Phytochemical screening, antinociceptive and anti-inflammatory activities of Chrysopogon zizanioides essential oil

Chrysopogon zizanioides (L.) Roberty, Poaceae, is a plant widely used in northeast Brazil in folk medicine for the treatment of various pathological conditions, including inflammatory pain. The present study evaluated the antinociceptive and anti-inflammatory effects of C. zizanioides essential oil (EO) in rodents. EO was further characterized by GC/MS. The major components of EO were identified as khusimol (19.57%), E-isovalencenol (13.24%), α-vetivone (5.25%), β-vetivone (4.87%) and hydroxy-valencene (4.64%). Following intraperitoneal injection (i.p.), EO at 50 and 100 mg/kg significantly reduced the number of writhes (51.9 and 64.9%, respectively) and the number of paw licks during phase 2 (56.7 and 86.2%, respectively) of a formalin model when compared to control group animals. However, EO-treated mice were ineffective at all doses in hot-plate and rota-rod tests. The EO inhibited the carrageenan-induced leukocyte migration to the peritoneal cavity in a dose-dependent manner (34.7, 35.4, and 62.5% at doses of 25, 50 and 100 mg/kg, respectively). In the paw edema test, the EO (100 mg/kg) inhibited all three phases of the edema equally well, suggesting that the EO has a non-selective inhibitory effect on the release or actions of these mediators. Our results suggest possible antinociceptive and anti-inflammatory effects of the EO.

Carvacrol attenuates mechanical hypernociception and inflammatory response.

Carvacrol is a phenolic monoterpene present in the essential oil of the family Lamiaceae, as in the genera Origanum and Thymus. We previously reported that carvacrol is effective as an analgesic compound in various nociceptive models, probably by inhibition of peripheral mediators that could be related with its strong antioxidant effect observed in vitro. In this study, the anti-hypernociceptive activity of carvacrol was tested in mice through models of mechanical hypernociception induced by carrageenan, and the involvement of important mediators of its signaling cascade, as tumor necrosis factor-alpha (TNF-α), prostaglandin E(2) (PGE(2)), and dopamine, were assessed. We also investigated the anti-inflammatory effect of carvacrol on the model of carrageenan-induced pleurisy and mouse paw edema, and the lipopolysaccharide (LPS)-induced nitrite production in murine macrophages was observed. Systemic pretreatment with carvacrol (50 or 100 mg/kg; i.p.) inhibited the development of mechanical hypernociception and edema induced by carrageenan and TNF-α; however, no effect was observed on hypernociception induced by PGE(2) and dopamine. Besides this, carvacrol significantly decreased TNF-α levels in pleural lavage and suppressed the recruitment of leukocytes without altering the morphological profile of these cells. Carvacrol (1, 10, and 100 µg/mL) also significantly reduced (p < 0.001) the LPS-induced nitrite production in vitro and did not produce citotoxicity in the murine peritoneal macrophages in vitro. The spontaneous locomotor activity of mice was not affected by carvacrol. This study adds information about the beneficial effects of carvacrol on mechanical hypernociception and inflammation. It also indicates that this monoterpene might be potentially interesting in the development of novel tools for management and/or treatment of painful conditions, including those related to inflammatory and prooxidant states.

Investigation of mechanisms involved in (-)-borneol-induced vasorelaxant response on rat thoracic aorta.

The monoterpene (-)-borneol is present in essential oils of several medicinal plants. The aim of this study was to evaluate (-)-borneol effects on rat thoracic aorta artery rings. The cumulative addition of (-)-borneol (10(-9) -3 × 10(-4) M) on a phenylephrine-induced pre-contraction (10(-6) M) promoted a vasorelaxant effect in a concentration-dependent manner and independent of vascular endothelium. A similar effect was obtained on KCl-induced pre-contractions (80 mM). (-)-Borneol (10(-5) -3 × 10(-4 ) M) inhibited contractions induced by cumulative addition of CaCl2 (10(-6) -3 × 10(-2) M) in depolarizing medium without Ca(2+) in a concentration-dependent manner. On S-(-) Bay K 8644-induced pre-contractions (10(-7) M), (-)-borneol did not induce significant changes compared with KCl-induced pre-contractions. In a Ca(2+) -free medium, (-)-borneol (10(-5) , 10(-4) or 10(-3) M) interfered in calcium mobilization from phenylephrine (10(-6) M)- or caffeine (20 mM)-sensitive intracellular stores. The involvement of K(+) channels was evaluated by tetraethylammonium (3 mM), 4-aminopyridine (1 mM) and glibenclamide (10(-5) M) pre-treatment, and (-)-borneol-induced vasorelaxation was markedly attenuated. Thus, this vasorelaxant effect can probably be attributed to calcium influx blockade through voltage-operated calcium channels (CaV L), calcium mobilization from intracellular stores and potassium channels activation.

