Antinociceptive properties of caffeic acid derivatives in mice

UPLC-QTOF-MS/MS-based metabolomic approach and gastroprotective effect of two chemotypes of Egletes viscosa (L.) less. against ethanol-induced gastric ulcer in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Egletes viscosa (L.) (macela) is a native wild herb that can be found in different states of northeastern Brazil. The infusions of its flower buds are traditionally used for the treatment of gastrointestinal disorders. E. viscosa possesses two chemotypes (named A and B), distinguishable by the composition of the essential oil from the flower buds. Although there are previous studies of the gastroprotective effect of the isolated constituents of E. viscosa, its infusions have not been investigated yet.

AIM OF THE STUDY

The present study aimed to evaluate and compare the chemical composition and the gastroprotective effect of flower bud infusions of E. viscosa from chemotype A (EVCA) and chemotype B (EVCB).

MATERIALS AND METHODS

Sixteen infusions were brewed with flower buds according to the traditional preparation mode and were analyzed through a UPLC-QTOF-MS/MS based metabolomic approach for determination of their metabolic fingerprints and quantification of bioactive compounds. Afterward, these data were analyzed by chemometric methods (OPLS-DA) for discrimination of the two chemotypes. Additionally, infusions of EVCA and EVCB (50, 100 and 200 mg/kg, p.o.) were evaluated on gastric ulcers induced by absolute ethanol (96%, 0.2 mL, p.o.) in mice. To elucidate the gastroprotective mechanisms, the effect of EVCA and EVCB on gastric acid secretion and gastric wall mucus was determined and the role of TRPV1 channels, prostaglandins, nitric oxide and K_ATP channels were assessed. Moreover, the oxidative stress-related parameters and the histological aspects of the stomach tissue were analyzed.

RESULTS

The chemotypes can be discriminated from each other using UPLC-QTOF-MS/MS chemical fingerprints. Both chemotypes presented similar chemical compositions, consisting basically of caffeic acid derivatives, flavonoids and diterpenes. The quantification of bioactive compounds demonstrated that chemotype A possesses more ternatin, tanabalin and centipedic than chemotype B. EVCA and EVCB (50, 100 and 200 mg/kg, p.o.) significantly decreased the severity of ethanol-induced gastric lesions, as shown by a reduction in histological alterations and leucocyte infiltration in gastric tissue. The gastroprotective mechanism of both infusions involves an antioxidant effect, maintenance of gastric mucus and reduction gastric secretion. Stimulation of endogenous prostaglandins and nitric oxide release, activation of TRPV1 channels, and K_ATP channels are also involved in the gastroprotection of the infusions.

CONCLUSION

The gastroprotective effect of EVCA and EVCB was equivalent and mediated through antioxidant and antisecretory actions, including the activation of TRPV1 receptors, stimulation of endogenous prostaglandins and nitric oxide, and opening of K_ATP channels. The presence of caffeic acid derivatives, flavonoids and diterpenes in both infusions is involved in mediating this protective effect. Our findings support the traditional use of infusions of E. viscosa for gastric disorders regardless of the chemotype.

Oral Pharmacokinetics of Hydroxycinnamic Acids: An Updated Review

Hydroxycinnamic acids (HCAs) such as caffeic acid (CA), chlorogenic acid (CGA), coumaric acid (COA) isomers, ferulic acid (FA) and rosmarinic acid (RA) are natural phenolic acids with widespread distribution in vegetal foods and well-documented pharmacological activities. However, the low bioavailability of HCAs impairs their administration by the oral route. The present review addresses new findings and important factors/obstacles for their oral administration, which were unexplored in the reviews published a decade ago concerning the bioavailability of phenolic acids. Based on this, the article aims to perform an updated review of the water solubility and gastrointestinal stability of HCAs, as well as describe their oral absorption, distribution, metabolism and excretion (ADME) processes by in vitro, ex vivo, in situ and in vivo methods.

