anti‐inflammatory, anaesthetic and antioxidant were used to retrieve English language articles in SCOPUS, PUBMED and EMBASE published between 1990 and 2012. Forty‐five papers were found concerning the potential analgesic activity of 27 monoterpenes. The data reviewed here suggest these compounds are possible candidates for the treatment of painful conditions. Copyright

Bioassay‐guided Evaluation of Antioxidant and Antinociceptive Activities of Carvacrol

We examined the antioxidant properties in vitro and the antinociceptive effect of carvacrol (CARV) in several models of pain in mice. CARV presented a strong antioxidant potential according to the TRAP/TAR evaluation; it also presented scavenger activity against nitric oxide and prevented lipid peroxidation in vitro. In mice, when evaluated against acetic acid-induced abdominal writhing, CARV (25, 50 and 100 mg/kg, i.p.) reduced (p < 0.001) the number of writhing compared to the control group, without opioid participation. In the formalin test, CARV also significantly inhibited both the early (neurogenic pain) and the late (inflammatory pain) phases of formalin-induced licking, with inhibition percentage values of 56.8% (100 mg/kg) for the neurogenic phase and 41.2% (25 mg/kg), 73.8% (50 mg/kg) and 99.7% (100 mg/kg) for the inflammatory phase. CARV also produced a significant inhibition of the pain caused by capsaicin (63.1, 67.1 and 95.8%, p < 0.001) and glutamate (46.4, 61.4 and 97.9%, p < 0.01). When assessed in a thermal model of pain, CARV (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 provoked by motor abnormality. Together, these results indicate that the properties of CARV should be more thoroughly examined in order to achieve newer tools for management and/or treatment of painful conditions, including those related to pro-oxidant states.

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.

Cardiovascular effects of monoterpenes: a review

The monoterpenes are secondary metabolites of plants. They have various pharmacological properties including antifungal, antibacterial, antioxidant, anticancer, anti-spasmodic, hypotensive, and vasorelaxant. The purpose of this research was to review the cardiovascular effects of monoterpenes. The data in this resarch were collected using the Internet portals Pubmed, Scopus, and ISI Web of Knowledge between the years 1987 and 2010. In the study 33 monoterpenes were included, which were related to each of the thirteen individual words: artery, cardiovascular, heart, myocyte, vasorelaxant, vessel, hypotension, hypotensive, cardiomyocyte, ventricular, vasodilatory, aorta, and aortic. The research utilized 22 articles published mainly in the journals Phytomedicine, Fundamental Clinical Pharmacology, Planta Medica, Life Science, European Journal of Pharmacology, and Brazilian Journal of Medical and Biological Research. Of the 33 monoterpenes studied surveyed, sixteen of them had already been studied for their effects on the cardiovascular system: carvacrol, citronellol, p-cymene, eucalyptol (1,8-cineole), linalool, menthol, myrtenal, myrtenol, α-pinene, rotundifolone (piperitenone oxide), sobrerol, thymol, α-limonene, α-terpinen-4-ol, α-terpineol, and perillyl alcohol. The main effects observed were vasorelaxation, decreased heart rate and blood pressure. This review showed that the monoterpenes may be considered promising agents for prevention or treatment of diseases of the cardiovascular system.

Anti-inflammatory effects of carvacrol: Evidence for a key role of interleukin-10

Carvacrol, a phenolic monoterpene, has been reported to possess anti-inflammatory properties. However, the mechanisms involved in its pharmacological properties are currently not well understood. In the present study, the contribution of cytokine modulation to the anti-inflammatory effects of carvacrol was investigated in a classical inflammation model: the complete Freunds adjuvant (CFA)-induced paw inflammation in mice. The paw edema was measured using a plesthismometer. Paw tissue was removed 2h after the inflammatory stimulus to determine the levels of prostaglandin E(2) (PGE(2)) by enzyme immunoassay, the levels of interleukin-1 β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-10 (IL-10) by ELISA or the mRNA expression of cyclooxygenase-2 (COX-2), IL-1β, TNF-α, and IL-10 by real-time PCR. Administration of carvacrol produced anti-inflammatory effects against CFA-induced inflammation in mice. Treatment of mice with carvacrol at 50 and 100mg/kg attenuated the paw edema and reduced the IL-1β and PGE(2), but not TNF-α, local levels. Similarly, carvacrol (100mg/kg) reduced the COX-2 and IL-1β mRNA expression. The levels of IL-10, an anti-inflammatory cytokine, and the IL-10 mRNA expression in the inflamed paw were enhanced by carvacrol. In addition, the treatment with carvacrol did not reduce the CFA-induced paw edema in IL-10 knockout mice. The present results suggest that carvacrol causes anti-inflammatory effects by reducing the production of inflammatory mediators, such as IL-1β and prostanoids, possibly through the induction of IL-10 release.

