Anti-Inflammatory Properties and Chemical Characterization of the Essential Oils of Four Citrus Species.

Citrus fruits have potential health-promoting properties and their essential oils have long been used in several applications. Due to biological effects described to some citrus species in this study our objectives were to analyze and compare the phytochemical composition and evaluate the anti-inflammatory effect of essential oils (EO) obtained from four different Citrus species. Mice were treated with EO obtained from C. limon, C. latifolia, C. aurantifolia or C. limonia (10 to 100 mg/kg, p.o.) and their anti-inflammatory effects were evaluated in chemical induced inflammation (formalin-induced licking response) and carrageenan-induced inflammation in the subcutaneous air pouch model. A possible antinociceptive effect was evaluated in the hot plate model. Phytochemical analyses indicated the presence of geranial, limonene, γ-terpinene and others. EOs from C. limon, C. aurantifolia and C. limonia exhibited anti-inflammatory effects by reducing cell migration, cytokine production and protein extravasation induced by carrageenan. These effects were also obtained with similar amounts of pure limonene. It was also observed that C. aurantifolia induced myelotoxicity in mice. Anti-inflammatory effect of C. limon and C. limonia is probably due to their large quantities of limonene, while the myelotoxicity observed with C. aurantifolia is most likely due to the high concentration of citral. Our results indicate that these EOs from C. limon, C. aurantifolia and C. limonia have a significant anti-inflammatory effect; however, care should be taken with C. aurantifolia.

Anti-inflammatory activity of Choisya ternata Kunth essential oil, ternanthranin, and its two synthetic analogs (methyl and propyl N-methylanthranilates).

Choisya ternata Kunth (Rutaceae) is native to North America where it is popularly known as "Mexican orange". In this study, the anti-inflammatory effects of the essential oil (EO) obtained from the leaves of C. ternata, one of its minor components (ternanthranin-ISOAN) and its two synthetic analogues (methyl and propyl N-methylanthranilate--MAN and PAN) were evaluated. Mice pretreated with the EO (EO) obtained from C. ternata leaves (3-100 mg/kg, p.o.), ISOAN, MAN or PAN (1-30 mg/kg, p.o.) and the reference drugs, morphine (1 mg/kg, p.o.) and acetylsalicylic acid (ASA, 100 mg/kg, p.o.), were evaluated in inflammation models such as formalin and subcutaneous air pouch models, with measurement of cell migration, exudate volume, protein extravasation, nitric oxide and pro-inflammatory cytokines. The EO from C. ternata significantly inhibited the time that the animals spent licking the formalin-injected paw in the second phase of the model at their higher doses (30 and 100 mg/kg, respectively). An inhibition of the inflammatory reaction induced after subcutaneous carrageenan injection into air pouch was also observed. In this model, the EO significantly reduced cell migration, exudate volume, protein extravased, and the increase in levels of inflammatory mediators (nitric oxide, TNF-α and IL-1ß). ISOAN, MAN and PAN behaved in the same fashion at much smaller doses. Also, these molecules were able to show significant effects in the reduction of paw edema (at all tested doses) when the phlogistic agent was carrageenan, bradykinin, 5-HT, PGE2, C48/80 or 12-O-tetradecanoylphorbol-acetate (TPA). None of the tested doses had any effect in reducing histamine-induced edema. Our results indicate that the EO from C. ternata and anthranilate derivatives demonstrates an anti-inflammatory effect.

Antinociceptive esters of N-methylanthranilic acid: Mechanism of action in heat-mediated pain.

Recently, we identified a new natural antinociceptive alkaloid ternanthranin, isopropyl N-methylanthranilate (ISOAN), from the plant species Choisya ternata Kunth (Rutaceae). In this work we concentrated on the elucidation of its mechanism of action in comparison with two other esters of this acid (methyl (MAN) and propyl (PAN)). Mice orally pre-treated with ISOAN, MAN or PAN (at 0.3, 1 and 3mg/kg) were less sensitive to chemical or thermal stimuli in different nociception models (formalin-, capsaicin- and glutamate-induced licking response, tail flick and hot plate). All compounds (1 and 3mg/kg) showed significant activity in the peripheral nociception models, as well as a dose-dependent spinal antinociceptive effect in the tail flick model. We observed that glibenclamide was able to reverse the antinociceptive effect of ISOAN in the hot plate model suggesting the involvement of K(+)ATP channels. The antinociceptive effect of MAN and PAN may be related to adrenergic, nitrergic and serotoninergic pathways. In addition, the antinociception of PAN was reverted by naloxone implying that the opioid pathway participates in its activity. The cholinergic and cannabinoid systems were found not be involved in the onset of the antinociceptive effects of any of the esters. In conclusion, isopropyl, methyl and propyl N-methylanthranilates produced significant peripheral and central antinociception at doses lower than that of morphine, the classical opioid analgesic drug, without causing toxicity.