Ethnobotanical and phytochemical aspects of the edible herb Coriandrum sativum L

Coriandrum sativum (coriander) is an edible herb in the family Apiaceae. The leaves, fruits, and stems of C. sativum have long been used as culinary spice due to their favorable odor. Traditional practitioners used this plant for treating different diseases like blepharitis, scabies, aphthous stomatitis, laryngitis, headache, and palpitation. In modern researches, coriander has demonstrated anxiolytic, anticonvulsant, antimigraine, neuroprotective, analgesic, diuretic, hypoglycemic, hypolipidemic, hypotensive, anticancer, and antioxidant activities. Coriander contains a wide range of bioactive phytochemicals among which phenylpropenes, terpenoids, isocoumarins, phytosterols, and fatty acids are the most important. This review provides information about the botanical and ethnobotanical aspects, chemical profile, therapeutic uses in Islamic traditional medicine (ITM), and recent pharmacological studies of coriander effects. The results have shown that coriander and its monoterpenoid compound, linalool, can be considered as potential drug candidates for treating metabolic syndrome and different inflammatory conditions especially neural and CNS diseases.

Methanol Extract of Dicranopteris linearis Leaves Attenuate Pain via the Modulation of Opioid/NO-Mediated Pathway

Dicranopteris linearis leaf has been reported to exert antinociceptive activity. The present study elucidates the possible mechanisms of antinociception modulated by the methanol extract of D. linearis leaves (MEDL) using various mouse models. The extract (25, 150, and 300 mg/kg) was administered orally to mice for 30 min priot to subjection to the acetic acid-induced writhing-, hot plate- or formalin-test to establish the antinociceptive profile of MEDL. The most effective dose was then used in the elucidation of possible mechanisms of action stage. The extract was also subjected to the phytochemical analyses. The results confirmed that MEDL exerted significant (p < 0.05) antinociceptive activity in those pain models as well as the capsaicin-, glutamate-, bradykinin- and phorbol 12-myristate 13-acetate (PMA)-induced paw licking model. Pretreatment with naloxone (a non-selective opioid antagonist) significantly (p < 0.05) reversed MEDL effect on thermal nociception. Only l-arginine (a nitric oxide (NO) donor) but not N(ω)-nitro-l-arginine methyl ester (l-NAME; a NO inhibitor) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; a specific soluble guanylyl cyclase inhibitor) significantly (p < 0.05) modified MEDL effect on the writhing test. Several polyphenolics and volatile antinociceptive compounds were detected in MEDL. In conclusion, MEDL exerted the opioid/NO-mediated antinociceptive activity, thus, justify D. linearis as a potential source for new analgesic agents development.

Caffeates and Caffeamides: Synthetic Methodologies and Their Antioxidant Properties

Polyphenols are secondary metabolites of plants and include a variety of chemical structures, from simple molecules such as phenolic acids to condensed tannins and highly polymerized compounds. Caffeic acid (3,4-dihydroxycinnamic acid) is one of the hydroxycinnamate metabolites more widely distributed in plant tissues. It is present in many food sources, including coffee drinks, blueberries, apples, and cider, and also in several medications of popular use, mainly those based on propolis. Its derivatives are also known to possess anti-inflammatory, antioxidant, antitumor, and antibacterial activities, and can contribute to the prevention of atherosclerosis and other cardiovascular diseases. This review is an overview of the available information about the chemical synthesis and antioxidant activity of caffeic acid derivatives. Considering the relevance of these compounds in human health, many of them have been the focus of reviews, taking as a center their obtaining from the plants. There are few revisions that compile the chemical synthesis methods, in this way, we consider that this review does an important contribution.

