Journal of Ethnopharmacology 146 (2013) 318–323

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Anti-hyperalgesic activity of corilagin, a tannin isolated from Phyllanthusniruri L. (Euphorbiaceae)

Jeverson Moreira a, Luiz Carlos Klein-Junior a,b, Valdir Cechinel Filho a,b, Fatima de Campos Buzzi a,b,n

a Nucleo de Investigac- ~oes Quımico-Farmaceuticas—NIQFAR, Universidade do Vale do Itajaı-UNIVALI, 88.302-202, Itajaı, Santa Catarina, Brazilb Programa de Pos-Graduac- ~ao em Ciencias Farmaceuticas, Universidade do Vale do Itajaı-UNIVALI, 88.302-202, Itajaı, Santa Catarina, Brazil

a r t i c l e i n f o

Article history:

Received 25 August 2012

Received in revised form

17 December 2012

Accepted 27 December 2012Available online 17 January 2013

Keywords:

Corilagin

Antinociception

Phyllanthus niruru L.

41/$ - see front matter & 2013 Elsevier Irelan

x.doi.org/10.1016/j.jep.2012.12.052

esponding author at: Programa de Pos-Gra

s, Nucleo de Investigac- ~oes Quımico-Farmace

iversidade do Vale do Itajaı—UNIVALI, It

5 4733417855.

ail address: fcamposbuzzi@univali.br (F.d.C. B

a b s t r a c t

Ethnopharmacological relevance: Corilagin (b-1-O-galloyl-3,6-(R)-hexahydroxydiphenoyl-D-glucose) is a

tannin isolated from Phyllanthus niruri (Euphorbiaceae). This plant is well known for their therapeutic

purposes to treat several diseases associated with dolorous process and are used in several ethno-

medicines in tropical and subtropical countries.

Aim of the study: This study was designed to evaluate the anti-hyperalgesic activity of corilagin using

chemically and thermally based nociception models in mice.

Materials and methods: Corilagin was isolated from Phyllanthus niruri (Euphorbiaceae) by extraction

and chromatographic procedures and the anti-hyperalgesic activity was evaluated by using writhing,

formalin, capsaicin, glutamate and hot plate tests in mice.

Results: Corilagin presented activity in acetic acid model with the ID50 calculated value of 6.46 (3.09–

13.51) being about 20.6 fold more potent than acetylsalicylic acid. It also exhibited activity against the

first phase of formalin test with ID50 value of 18.38 (15.15–22.59) mmol/kg. In the capsaicin and

glutamate models, corilagin demonstrated significant activity at the 3 mg/kg.

Conclusion: The experimental data demonstrated that corilagin exhibits anti-hyperalgesic activity that

may be due to interaction with the glutamatergic system.

& 2013 Elsevier Ireland Ltd. All rights reserved.

1. Introduction

Phyllanthus niruri Linn., Euphorbiaceae, known in Brazil as‘‘quebra-pedra’’ and in other Latinoamerican countries as ‘‘chan-capiedra’’ occurs widely in the tropical and subtropical countries.Infusion of different parts of this plant and other from the genusPhyllanthus is frequently used with therapeutic purposes to treatseveral diseases particularly disturbances of kidney and urinarybladder associated with the dolorous process (Calixto et al., 1998;Khanna et al., 2002; Ranilla et al., 2010; Shanbhag et al., 2010).Experimental studies have confirmed different pharmacologicalproperties such as hepatoprotective (Harish and Shivanandappa,2006), antiplasmodial (Cimanga et al., 2004), antihyperlipemic(Khanna et al., 2002), antihyperuricemic (Murugaiyah and Chan,2009) and antioxidant activities (Sarkar et al., 2009). Moreover,there are quite a few studies reporting the antinociceptive effectof Phyllanthus niruri (Santos et al., 1994, 1995a, 1995b; Obidikeet al., 2010). The medicinal effects are attributed to the active

d Ltd. All rights reserved.

duac- ~ao em Ciencias Farm-

uticas—NIQFAR, Rua Uruguai

ajaı, Santa Catarina, Brazil.

uzzi).

components present in Phyllanthus niruri, such as lignans(Murugaiyah and Chan, 2007), flavonoids (Shakil et al., 2008),terpenoids (Singh et al., 1989) and in particular, tannins (Markomet al., 2007).

