Natural products assessed in animal models for orofacial pain – a systematic review

ABSTRACT Orofacial pain is related to tissues of the head, face, neck and all the intraoral structures; it is rather debilitating to the patient and also difficult to treat. There are relatively few studies dedicated to the use of natural products to alleviate orofacial pain in preclinical experiment models (performed in experimental animals which provide support for clinical trials). Main objectives of the present systematic review summarize the studies on natural products assessed in animal models for orofacial pain seeking to give evidence to future development of new pharmaceutical products to manage the orofacial pain. Our review includes a thorough search of literature using the terms of orofacial pain, facial pain, medicinal plants and natural products. This search was performed using to retrieve English language articles in Medline-PubMed, Scopus and Web of Science. A total of eighteen studies were included in our survey for the inclusion criteria. Firstly, this review identified 210 citations from electronic search, after removal of duplicates and screening for relevant titles and abstracts, a total of eighteen articles were selected to the inclusion criteria established. Our findings suggest that natural products can be a promising or a trump tool for the development of new drugs to treat orofacial pain conditions, but the researchers that deal with experimental preclinical trials of new drugs (including natural products or synthetic drugs) for orofacial pain conditions urgently need to show translational evidence (with clinical approach) of these compounds.

Modelo de obesidade induzida por dieta hiperlipídica e associada à resistência à ação da insulina e intolerância à glicose / Model of high-fat diet-induced obesity associated to insulin resistance and glucose intolerance

OBJETIVO: Validar um modelo de obesidade induzida por dieta hiperlipídica, de baixo custo, fácil reprodutibilidade, que mimetizasse características observadas no humano e viabilizasse posteriores proposições terapêuticas. MATERIAIS E MÉTODOS: Dezesseis camundongos Swiss receberam dieta padrão (DP) ou dieta hiperlipídica (DH), durante 10 semanas. RESULTADOS: Embora o grupo DP tenha apresentado maior consumo de água (p < 0,01) e ração (p < 0,001), o grupo DH apresentou maior ganho de peso corpóreo (p < 0,5) e aumento de coxins adiposos (p < 0,001), favorecendo maior índice de adiposidade (p < 0,001), glicemia (p < 0,01) e área sob a curva nos testes de tolerância à insulina (p < 0,001) e à glicose (p < 0,01). CONCLUSÃO: Validou-se um modelo de obesidade induzida por dieta hiperlipídica associada à resistência à ação da insulina e à intolerância à glicose, em um período de 10 semanas.

OBJECTIVE: Validate a model of high-fat diet-induced obesity, of low cost, easy reproducibility, that could express characteristics observed in human, and would enable subsequent therapy proposals. MATERIALS AND METHODS: Sixteen Swiss mice received a standard diet (DP) or high-fat diet (DH) for 10 weeks. RESULTS: Although the DP group had greater water (p < 0.01) and feed (p < 0.001) consumption, the DH group had greater body weight (p < 0.5) and adipose tissue gain (p < 0.001), favoring higher adiposity index (p < 0.001), glucose (p < 0.01), and area under the curve in the insulin (p < 0.001) and glucose (p < 0.01) tolerance tests. CONCLUSION: A high-fat diet-induced obesity model has been validated, which was also associated with insulin resistance and glucose intolerance after a period of 10 weeks.

Evaluation of wound healing activity of atranorin, a lichen secondary metabolite, on rodents

The aim of this study was to investigate the wound healing activity of atranorin cream (Patent requested) on excision wounds. Seventy-two male rats were anesthetized and an excisional wound was performed. Then the rats were randomly assigned into three groups: untreated control group; atranorin 1 (group treated with 1% AT ointment); and atranorin 5 (group treated with 5% AT ointment). Six animals of each group were euthanized 3, 7, 14 or 21 days after surgical procedures and the wounded areas were analyzed and removed. Serial histological sections were obtained and stained by histochemical techniques (Hematoxilin-Eosin-HEand Sirius red) and immunohistochemical techniques. Topical application of atranorin reduced wound areas, induced earlier granulation tissue formation, increased cell proliferation, improved collagenization and modulated the myofibroblasts differentiation when compared to control animals. It is suggested that atranorin modulates the wound healing process. These data suggest that this formulation based on atranorin extracted from Cladina kalbii AHTI may be a new biotechnological product for wound healing clinical applications.