Isopropyl Caffeate: A Caffeic Acid Derivative-Antioxidant Potential and Toxicity

Phenolic compounds, among them isopropyl caffeate, possess antioxidant potential, but not without toxicity and/or adverse effects. The present study aimed to evaluate the antioxidant activity and toxicity of isopropyl caffeate through in silico, in vitro and in vivo testing. The results showed that isopropyl caffeate presents no significant theoretical risk of toxicity, with likely moderate bioactivity: GPCR binding, ion channel modulation, nuclear receptor binding, and enzyme inhibition. Isopropyl caffeate induced hemolysis only at the concentrations of 500 and 1000 μg/ml. We observed types A and O erythrocyte protection from osmotic stress, no oxidation of erythrocytes, and even sequestrator and antioxidant behavior. However, moderate toxicity, according to the classification of GHS, was demonstrated through depressant effects on the central nervous system, though there was no influence on water and food consumption or on weight gain, and it did present possible hepatoprotection. We conclude that the effects induced by isopropyl caffeate are due to its antioxidant activity, capable of preventing production of free radicals and oxidative stress, a promising molecule with pharmacological potential.

Coriander (Coriandrum sativum): A promising functional food toward the well-being

Coriandrum sativum (C. sativum) or coriander is one of the most popularly used spices in culinary worldwide, and its medicinal values has been recognized since ancient time. C. sativum contains bioactive phytochemicals that are accounted for a wide range of biological activities including antioxidant, anticancer, neuroprotective, anxiolytic, anticonvulsant, analgesic, migraine-relieving, hypolipidemic, hypoglycemic, hypotensive, antimicrobial, and antiinflammatory activities. The major compound, linalool, abundantly found in seeds is remarked for its abilities to modulate many key pathogenesis pathways of diseases. Apart from the modulating effects, the potent antioxidant property of the C. sativum provides a key mechanism behind its protective effects against neurodegenerative diseases, cancer, and metabolic syndrome. This review shed light on comprehensive aspects regarding the therapeutic values of the C. sativum, which indicate its significance of being a promising functional food for promoting the well-being in the era of aging and lifestyle-related diseases.

Phytochemical profile and mechanisms involved in the anti-nociception caused by the hydroethanolic extract obtained from Tocoyena formosa (Cham. & Schltdl.) K. Schum (Jenipapo-bravo) leaves in mice

Tocoyena formosa, a small ornamental tree growing in the dry regions of central Brazil, is commonly known as 'genipapo do bravo'. This is a medicinal plant traditionally used as an analgesic for rheumatic pain, lower back pain and myalgia, however its use is carried out without scientific evidence, which thus justifies the development of studies to investigate and prove its therapeutic potential. Therefore, the objective of this study was to evaluate the phytochemical profile of Tocoyena formosa (Cham. & Schlecht.) K. Schum (TFLHE) and the mechanisms involved in its anti-nociceptive effect. The TFLHE revealed the presence of gallic acid, catechin, chlorogenic acid, caffeic acid, ellagic acid, rutin, quercetin and luteolin. The TFLHE at doses of 200 and 400mg/kg significantly decreased acetic acid-induced abdominal contortions, the reaction time for the formalin test in both phases and increased the paw withdrawal time in the hot plate thermal stimulus test. The 200mg/kg dose also significantly inhibited the plantar mechanical hyperalgesia intensity induced by formalin within 24h.

TREATMENT

with the TFLHE did not cause significant changes in motor performance and coordination in the Rota Rod test. The investigation on the possible mechanism of antinociceptive action of TFLHE indicates the involvement of opioid, glutamatergic, nitric oxide/cGMP and vanilloid systems. It is concluded that the TFLHE has an antinociceptive effect promoted by the aforementioned mechanisms.