Antinociceptive effect of the Orbignya speciosa Mart. (Babassu) leaves: evidence for the involvement of apigenin.

AIMS: Babassu is the common Brazilian name of Orbignya speciosa Mart. (Arecaceae). The fruits are used for several disorders. In the present study, the antinociceptive effects of the ethanol extract (EE) and dichloromethane fraction (DF) obtained from leaves were investigated, as well as apigenin using nociception models (acetic acid-induced abdominal writhing, formalin, and hot plate). MAIN METHODS: Mice were treated with EE, DF (10, 30, and 100mg/kg, p.o.), apigenin (1mg/kg, p.o.), morphine (5mg/kg, s.c.), acetylsalicylic acid (100mg/kg, p.o.) or vehicle (0.1 ml, p.o.). The EE and DF reduced the contortions induced by acetic acid. Both also reduced the licking response in the formalin model. In the hot plate model, the antinociceptive effects were, at least, equal to that shown by morphine. To elucidate the antinociceptive mechanism of action of EE, DF, and apigenin the animals were pre-treated with atropine (nonselective muscarinic receptor antagonist, 1mg/kg, s.c.), naloxone (opioid receptor antagonist, 1mg/kg, s.c.), l-nitro arginine methyl ester (L-NAME, nitric oxide synthase inhibitor, 3mg/kg, s.c.) or mecamylamine (nicotinic receptor antagonist, 2mg/kg, s.c.) and evaluated in the hot plate model. KEY FINDINGS: The antinociception produced by DF was abolished by atropine, naloxone or mecamylamine. The effect of apigenin was significantly blocked by atropine or naloxone. SIGNIFICANCE: The results obtained indicated that EE and DF have antinociceptive activity that is mediated, at least in part, by opioid and cholinergic systems. This effect can be attributed to the presence of apigenin, a flavonoid in the dichloromethane fraction.

A novel toxic alkaloid from poison hemlock (Conium maculatum L., Apiaceae): identification, synthesis and antinociceptive activity.

2-Pentylpiperidine, named conmaculatin, a novel volatile alkaloid related to coniine was identified from the renowned toxic weed Conium maculatum L. (Apiaceae). The structure of conmaculatin was corroborated by synthesis (8 steps starting from cyclohexanol, overall yield 12%). Conmaculatin's strong peripheral and central antinociceptive activity in mice was observed in a narrow dose range (10-20mg/kg). It was found to be lethal in doses higher than 20mg/kg.

Identification of a new antinociceptive alkaloid isopropyl N-methylanthranilate from the essential oil of Choisya ternata Kunth.

ETHNOPHARMACOLOGICAL RELEVANCE: Mexican people employed infusion of leaves of Choisya ternata Kunth for their antispasmodic and "simulative properties". AIM OF THE STUDY: In the present study the detailed GC and GC-MS analyses of the essential oil of Choisya ternata Kunth (Rutaceae) were performed. The presence of a minor constituent isopropyl N-methylanthranilate (1) was revealed among other identified volatiles. A synthesis of 1 was undertaken in order to corroborate this find and obtain gram quantities that would allow the testing of its biological activity (peripheral and central antinociceptive activity). MATERIALS AND METHODS: The oils were investigated by GC and GC-MS. Synthesized compounds were spectrally characterized (UV-Vis, IR, 1D and 2D NMR, MS). The obtained synthetic samples of compounds were assayed for peripheral and central antinociceptive activity in two models (effects on acetic acid induced writhing in mice and the hot plate test for nociception). RESULTS: Detailed GC and GC-MS analyses of the essential oil of Choisya ternata Kunth (Rutaceae) among 157 other identified volatiles revealed the presence of a minor constituent isopropyl N-methylanthranilate (1). Compound 1, named ternanthranin, is therefore detected as a natural product for the first time with a very restricted occurrence (samples of several citrus oils were screened for the presence of 1). The antinociceptive activities were assayed for ternanthranin, the two other synthetic analogs, methyl and propyl N-methylanthranilate, as well as the essential oil and the crude ethanol extract of the leaves. The results clearly demonstrate a very high (even significant at 0.3 mg/kg) dose dependent activity for the anthranilates (and the extracts). Isopropyl N-methylanthranilate showed the highest, while methyl N-methylanthranilate showed the lowest activity (with the methyl ester at 3 mg/kg still better than acetylsalicylic acid, at 200 mg/kg, in the first, or comparable with morphine, at 5mg/kg, in the second test). CONCLUSION: This study once again revealed that detailed investigations of plant species with ethnopharmacologically documented activity may yield new natural compounds-a new alkaloid (ternanthranin), a volatile simple anthranilate that can be considered responsible for the antinociceptive activity of the crude plant extracts.