Corilagin (b-1-O-galloyl-3,6-(R)-hexahydroxydiphenoyl-D-glu-cose) (Fig. 1), a tannin isolated from several plants, includingPhyllanthus niruri, has also been used as a phytochemical markerfor qualitative and quantitative studies of this plant (Colomboet al., 2009). Some pharmacological activities of corilaginhave already been described, such as antiatherogenic (Duanet al., 2005), antioxidant (Chen and Chen, 2011), hepatoprotec-tive (Kinoshita et al., 2007) and anti-tumor (Hau et al., 2010).Furthermore, corilagin was also able to inhibit the release ofcytokines such as TNF-a, IL-1b and IL-6 as well as the produc-tion of nitric oxide, both of which are mediators of inflamma-tion and pain (Okabe et al., 2001; Zhao et al., 2008; Dong et al.,2010).

Considering that Phyllanthus niruri has already demonstratedantinociceptive activity in vivo and, that one of the main constituentsof the species is corilagin, which was able to inhibit mediators relatedto inflammatory pain; and since there is no study evaluating theantinociceptive properties of the tannin, this study assesses the effectsof corilagin treatment on chemically and thermally based nociceptionmodels in mice.

Fig. 1. Chemical structure of corilagin (b-1-O-galloyl-3,6-(R)-hexahydroxydiphe-

noyl -D-glucose).

Table 113C NMR chemical shifts for corilagin in CD3ODa.

Sudjaroen et al., 2012 Experimental

Glucose

1 95.1 95.1

2 69.4 71.3

3 71.6 71.8

4 62.5 61.7

5 76.2 77.1

6 65.0 65.2

Galloyl

1 120.7 120.4

2 111.0 111.0

3 146.4 146.3

4 140.4 140.9

5 146.4 146.6

6 111.0 111.0

Ring A

1 117.3 117.3

2 125.5 125.5

3 110.3 109.0

4 145.7 145.7

5 138.3 138.3

6 145.5 145.4

7 168.7 168.6

Ring B

1 116.8 116.4

2 125.6 125.7

3 108.4 108.3

4 146.0 146.3

5 137.8 137.7

6 145.4 145.4

7 170.2 170.1

a Obtained in ppm rel. TMS; 1H NMR 300 MHz.

J. Moreira et al. / Journal of Ethnopharmacology 146 (2013) 318–323 319

2. Material and methods

2.1. Plant material

Phyllanthus niruri L. (Euphorbiaceae) was collected in January2011 at Praia da Esplanada-Jaguaruna, Santa Catarina, Brazil. Theplant was authenticated by Professor Oscar Iza (UNIVALI) and avoucher specimen was deposited at the Barbosa Rodrigues Her-barium (HBR, Itajaı) under number VC Filho 075.

2.2. Extraction and isolation procedures

The whole plant (337 g, dry weight) was cut into small piecesand submitted to maceration with methanol at room temperaturefor 5 days, giving 30.98 g of the crude extract. 25 g of the extractwas solubilized in methanol/water (2:5 v/v) and extracted withdichloromethane (3 times, 2:1 v/v) and ethyl acetate (3 times,2:1 v/v), to give the dichloromethane (4.05 g), ethyl acetate(5.58 g) and methanol (10.74 g) fractions after evaporation. 1 gof the ethyl acetate fraction was submitted to chromatographyusing silica gel eluted with a dichloromethane/ethyl acetate/methanol gradient (40:55:5-0:0:100 v/v/v), giving six mainfractions. The third fraction (272.9 mg) was chromatographedusing isocratic flash chromatography (dichloromethane/ethyl acetate/methanol, 30:50:20 v/v/v), to give pure corilagin (88.4 mg). Thecompound with purity grade 495% was identified by 13C-NMRspectral data by comparison with those previously reported (Table 1).

2.3. Pharmacological procedures

2.3.1. Animals

Male Swiss mice weighting 25–30 g obtained from the AnimalFacility of the Universidade do Itajaı (UNIVALI, Itajaı, Brazil) wereused in this study. The animals were housed in plastic cages,under a 12 h light/dark cycle (lights on 7:00 a.m.) at constantroom temperature (23 1C72 1C) and humidity (60–80%) withwater and food ad libitum. The animals were acclimated to theexperimental room at least 1 h before each experiment. Theallocation of animals to the different groups was randomized,and the experiments were carried out in blind conditions. Eachgroup was constituted of 6–8 mice; each animal was used in oneexperiment only, and sacrificed immediately at the end of eachexperiment. All the experimental procedures were performed inaccordance with NIH publication no. 85–23—‘‘Principles ofLaboratory Animal Care’’ and with the approval of the UNIVALIEthics Committee, under protocol no. 599/2007.