APA-style human milk fat analogue from silkworm pupae oil: Enzymatic production and improving storage stability using alkyl caffeates

Silkworm pupae oil derived from reeling waste is a rich source of α-linolenic acid (ALA), which has multipal applications. ALAs were added in sn-1, 3 positions in a triacylglycerol (TAG) to produce an APA-human milk fat analogues (APA-HMFAs, A: α-linolenic acid, P: palmitic acid). The optimum condition is that tripalmitin to free fatty acids of 1:12 (mole ratio) at 65 °C for 48 h using lipase Lipozyme RM IM. Results show that, the major TAG species that comprised APA-HMFAs were rich in ALA and palmitic acid, which contained 64.52% total unsaturated fatty acids (UFAs) and 97.05% PA at the sn-2 position. The melting point of APA was −27.5 °C which is much lower than tripalmitin (40.5 °C) indicating more plastic character. In addition, the practical application of alkyl caffeates as liposoluble antioxidants in APA was developed. Alkyl caffeate showed a superior IC₅₀ (1.25–1.66 μg/mL) compared to butyl hydroxy anisd (1.67 μg/mL) and L-ascorbic acid-6-palmitate (L-AP) (1.87 μg/mL) in DPPH analysis. The addition of ethyl caffeate to oil achieved a higher UFAs content (73.58%) at high temperatures. Overall, APA was obtained from silkworm pupae oil successfully, and the addition of caffeates extended storage ranges for APA-HMFAs.

Caffeic acid exhibits anti-pruritic effects by inhibition of multiple itch transmission pathways in mice

Itch is an unpleasant sensation that evokes a desire to scratch. Although often regarded as a trivial 'alarming' sensation, itch may be debilitating and exhausting, leading to reduction in quality of life. In the current study, the question of whether caffeic acid can be used to alleviate itch sensation induced by various pruritic agents, including histamine, chloroquine, SLIGRL-NH2, and β-alanine was investigated. It turned out that histamine-induced intracellular calcium increase was significantly blocked by caffeic acid in HEK293T cells that express H1R and TRPV1, molecules required for transmission of histamine-induced itch in sensory neurons. In addition, inhibition of histamine-induced intracellular calcium increase by caffeic acid was demonstrated in primary cultures of mouse dorsal root ganglion (DRG). When chloroquine, an anti-malaria agent known to induce histamine-independent itch - was used, it was also found that caffeic acid inhibits the induced response in both DRG and HEK293T cells that express MRGPRA3 and TRPA1, underlying molecular entities responsible for chloroquine-mediated itch. Likewise, intracellular calcium changes by SLIGRL-NH2 - an itch-inducing agent via PAR2 and MRGPRC11 - were decreased by caffeic acid as well. However, it was found that caffeic acid is not capable of inhibiting β-alanine-induced responses via its specific receptor MRGPRD. Finally, in vivo scratching behavior tests showed that caffeic acid indeed has anti-scratching effects against histamine, chloroquine, and SLIGRL-NH2 administration but not by β-alanine. Overall, the current study demonstrated that caffeic acid has anti-itch effects by inhibition of multiple itch mechanisms induced by histamine, chloroquine and SLIGRL-NH2.

Bioactive Metabolites from Cnidoscolus souzae and Acmella pilosa

The bioassay-guided purification of the ethanol extracts of Acmella pilosa and Cnidoscolus souzae, two plants of the native flora of the Yucatan Peninsula used in traditional medicine to treat inflammation and pain, resulted in the identification of rosmarinic acid (1) and caffeic acid (2) as the bioactive metabolites from A. pilosa, and of 7-deoxynimbidiol (4) as the major bioactive metabolite from C. souzae. Metabolites 1, 2, and 4 proved to be responsible for the antioxidant activity originally detected in the corresponding organic crude extracts; 7-deoxynimbidiol (4) showed good analgesic and anti-inflammatory activities, inhibiting the pain induced by PGE2 and reducing the edema induced by carrageenan, respectively.