Characterisation of the anti-inflammatory and antinociceptive activities and the mechanism of the action of Lippia gracilis essential oil.

ETHNOPHARMACOLOGICAL RELEVANCE: The species Lippia gracilis Schauer, known in Brazil as "Alecrim-da-chapada", is popularly used in folk medicine to treat cough, bronchitis, nasal congestion, and headache. MATERIALS AND METHODS: Lippia gracilis essential oil (EO; 10, 30, and 100mg/kg, p.o.) and the reference drugs morphine (5mg/kg, p.o.) and acetylsalicylic acid (ASA; 200mg/kg, p.o.) were evaluated using models for analgesia (acetic acid-induced contortion, formalin-induced licking, and hot plate) or inflammation (formalin-induced licking response and subcutaneous air pouch model). To elucidate the antinociceptive mechanism of action, animals were pre-treated with naloxone (opioid receptor antagonist; 1mg/kg, i.p.), atropine (cholinergic antagonist; 1mg/kg, i.p.) or l-nitro arginine methyl ester (L-NAME; 3mg/kg, i.p.) 30 min prior to oral administration of EO. RESULTS: EO significantly inhibited the number of writhings in acetic acid-induced contortions and the time that the animal spent licking the formalin-injected paw (second phase). All doses of EO increased the baseline and the area under the curve in the hot plate model. The administration of naloxone did not reverse the antinociceptive effect of EO in the acetic acid-induced contortion and formalin-induced licking models. L-NAME and atropine significantly reversed the effect of EO in the models of contortion, formalin, and hot plate. EO also inhibited the inflammatory process induced by subcutaneous carrageenan injection, reducing cell migration, exudate volume, extravased protein, and inflammatory mediators (nitric oxide, prostaglandin E2, TNF-α, and IFN-γ) produced in the pouch. CONCLUSIONS: Our results indicate that the essential oil from Lippia gracilis produces an antinociceptive effect that could be potentially mediated by cholinergic receptors and the nitric oxide pathway. Our data also suggest that the anti-inflammatory activity caused by EO exposure occurs through inhibition of nitric oxide and PGE2 production.

Characterisation of the anti-inflammatory and antinociceptive activities of the Hyptis pectinata (L.) Poit essential oil.

AIM OF THE STUDY: Hyptis pectinata Poit (Lamiaceae) is grown in the northeastern regions of Brazil and is popularly known as "sambacaitá" or "canudinho". It is extensively used in folk medicine to treat inflammatory conditions, bacterial infections, pain, and cancer. MATERIALS AND METHODS: Hyptis pectinata essential oil (EO, 10, 30, and 100mg/kg, p.o.) and the reference drugs morphine (5mg/kg, p.o.) and acetylsalicylic acid (ASA, 200mg/kg, p.o.) were evaluated using models for analgesia (acetic acid-induced contortions and hot plate) or inflammation (formalin-induced licking response and the subcutaneous air-pouch model). To elucidate the EO's mechanism of action, animals were pre-treated with the opioid receptor antagonist naloxone (1mg/kg, i.p.), the cholinergic antagonist atropine (1mg/kg, i.p.), or l-nitro arginine methyl ester (l-NAME, 3mg/kg, i.p.) 30 min prior to the oral administration of the EO. RESULTS: The EO significantly inhibited the number of writhings and the time the animals spent licking their formalin-injected paws (second phase). The EO, at doses of 30 and 100mg/kg, increased baseline measurements and area under the curve measurements in the hot plate model, respectively. The administration of naloxone reversed the antinociceptive effect of the EO in the hot plate model. l-NAME significantly reversed the effects of the EO in the contortions and hot plate models. Atropine completely reversed the antinociceptive activity of the EO in all models. Additionally, the EO inhibited the inflammatory process induced by subcutaneous carrageenan injection by reducing cell migration, exudate volume, protein concentration, and inflammatory mediators (nitric oxide, prostaglandin E2, IL-6, and TNF-α) produced in the pouch. CONCLUSIONS: Our results indicate that the Hyptis pectinata essential oil exhibits antinociceptive effects, likely mediated by opioid and cholinergic receptors, and anti-inflammatory activity through the inhibition of nitric oxide and PGE2 production.