2.3.2. Evaluation of antinociceptive activity in mice

2.3.2.1. Acetic acid-induced writhing test. Groups of mice (8/group)were treated with different doses of corilagin (1, 3, 6 and 10 mg/kg)by intraperitonial injection (i.p.) or by oral gavage (50 mg/kg).

Control animals received a similar volume of vehicle (10 mL/kg,0.9% NaCl solution). Acetic acid-induced writhing test (Collier et al.,1968) consisting of an i.p. injection of 10 mL/kg acetic acid (0.6% invehicle) 30 min after treatment of the animals, to cause abdominalconstrictions. Pairs of mice were placed in separate boxes and thenumber of abdominal constrictions was cumulatively counted overa period of 20 min. Antinociception was expressed as the reductionin the number of abdominal constrictions between the controlanimals and the mice pretreated with corilagin.

2.3.2.2. Formalin-induced paw licking test. The procedure wassimilar to that described previously (Hunskaar and Hole, 1987;Sakurada et al., 1993). Animals were treated with corilaginintraperitoneally at 3, 6, 10 mg/kg or vehicle (10 mL/kg, 0.9%NaCl solution), 30 min before formalin injection. The observationchamber was a glass cylinder of 20 cm in diameter, with a mirrorat a 451 angle to allow clear observation of the animal’s paws. The0.92% aqueous formalin solution was prepared as a 2.5% dilutionof analytical 37% formaldehyde solution in water (Hunskaar andHole, 1987). This solution was injected (20 mL) under the surfaceof the right hind paw. Two mice (control and treated) wereobserved simultaneously from 0 to 30 min following formalininjection. The amount of time spent licking the injected paw wasrecorded and expressed as the total licking time in the early phase(0–5 min) and late phase (15–30 min) after formalin injection,representing the tonic and inflammatory pain responses,respectively.

2.3.2.3. Capsaicin-induced nociception. The procedure used wassimilar to that described previously (Sakurada et al., 1993).Animals were placed individually in transparent glass cylinders.Following the adaptation period, 20 mL of capsaicin solution

Table 2Effects of different doses of corilagin against acetic acid-induced writhing in mice.

Compound dose (mg/kg i.p.) Inhibition (%) ID50

1 22.2 (74.85)n 4.10 (1.96–8.57) mg/kg or

6.46 (3.09–13.51) mmol/kg3 49.0 (71.59)nn

6 53.5 (73.35)nn

10 57.4 (72.46)nn

Each group represents the mean7SEM of 6–8 experimental values.n po0.05.nn po0.01 compared to the respective control values.

J. Moreira et al. / Journal of Ethnopharmacology 146 (2013) 318–323320

(1.6 mg/paw) was injected under the skin of the plantar surface ofthe right hind paw, using a micro-syringe. The animals wereobserved individually for 5 min following capsaicin injection. Theamount of time spent licking the injected paw was timed with achronometer and was considered as indicative of nociception. Theanimals were treated intraperitoneally with corilagin at 3 mg/kgor vehicle (10 mL/kg, 0.9% NaCl solution) 30 min beforeadministration of capsaicin.

2.3.2.4. Glutamate-induced nociception. Similarly to the proceduredescribed by Beirith et al. (2002), in this test animals were treatedwith corilagin i.p. at 3 mg/kg or vehicle (10 mL/kg, 0.9% NaClsolution) 30 min before glutamate injection. A volume of 20 mLglutamate solution (30 mmol/paw), made up in phosphatebuffered saline (PBS), was injected intraplantarly under thesurface of the right hind paw as described previously. Afterinjection with glutamate, the animals were individually placedinto glass cylinders of 20 cm in diameter and observed for 0 to15 min. The time spent licking and biting the injected paw wastimed with a chronometer and considered as indicative of pain.

2.3.2.5. Hot-plate test. The hot-plate test was used to estimate thelatency of responses according to the method described by Eddyand Leimback (1953) with minor modifications. The temperatureof the hot-plate was maintained at 5571 1C. The animals wereplaced on glass funnels on a heated surface, and the time betweenplacing the animals and the beginning of licking paws or jumpingwas recorded as the response latency index. Reaction time wasrecorded before and 30 min after i.p. administration of corilagin(3 mg/kg i.p.) or the same volume of vehicle (saline 10 mL/kg).A cut-off time of 20 s was chosen to indicate complete analgesiaand avoid tissue injury.