p-Cymene reduces orofacial nociceptive response in mice

This study investigated the possible antinociceptive effect of p-cymene in different tests of orofacial nociception. The animals (mice) were pretreated (i.p.) with p-cymene (25, 50, 100 mg/kg), morphine (5 mg/kg), or vehicle (0.2 percent Tween 80+saline), and were then subsequently administered, subcutaneously into their upper lip: formalin, capsaicin, and glutamate. The nociceptive behavior response was characterized by the time in s that the mice remained rubbing the orofacial region, for a period of 40 min in the formalin test (first phase, 0-6 min; and second phase, 21-40 min), and for 42 and 15 min in the capsaicin and glutamate tests, respectively. To verify the possible opioid involvement in the antinociceptive effects, naloxone (i.p.) was administered into the mice 15 min prior to the pretreatment with p-cymene (100 mg/kg). Finally, whether or not the p-cymene evoked any change in motor performance in the Rota-rod test was evaluated. The results showed that the treatment with p-cymene, at all doses, reduced (p<0.001) the nociceptive behavior in all nociception tests. The antinociceptive effect of p-cymene was antagonized by naloxone (1.5 mg/kg). Additionally, mice treated with p-cymene did not show any change in motor performance. In conclusion, p-cymene attenuated orofacial nociception, suggesting an involvement of the opioid system in this effect. Thus, p-cymene might represent an important biomolecule for management and/or treatment of orofacial pain.

Antinociceptive and anti-inflammatory effects of Caesalpinia pyramidalis in rodents

Caesalpinia pyramidalis Tul., Fabaceae, is a plant with an anti-inflammatory activity that is used in folk medicine. To evaluate the mechanism of action of this plant, studies were performed on its antinociceptive and anti-inflammatory properties using an ethanol extract (EE) made from the inner bark. Oral treatment of mice with the EE (100, 200, and 400 mg/kg) decreased their acetic acid-induced abdominal writhes (p<0.001) and their formalin-induced paw licking in both the first and second phases (p<0.001). This treatment increased the reaction time of mice on the hot-plate test (400 mg/kg, p<0.05); however, it did not alter their performance on the Rotarod performance test. The carrageenan-induced paw edema in the rats and the leukocyte migration into the peritoneal cavity of the mice were also reduced by the EE given at a dose of 400 mg/kg (p<0.05). In addition, the EE (100-400 mg/kg, v.o.) did not alter the arterial pressure of non-anesthetized rats. In conclusion, the EE of C. pyramidalis shows antinociceptive and anti-inflammatory activities in rodents, supporting the usage of this plant to treat various inflammatory diseases for which it has traditionally been used.

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.

Assessment of antinociceptive and anti-inflammatory activities of Porophyllum ruderale (Jacq.) Cass., Asteraceae, aqueous extract

The present work investigated the antinociceptive and antiinflammatory activities of the Porophyllum ruderale (Jacq.) Cass., Asteraceae, aqueous extract (PRAE). For this purpose, acetic acid writhing, paw licking induced by formalin, hot-plate and pleurisy tests were performed. The doses of 100, 200 and 400 mg/kg (p.o.) significantly inhibited the writhing 63.4, 89.6 and 94.8 percent, respectively, in comparison with control group. The lick of the paw 1st phase was reduced at the dose of 400 mg/ kg (24.9 percent), while the 2nd phase had reduction at doses 200 and 400 mg/ kg (23.1 and 34.4 percent), respectively. The PRAE inhibited the carrageenaninduced neutrophil migration to the peritoneal cavity in a higher dose (p<0.05). Taken together, our results suggest that the PRAE can constitute target potential for use in therapies of the pain and inflammation.