N-Phenethyl caffeamide and photodamage: protecting skin by inhibiting type I procollagen degradation and stimulating collagen synthesis

Skin is mainly damaged by genetic and environmental factors such as ultraviolet (UV) light and pollutants. UV light is a well-known factor that causes various types of skin damage and premature aging. Reactive oxygen species (ROS) are commonly involved in the pathogenesis of skin damage by activating the metalloproteinases that break down type I collagen. This study investigated the antioxidant and antiphotodamage activity and mechanisms of N-phenethyl caffeamide (K36) in human skin fibroblasts. The results indicated that K36 demonstrated strong 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging activity, which dose-dependently reduced the production of UVB-induced intracellular ROS in human dermal fibroblasts. K36 prevented UVB-irradiation-induced type I collagen degradation by inhibiting the expression of matrix metalloproteins-1, -3, and -9 and the phosphorylation of mitogen-activated protein (MAP) kinases. Furthermore, K36 elevated collagen synthesis in skin fibroblasts by inhibiting UVB-induced Smad7 overexpression. K36 downregulated the expression of the transcription factor, activator protein-1 (AP-1). Our results indicated that K36 exhibited antioxidant properties and prevented skin collagen degradation caused by UV exposure and the stimulation of collagen synthesis, which suggests the potential use of K36 in preventing photodamage.

Alkyl caffeates improve the antioxidant activity, antitumor property and oxidation stability of edible oil

Caffeic acid (CA) is distributed widely in nature and possesses strong antioxidant activity. However, CA has lower solubility in non-polar media, which limits its application in fat-soluble food. To increase the lipophilicity of natural antioxidant CA, a series of alkyl caffeates were synthesized and their antioxidant and antitumor activities were investigated. The antioxidant parameters, including the induction period, acid value and unsaturated fatty acid content, of the alkyl caffeates in edible oil were firstly investigated. The results indicated that alkyl caffeates had a lower DPPH IC₅₀ (14–23 µM) compared to CA, dibutyl hydroxy toluene (BHT) and Vitamin C (24–51 µM), and significantly inhibited four human cancer cells (SW620, SW480, SGC7901 and HepG2) with inhibition ratio of 71.4–78.0% by a MTT assay. With regard to the induction period and acid value assays, methyl and butyl caffeates had higher abilities than BHT to restrain the oxidation process and improve the stability of edible oil. The addition of ethyl caffeate to oil allowed maintenance of a higher unsaturated fatty acid methyl ester content (68.53%) at high temperatures. Overall, the alkyl caffeats with short chain length (n<5) assessed better oxidative stability than those with long chain length. To date, this is the first report to the correlations among the antioxidant activity, anticancer activity and oxidative stability of alkyl caffeates.

Rapid synthesis of propyl caffeate in ionic liquid using a packed bed enzyme microreactor under continuous-flow conditions

Propyl caffeate has the highest antioxidant activity among caffeic acid alkyl esters, but its industrial production via enzymatic transesterification in batch reactors is hindered by a long reaction time (24h). To develop a rapid process for the production of propyl caffeate in high yield, a continuous-flow microreactor composed of a two-piece PDMS in a sandwich-like microchannel structure was designed for the transesterification of methyl caffeate and 1-propanol catalyzed by Novozym 435 in [B mim][CF3SO3]. The maximum yield (99.5%) in the microreactor was achieved in a short period of time (2.5h) with a flow rate of 2 μL/min, which kinetic constant Km was 16 times lower than that of a batch reactor. The results indicated that the use of a continuous-flow packed bed enzyme microreactor is an efficient method of producing propyl caffeate with an overall yield of 84.0%.

Chemical composition and antinociceptive, anti-inflammatory and antiviral activities of Gallesia gorazema (Phytolaccaceae), a potential candidate for novel anti-herpetic phytomedicines

ETHNOPHARMACOLOGICAL RELEVANCE

In traditional medicine, teas made from leaves and bark of Gallesia gorazema are used as antispasmodic, anthelmintic, antihemorrhagic and febrifuge agents. Crude leaves of this plant are also employed as a remedy in the treatment of abscesses, orchitis, gonorrhea and for rheumatic pain relief. this study investigates the presumed antinociceptive and anti-inflammatory activities of leaves and roots Gallesia gorazema (Phytolaccaceae) extracts. The most active extract and its isolated compound, a new natural product, are also evaluated against viruses HSV-1 and HSV-2.