2.3.3. Measurement of motor performance

2.3.3.1. Rota-rod test. The interference of corilagin on motorcoordination was also evaluated (Duhnam and Miya, 1957). Thistest was performed using a horizontal rota-rod device (LeticaScientific Instrument, Barcelona, Spain) set to rotate at a constantspeed of 15 rpm. The animals were trained and then selected 24 hbefore the test by eliminating those mice that did not remain onthe bar for two consecutive periods of 60 s. The animals weretreated with compound (3 mg/kg, i.p.) or with the same volume of0.9% NaCl solution (10 mL/kg, i.p.) 30 min before being tested. Theresults are expressed as the time (s) the animals remained on therota-rod. The cut-off time used was 60 s.

2.3.3.2. Open field test. To exclude possible nonspecific effects ofcorilagin on locomotor activity, mice were treated with compound(3 mg/kg, i.p.) and after 30 min, the locomotor activity was assessedin the open-field test, as described previously (Bortolanza et al.,2002). The number of squares crossed with all paws (‘‘crossings’’) ina 6 min session was counted. The control mice received vehicle(10 mL/kg, i.p. 0.9% NaCl).

2.4. Statistical analysis

The results are presented as mean7SEM, except the meanID50 values (i.e. the dose of compound reducing the algesicresponses by 50% compared with the control value) which arereported as geometric means accompanied by their respective95% confidence limits. The statistical significance between groupswas analyzed by one-way ANOVA followed by Dunnett’s post-test, unless otherwise stated. P-values of less than 0.05 were

considered as indicative of significance. ID50 values were deter-mined by graphical interpolation from individual experiments.

2.5. Drugs

The following drugs were used: capsaicin and glutamate(Sigma Chemical Company, St. Louis, U.S.A); formalin, acetic acid(Vetec, Rio de Janeiro, Brazil). The compounds studied, as well asthe reference drugs, were dissolved in 0.9% of NaCl solution, withthe exception of capsaicin, which was dissolved in ethanol, plus0.9% of NaCl solution. The final concentration of ethanol did notexceed 5% and did not cause any effect ‘‘per se’’.

3. Results

3.1. Acetic acid-induced writhing test

The administration of corilagin 1, 3, 6 and 10 mg/kg i.p.reduced the number of writhing episodes induced by acetic acidby 22.2, 49.0, 53.5 and 57.4%, respectively, compared to thecontrol group (Table 2). ID50 calculated value (and its 95%confidence limits) was 6.46 (3.09–13.51) mmol/kg or 4.10 (1.96–8.57) mg/kg As oral administration of 50 mg/kg of corilagin didnot reduce acetic acid writhing responses, intraperitoneal admin-istration was preferred (Data not shown).

3.2. Formalin-induced paw licking test

In the formalin test, intraperitoneal pre-administration(30 min) of corilagin in different doses (3, 6 and 10 mg/kg)significantly reduced the formalin-induced licking in the earlyphase (po0.01), in a dose-dependent way, but not in the latephase (Fig. 2). The calculated ID50 (and its 95% confidence limits)was 18.38 (15.15–22.59) mmol/kg or 11.66 mg/kg (9.61–14.33).The 3 mg/kg corilagin was the lowest dose used in this studycapable of causing a marked inhibition in both, acetic acid andformalin tests. Therefore, this dose was chosen to be used in thesubsequent tests.

3.3. Capsaicin-induced pain

The effect of corilagin against capsaicin-induced nociception inmice is shown in Fig. 3A. Significant reduction of 32.6% wasobserved in the time spent on licking the paw in mice receivingcorilagin at the dose of 3 mg/kg compared to the control group(po0.01).

3.4. Glutamate-induced nociception

The corilagin dose of 3 mg/kg caused a significant inhibi-tion, 66.2% (po0.01), in the licking and biting behavior in

Fig. 2. Effects of corilagin administered intraperitoneally against formalin induced licking in mice (Panel A: early phase; Panel B: late phase). Each column represents the

mean7SEM (n¼6–8/group). Asterisks denote the significance levels, when compared to the control group, *po0.05; **po0.01. ANOVA followed by Dunnett’s test.

Fig. 3. Panel A: Effect of the intraperitoneal administration of corilagin (3 mg/kg) against capsaicin-induced nociception in mice. Panel B: Effect of the intraperitoneal

administration of corilagin (3 mg/kg) against glutamate-induced nociception in mice. Panel C: Effect of the intraperitoneal administration of corilagin (3 mg/kg) on the hot-

plate test in mice. Each column represents the mean7SEM (n¼6–8/group). Asterisks denote the significance levels, when compared to the control group, *po0.05;**po0.01. ANOVA followed by Dunnett’s test.