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.

Chemical composition and cardiovascular effects induced by the essential oil of Cymbopogon citratus DC. Stapf, Poaceae, in rats / Composição química e efeitos cardiovasculares do óleo essencial de Cymbopogon citratus DC. Stapf, Poaceae, em ratos

Cymbopogon citratus DC. Stapf, Poaceae, is used in the folk medicine for hypertension treatment. This work investigated the chemical composition and cardiovascular effects in rats of C. citratus essential oil (EOCC). A phytochemical screening demonstrated the presence of eight constituents, being geranial the major compound (43.08 percent). In rats, EOCC (1, 5, 10, and 20 mg/kg, i.v.) induced transient hypotension and bradycardia that were attenuated by atropine and sodium thiopental, but not by L-NAME or indomethacin. In rings of rat superior mesenteric artery pre-contracted with phenylephrine, EOCC (1 to 3000 µg/mL) induced relaxation that was not affected after removal of the endothelium, after TEA or in rings pre-contracted with KCl (80 mM). Furthermore, EOCC (1000 µg/mL) was not able to induce additional effect on maximal relaxation of nifedipine (10 µM). In conclusions, EOCC induces hypotension, possibly by reduction in vascular resistance caused by inhibition of the Ca2+ influx, and bradycardia probably due to an activation of cardiac muscarinic receptors.

C. citratus é utilizada na medicina popular para tratar hipertensão. Este trabalho investigou a composição química e os efeitos cardiovasculares do óleo essencial do C. citratus (OECC). Foram identificados oito constituintes no OECC, sendo geranial o majoritário (43,08 por cento). Em ratos, o OECC (1, 5, 10 e 20 mg/kg, i.v.) induziu hipotensão e bradicardia que foram atenuadas pela atropina e tiopental sódico, mas não por L-NAME ou indometacina. Em anéis de artéria mesentérica de ratos pré-contraídos com fenilefrina, o OECC (1 a 3000 µg/mL) induziu relaxamento que não foi afetado após remoção do endotélio, após TEA ou em anéis pré-contraídos com KCl (80 mM). Além disso, o OECC (1000 µg/mL) não induziu efeito adicional sobre o relaxamento máximo da nifedipina (10 µM). Em conclusão, o OECC induz hipotensão possivelmente devido à redução da resistência vascular que pode ser causada por inibição do influxo de Ca2+, e bradicardia provavelmente devido à ativação de receptores muscarínicos cardíacos.

Vasorelaxant effect of Hyptis fruticosa Salzm. ex Benth., Lamiaceae, dichloromethane extract on rat mesenteric artery / Efeito vasorelaxante do extrato diclorometano de Hyptis fruticosa Salzm. ex Benth., Lamiaceae, em artéria mesentérica de ratos

Vasorelaxant effect of Hyptis fruticosa dichloromethane extract (HFDE) on isolated rings of rat mesenteric artery was evaluated in this study. In intact rings, HFDE (0.1-3000 µg/mL) induced concentration-dependent vasorelaxations (Emax = 119±14 percent; n = 6) of phenylephrine tonus that were not modified after endothelium removal (Emax = 116±6 percent; n = 6), after KCl 20 mM (Emax = 135±9 percent; n = 6) or in rings pre-contracted with KCl 80 mM (Emax = 125±4 percent; n = 6). In endothelium denuded rings, HFDE (300 or 1000 µg/mL) inhibited contractions induced by CaCl2 (maximal inhibition = 25±7 percent and 95±1 percent; respectively). Furthermore, HFDE promoted an additional vasorelaxation (15±3 percent; n = 7) after maximal response of 10 µM nifedipine (78±3 percent; n = 7). In conclusion, HFDE induces vasorelaxant effect through an endothelium-independent pathway, which appears to be due in major part to inhibition of the Ca2+ influx through voltage-operated Ca2+ channels.