Improvement of p-cymene antinociceptive and anti-inflammatory effects by inclusion in β-cyclodextrin.

Previously, we have demonstrated the analgesic-like property of p-cymene in rodents. Short half-life is a limitation for p-cymene application and several approaches have been used to improve pharmaceutical properties of monoterpenes, including the employment of drug-delivery systems. Here, we used p-cymene/β-cyclodextrin (β-CD) complex and p-cymene (PC) isolated to evaluated whether the complex formulation is able to improve the antinociceptive activity of this monoterpene. Male mice (26-30g) were pretreated with PC/β-CD (20 or 40mg/kg, p.o.), PC (20 or 40mg/kg, p.o.) or vehicle (distilled water), 0.5h before painful tests and antinociceptive effect was evaluated at times: 0.5, 1, 2, 4, 8, and 16h after treatment. We evaluated the analgesic-like effect of PC/β-CD and PC in acetic acid-induced abdominal writhes, hot-plate, carrageenan-induced paw edema and in rota-rod apparatus. Our results demonstrated that acute treatment with complex PC/β-CD produced an antinocicepitve effect (p<0.01 or p<0.001) for 8h followed whereas isolated PC produced the same effect for 2h. Similar results were obtained in hot-plate test, PC/β-CD, in all doses, significantly reduces (p<0.01 or p<0.001) nociceptive behavior for 8h while isolated PC for 1h, did so only in higher dose. Such results were unlikely to be caused by motor abnormality. Systemic pretreatment with PC/β-CD and PC inhibited the development paw edema by carrageenan 1%, but PC/β-CD did so during a longer period when compared with isolated monoterpene alone. Our results provide evidence to propose that the complex with β-CD improved analgesic and anti-inflammatory effects of p-cymene.

Anti-Inflammatory and Anti-Ulcer Activities of Carvacrol, a Monoterpene Present in the Essential Oil of Oregano

This study reports a pharmacological evaluation of anti-inflammatory and anti-ulcer activities of carvacrol, a phenolic monoterpene constituent of essential oils produced by oregano and other several aromatic plants and spices, in experimental models of edema induced by different phlogistic agents and gastric lesions induced by acetic acid. In models of paw edema induced by dextran or histamine, carvacrol was effective at 50 mg/kg (46% and 35%, respectively); in these models, cyproheptadine reduced edema formation (61% and 43%, respectively). In edema induced by substance P, carvacrol (100 mg/kg) and ruthenium red (3 mg/kg) also decreased the edema formation (46% and 40%, respectively). Carvacrol significantly reduced the ear edema induced by 12-O-tetradecanoylphorbol acetate and arachidonic acid at 0.1 mg per ear (43% and 33%, respectively), similar to indomethacin at 0.5 mg per ear or 2.0 mg per ear (55% and 57%, respectively). Carvacrol (at doses of 25, 50, and 100 mg/kg) showed a healing capacity on gastric lesions induced by acid acetic (60%, 91%, and 81%, respectively) after 14 days of treatment. These results suggest that carvacrol acts on different pharmacological targets, probably interfering in release and/or synthesis of inflammatory mediators, such as the prostanoids, and thus favoring the healing process for gastric ulcers.

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.

Terpenes and derivatives as a new perspective for pain treatment: a patent review

Introduction: Terpenes are natural compounds found in several organisms belonging to the animal and plant kingdoms. They constitute the largest class of natural products with > 55,000 known compounds structurally diversified. Several studies have attributed to this big family of compounds a range of pharmacological properties, such as anticancer, antimicrobial, antifungal, antiviral, antihyperglycemic, analgesic, anti-inflammatory and antiparasitic. Areas covered: In this review, the authors summarize therapeutic patent applications concerning the employment of terpenes for pain relief, focusing on the perspective for these compounds to become candidates for new drugs intended to control painful syndromes. Expert opinion: Over years of tremendous academic and industrial investment in the characterization of the analgesic action of terpenes, there was the development of a successful product that has been well-accepted clinically. Furthermore, there is still hope that new therapeutic options for the control of painful syndromes will be developed from terpenes, which have been shown to be great candidates for this purpose because of the range of pharmacological mechanisms in important target sites.