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.

A study of the larvicidal activity of two Croton species from northeastern Brazil against Aedes aegypti.

The essential oils of Croton heliotropiifolius Kunth (Euphorbiaceae) and Croton pulegiodorus Baill. were selected for larvicidal evaluation against Aedes aegypti L. (Diptera: Culicidae) and studied qualitatively and quantitatively by GC and GC-MS. Sixty-one compounds representing 92.03% (C. heliotropiifolius) and 85.68% (C. pulegiodorus) of the essential oils, respectively, have been identified. The major components of C. heliotropiifolius essential oil were identified as beta-caryophyllene (35.82%), bicyclogermacrene (19.98%), and germacrene-D (11.85%). The major components in C. pulegiodorus essential oil were identified as beta-caryophyllene (20.96%), bicyclogermacrene (16.89%), germacrene-D (10.55%), tau-cadinol (4.56%), and beta-copaen-4-alpha-ol (4.35%). The essential oil of C. pulegiodorus (LC50 159 ppm) was more effective against Ae. aegypti than that of C. heliotropiifolius (LC50 544 ppm). In order to verify whether the major compound of both essential oils is the active principle responsible for the larvicidal activity, beta-caryophyllene was purchased and its larvicidal potential was further evaluated. However, beta-caryophyllene (LC50 1038 ppm) showed weak larvicidal potency. Results of larvicidal evaluation suggest the existence of a synergistic effect of minor components in the essential oils.

Larvicidal activity of para-benzoquinones.

Plant products may be alternative sources of mosquito larval control agents, since they constitute a rich source of bioactive compounds that are biodegradable into nontoxic products. It has been reported that quinones and derivatives present toxic activity against mosquito larvae Aedes aegypti. Therefore, these facts led us to investigate the larvicidal potential of six structurally related para-benzoquinones against A. aegypti L. (Culicidae) larvae, the vector of dengue fever. All the para-benzoquinones were found to have larvicidal effect. The unsubstituted para-benzoquinone was the compound that exhibited the lowest potency, while 2-isopropyl-para-benzoquinone was the most bioactive. In general, the presence of alkyl groups results in more potent compounds. In addition, the number, position, and size of these groups modulate the potency of the compounds. The experimental results showed that by appropriate structural modification of para-benzoquinones, it may be possible to develop novel insecticidal compounds with potential use to control A. aegypti population.

Evidence of the mechanism of action of Erythrina velutina Willd (Fabaceae) leaves aqueous extract.

ETHNOPHARMACOLOGICAL RELEVANCE: Erythrina velutina is traditionally used for sleepiness, convulsions and nervous system excitation in Brazil. Although central effects have been reported for Erythrina velutina, little is known about its mechanism of action. AIM OF THE STUDY: To investigate the pharmacological evidences of mechanism of action of Erythrina velutina leaves aqueous extract (AE). MATERIALS AND METHODS: Terminal segments of the guinea-pig ileum (n=5-8) were mounted in an organ bath and isotonic contractions were recorded. Phytochemical screening was carried out on AE. RESULTS: AE (0.025-2.50 mg/ml) produced contractile response in the guinea-pig ileum, yielding typical concentration-response curves (EC50=0.63 mg/ml). Electrically evoked contractions were significantly increased in the presence of AE. AE-elicited contractions were significantly reduced by bicuculline, tetrodotoxin, atropine, verapamil or incubation in low calcium-high potassium solution. Atropine along with verapamil abolished AE contractile response. Alkaloids, catechins, steroids, flavonols, flavononols, flavonoids, phenols, saponins, tannins, triterpenoids, and xanthones were detected in AE. CONCLUSIONS: AE contains important constituents for pharmacological activities. AE-induced contractions seem to involve GABAA receptor activation, acetylcholine release, muscarinic receptor activation, augmentation of Ca2+ entry through L-type calcium channels, and calcium release from the intracellular stores. These findings provide further support for Erythrina velutina traditional uses.