O efeito vasorelaxante do extrato diclorometano de Hyptis fruticosa Salzm. ex Benth., Lamiaceae (HFDE), em anéis isolados de artéria mesentérica de ratos foi avaliado nesse estudo. Em anéis intactos, pré-contraídos com fenilefrina (10 µM), HFDE (0,1-3000 µg/mL) induziu vasorelaxamento de maneira dependente de concentração (Emax = 119±14 por cento; n = 6), o qual não foi afetado após remoção do endotélio (Emax = 116±6 por cento; n = 6), após KCl 20 mM (Emax = 135±9 por cento; n = 6) ou em anéis pré-contraídos com KCl 80 mM (Emax = 125±4 por cento; n = 6). Em anéis sem endotélio, HFDE (300 ou 1000 µg/mL) inibiu as contrações induzidas por CaCl2 (inibição máxima = 25±7 por cento e 95±1 por cento, respectivamente). Além disso, HFDE promoveu um vasorelaxamento adicional (15±3 por cento; n = 7) sobre o relaxamento máximo de 10 µM de nifedipina (78±3 por cento, n = 7). Em conclusão, HFDE induz efeito vasorelaxante através de uma via independente de endotélio, possivelmente devido à inibição do influxo de Ca2+ através de canais de Ca2+ operados por voltagem.

Relaxant effect of the aqueous extract of Erythrina vellutina leaves on rat vas deferens

The effect of the Aqueous Extract from the leaves of Erythrina vellutina (AE) on rat vas deferens preparation was evaluated in this work. The AE inhibited the muscle contractions induced by electrical field stimulation (EFS) in a concentration-dependent manner. This inhibition was not affected by atropine (10-5M), propanolol (10-5M), prazosin (10-5M) or yohimbine (10-5M), suggesting that there is no direct interaction of the AE with cholinergic nor adrenergic receptors. Incubation of vas deferens with the K+ channel antagonists, tetraethylamonium (10-6M) or 4-aminopyridine (10-6M) had also no effect on the AE-induced inhibition. On the other hand, glibenclamide (10-6) significantly attenuated the effect of the AE, suggesting a possible involvement of ATP-dependent K+ channels. The AE (0.15 mg/mL) did not alter the contractions induced by noradrenaline (10-5M), ATP (10-4M) nor KCl (80 mM), against an interaction of the extract with post-synaptic sites. The data presented suggests that the inhibition of the electrically driven muscle twitches by the AE could be due to a pre-synaptic interaction of the extract with ATP-dependent K+ channels from vas deferens sympathetic neurons.

O objetivo deste trabalho foi avaliar o efeito do extrato aquoso das folhas de Erythrina vellutina (AE) sobre ducto deferente de rato. Nesta preparação, o AE inibiu as contrações induzidas por estímulo elétrico de campo de maneira dependente da concentração. Esta inibição não foi afetada após atropina (10-5M), propanolol (10-5M), prazosin (10-5M) ou yohimbina (10-5M), sugerindo uma ação indireta do AE sobre receptores colinérgicos ou adrenérgicos. A incubação da preparação com os antagonistas de canais de K+, tetraetilâmonio (10-6M) ou 4-aminopiridina (10-6M) não alterou o efeito inibitório induzido pelo AE. Entretanto, a glibenclamida (10-6M) atenuou significantemente este efeito, sugerindo um possível envolvimento de canais de K+ dependentes de ATP. Além disso, o AE (0.15 mg/mL) não alterou as contrações induzidas por noradrenalina (10-5M), ATP (10-4M) ou KCl (80 mM), descartando uma interação do AE com um sítio pós-sináptico. Em conclusão, estes resultados demonstram que o efeito inibitório do AE pode ser devido a uma interação pré-sináptica com canais de K+ dependentes de ATP em neurônios simpáticos de ducto deferente de rato.