MATERIALS AND METHODS

In vivo experiments with mice were used to assess the analgesic and anti-inflammatory activities of Gallesia gorazema extracts. Antiviral activity of extracts and the new natural product was investigated by in vitro experiments.

RESULTS

Results show that dichloromethanic root (DRE) and ethanolic leaf (ELE) extracts displayed significant antinociceptive and anti-inflammatory activities in in vivo experiments with mice. Both extracts were also assayed against the herpes simplex viruses HSV-1 and HSV-2, but only DRE was highly active, showing a selective antiviral effect against HSV-1. Phytochemical fractionation of DRE led to the isolation of 28-hydroxyoctacosyl ferulate, a novel natural product, which displayed strong antiviral activity against HSV-1 (EC₅₀=21.6 μg/mL) with a selective index above 9, justifying, at least in part, the high selective antiviral activity observed for DRE.

CONCLUSION

These results suggest that the plant Gallesia gorazema is a potential candidate for the development of novel anti-herpetic phytomedicines.

A novel chemoenzymatic synthesis of propyl caffeate using lipase-catalyzed transesterification in ionic liquid

Propyl caffeate has the highest antioxidant capacity in the caffeate alkyl esters family, but industrial production of propyl caffeate is hindered by low yields using either the chemical or enzymatic catalysis method. To set up a high-yield process for obtaining propyl caffeate, a novel chemoenzymatic synthesis method using lipase-catalyzed transesterification of an intermediate methyl caffeate or ethyl caffeate and 1-propanol in ionic liquid was established. The maximum propyl caffeate yield of 98.5% was obtained using lipase-catalyzed transesterification under the following optimal conditions: Novozym 435 as a biocatalyst, [Bmim][CF3SO3] as a medium, a molar ratio of methyl caffeate to 1-propanol of 1:5, a mass ratio of methyl caffeate to lipase of 1:20, and a reaction temperature of 60°C. The two-step conversion of caffeic acid to propyl caffeate via methyl caffeate is an efficient way to prepare propyl caffeate with an overall yield of 82.7%.

Antinociceptive activity of aqueous extract and isolated compounds of Lithrea molleoides

ETHNOPHARMACOLOGICAL RELEVANCE

Lithrea molleoides (Vell.) Engl. (Anacardiaceae) is a medicinal plant commonly used in traditional medicine in South America.

AIM OF THE STUDY

In the present study, the in vivo antinociceptive effect of L. molleoides' aqueous extract and its isolated compounds has been investigated.

MATERIALS AND METHODS

Antinociceptive activity was evaluated through writhing, formalin and hot plate tests in mice. The phytochemical analysis was performed.

RESULTS

The extract produced significant inhibition on nociception induced by acetic acid (ED50: 8.7 mg/kg, i.p.) and formalin (ED50: 7.7 mg/kg, i.p.) administered intraperitoneally and also orally. Yohimbine diminished the activity of the extract in the acetic acid test meanwhile haloperidol enhanced its effect. Two majority compounds, shikimic and vanillic acid were active in chemical nociceptive models used in this work, producing the highest inhibition of the writhing response at a dose of 30 mg/kg i.p. (55.4% and 57.1%, respectively) meanwhile at 100 mg/kg p.o. produced a slight response (23.3% and 23.9%, respectively).

CONCLUSIONS

These results suggest that L. molleoides' aqueous extract produced antinociception possibly related to the presence of shikimic and vanillic acid. The adrenergic and dopaminergic systems seem to be involved in the mechanism of antinociception of the extract.

Hexyl (E)-3-(3,4-dihy-droxy-phen-yl)acrylate

The title mol­ecule, C₁₅H₂₀O₄, has an E conformation about its C=C bond and is almost planar (r.m.s. deviation of all non-H atoms = 0.04 Å). The crystal structurere features O—H⋯O and C—H⋯O hydrogen bonds.