Antinociceptive effect and acute toxicity of the Hyptis suaveolens leaves aqueous extract on mice.

The aqueous extract of Hyptis suaveolens leaves was studied for their antinociceptive property in chemical and thermal models of nociception in mice. Oral administration of the aqueous extract (100, 200, and 400 mg/kg) dose-dependently reduced the number of writhings induced by acetic acid, decreased the licking activity of the early phase in formalin test and increased the reaction time in hot-plate test. The antinociceptive effect was significantly antagonized by naloxone (3 mg/kg; i.p.). Preliminary acute toxicity study showed that no animal death with doses up to 5 g/kg (p.o.).

Antinociceptive effect and acute toxicity of the essential oil of Hyptis fruticosa in mice.

The essential oil of the Hyptis fruticosa leaves was analyzed by GC/MS and evaluated for antinociceptive property as well as acute toxicity in mice. The essential oil, at doses of 100, 200, and 400 mg/kg (s.c.), produced significant inhibition of acetic acid-induced writhing, but did not manifest a significant effect in hot-plate test. There was no acute toxicity at doses up to 5 g/kg. Bicyclogermacrene, 1,8-cineole, alpha-pinene, and beta-caryophyllene were the major compounds detected in the essential oil.

Efeito antinociceptivo e antiinflamatório do extrato aquoso da entrecasca de Coutarea hexandra Schum. (Rubiaceae) / Antinociceptive and anti-inflammatory properties of Coutarea hexandra barks aqueous extract Schum. (Rubiaceae)

No estado de Sergipe, o chá da entrecasca de Coutarea hexandra Shum. (Rubiaceae) é popularmente utilizado no combate à dor e à inflamação. Estes usos etnofarmacológicos vieram motivar os estudos sobre os efeitos antinociceptivo e antiinflamatório, bem como sobre a toxicidade aguda do extrato aquoso liofilizado da entrecasca de Coutarea hexandra. Doses orais do extrato aquoso significativamente reduziram as contorções abdominais induzidas por ácido acético, aumentaram o tempo de latência ao calor no teste da placa quente, reduziram o edema de pata induzido por carragenina e, na segunda fase do teste da formalina, também reduziram a resposta dos animais à formalina. O efeito detectado no teste da formalina não foi revertido por naloxona ou cafeína. Nos ensaios de toxicidade aguda, não foi observada a morte de nenhum animal até a dose de 5 g/kg. Em conclusão, o extrato aquoso da entrecasca de C. hexandra possui efeitos antiinflamatório e antinociceptivo e não apresenta toxicidade aguda em camundongos. O efeito antinociceptivo não está relacionado à ativação dos sistemas opióide e adenosina e, ao menos parcialmente, é decorrente da atuação do extrato aquoso em nível central.

The aqueous extract of Coutarea hexandra Shum. (Rubiaceae) is extensively used on local folk medicine as anti-inflammatory and antinociceptive. In view of these facts, it was of our interest to evaluate the anti-inflammatory and antinociceptive activities. Its acute toxicity was also evaluated. The aqueous extract of Coutarea hexandra reduced acetic acid-induced writhing, increased the latency in the hot plate test, and reduced the second phase nociceptive response in the formalin test. Neither naloxone nor caffeine reversed aqueous extract of Coutarea hexandra effect in the second phase of the formalin test. The aqueous extract of Coutarea hexandra also reduced the rat paw edema induced by carrageenan. There was no animal death with doses up to 5 g/kg in the acute toxicity assays. These results showed that aqueous extract of C. hexandra has low acute toxicity, as well as, anti-inflammatory and antinociceptive effects, substantiating its popular usage. The antinociceptive effect seems to involve a central component, although it is not directly related to the opioid and adenosine systems.