Pentyl (E)-3-(3,4-dihy-droxy-phen-yl)acrylate

In the mol­ecule of the title compound, C₁₄H₁₈O₄, the C=C double bond is in an E configuration. The mol­ecule is almost planar (r.m.s. deviation of all non-H atoms = 0.04 Å). An intra­molecular O—H⋯O hydrogen bond occurs. In the crystal, inter­molecular O—H⋯O inter­actions link the mol­ecules into ribbons extending in [110].

Antinociceptive activity of ethanolic extract and isolated compounds of Urtica circularis

ETHNOPHARMACOLOGICAL RELEVANCE

Urtica circularis (Hicken) Sorarú is a medicinal plant commonly used in traditional medicine to relieve pain in inflammatory processes.

AIM OF THE STUDY

In the present study, the in vivo antinociceptive effect of Urtica circularis ethanolic extract and its isolated compounds has been investigated.

MATERIALS AND METHODS

Antinociceptive activity was evaluated through writhing, formalin and hot plate tests in mice. The phytochemical analysis was performed.

RESULTS

The extract produced significant inhibition on nociception induced by acetic acid (ED50: 72.2mg/kg, i.p.) and formalin (ED50: 15.8 mg/kg, i.p.) administered intraperitoneally and also orally. Atropine diminished the activity of the extract in the acetic acid test. In this model, at dose of 10mg/kg i.p., vitexin was the most active of the isolated compounds (inhibition of 91%), and chlorogenic acid, caffeic acid and vicenin-2 (6,8-di-C-glucosyl apigenin) produced an inhibition of 72%, 41% and 41%, respectively, whereas apigenin did not show any activity.

CONCLUSIONS

These results suggest that Urtica circularis extract produced antinociception possibly related to the presence of vitexin, chlorogenic, caffeic acid and vicenin-2. The activation of cholinergic systems seems to be involved in the mechanism of antinociception of the extract.

(E)-Isopropyl 3-(3,4-dihy-droxy-phen-yl)acrylate

In the title compound, C(12)H(14)O(4), a derivative of caffeic acid [(E)-3-(3,4-dihy-droxy-phen-yl)-2-propenoic acid], an intra-molecular O-H⋯O hydrogen bond forms an S(5) ring. In the crystal, inter-molecular O-H⋯O hydrogen bonds link mol-ecules into chains propagating in [110].

Olive (Olea europaea L.) leaf extract elicits antinociceptive activity, potentiates morphine analgesia and suppresses morphine hyperalgesia in rats

AIM OF THE STUDY

Olive (Olea europaea) leaves are used as anti-rheumatic, anti-inflammatory, antinociceptive, antipyretic, vasodilatory, hypotensive, antidiuretic and hypoglycemic agents in traditional medicine. Recently, it has been shown that olive leaf extract (OLE) has calcium channel blocker property; however, its influences on nociceptive threshold and morphine effects have not yet been clarified.

MATERIALS AND METHODS

All experiments were carried out on male Wistar rats. The tail-flick, hot-plate and formalin tests were used to assess the effect of OLE on nociceptive threshold. To determine the effect of OLE on analgesic and hyperalgesic effects of morphine, OLE (6, 12 and 25 mg/kg i.p.) that had no significant nociceptive effect, was injected concomitant with morphine (5 mg/kg and 1 μg/kg i.p., respectively). The tail-flick test was used to assess the effect of OLE on anti- and pro-nociceptive effects of morphine.

RESULTS

The data showed that OLE (50-200 mg/kg i.p.) could produce dose-dependent analgesic effect on tail-flick and hot-plate tests. Administration of 200 mg/kg OLE (i.p.) caused significant decrease in pain responses in the first and the second phases of formalin test. In addition, OLE could potentiate the antinociceptive effect of 5 mg/kg morphine and block low-dose morphine-induced hyperalgesia.

CONCLUSION

Our results indicate that olive leaf extract has analgesic property in several models of pain and useful influence on morphine analgesia in rats. Therefore, it can be used for the treatment and/or management of painful conditions.