Fig. 4. Panel A: Effects of corilagin administered intraperitoneally on the rota-rod in mice. Each column represents the mean7SEM (n¼ 6–8/group). Panel B: Effects of

corilagin administered intraperitoneally on the open field test. Each column represents the mean7SEM (n¼ 6–8/group). Asterisks denote the significance levels, when

compared to the control group, *po0.05, **po0.01. ANOVA followed by Dunnett’s test.

J. Moreira et al. / Journal of Ethnopharmacology 146 (2013) 318–323 321

glutamate-induced nociception in mice, when compared to thecontrol group (Fig. 3B).

3.5. Hot-plate test

The i.p. administration of 3 mg/kg of corilagin did not changethe latency time to the nociceptive response of mice in the hotplate test (Fig. 3C).

3.6. Rota-rod test

As shown in Fig. 4A, corilagin (3 mg/kg i.p.) did not causesignificant alterations in the motor performance of mice in therota-rod test.

3.7. Open field test

Mice treated with corilagin (3 mg/kg i.p.) did not demonstratea statistical reduction in the number of crossings and rearingswhen compared to control group (Fig. 4B).

4. Discussion

Considering that corilagin is one of the major constituents ofPhyllanthus niruri and has a wide spectra of biological activities(Zhao et al., 2008; Chen and Chen, 2011), including anti-inflammatory activity, we investigated, in this work, the anti-hyperalgesic properties of this tannin using animals models ofpain behavior.

J. Moreira et al. / Journal of Ethnopharmacology 146 (2013) 318–323322

The acetic acid-induced writhing test is a classic visceral painmodel commonly used for assessment of potential antinocicep-tive and anti-inflamatory agents (Collier et al., 1968). In this test,pain is caused by acetic acid directly through the activation ofnon-selective cation channels present at primary afferent path-ways (Julius and Basbaum, 2001) and indirectly via release ofendogenous mediators, including bradykinin, substance P, pros-taglandins, histamine and others, which are able to increasevascular permeability, and to stimulate both peripheral nocicep-tive neurons and nerve terminal of nociceptive fibers (Derardtet al., 1980; Martinez et al., 1999; Ikeda et al., 2001).

Our results show that corilagin significantly reduced aceticacid writhing responses in a dose-dependent manner, which maysuggest that this tannin attenuates the release of inflammatoryendogenous mediators or blocks inflammation-promoting recep-tors, resulting in peripheral anti-hyperalgesic activity. However,even if acetic acid is a sensitive model for screening analgesicsubstances, it constitutes a non-specific model (Takahashi andPaz, 1987) and thus other tests such as formalin, capsaicin andglutamate were conducted to better characterize the anti-hyperalgesic pharmacology of corilagin. Comparison with pre-vious results (Santos et al., 1995a, 1995b) indicated that corilaginwas more potent than the hydroalcoholic extract obtained fromthis same plant.

The oral administration of corilagin was not able to inhibit thenociception induced by acetic acid. This result may be due to therapid metabolization of corilagin by intestinal microflora. It wasdemonstrated that the anaerobic incubation of the tannin with ratfecal suspension led to hydrolysis to several different metabolites,like gallic acid, ellagic acid and other derivatives. This hydrolysisseems to not occur by i.p. administration (Ito, 2011).

Two distinct phases constitute the formalin test. The first,called the neurogenic phase, starts immediately after formalininjection and seems to be elicited by direct activation of C-fibers(McNamara et al., 2007). The second (or inflammatory) phase is acombination of a peripheral inflammatory reaction responseinduced by release of nociceptive mediators, and changes incentral processing of pain (Hunskaar and Hole, 1987; Shibataet al., 1989; Tjølsen et al., 1992). Corilagin produced significantdose-dependent anti-hyperalgesic properties only in the neuro-genic phase of the formalin test. These findings strongly suggestthat corilagin could induce changes both in the direct activationof nociceptors and in the neurogenic pain response induced bythe release of mediators such as bradykinin, 5-hydroxytrypta-mine, histamine and adenosine triphosphate (Tjølsen et al., 1992;Sawynok and Liu, 2003). The lack of significant activity on thesecond phase of formalin test could be due to the hidrophilicity orhigh polar surface area of corilagin, which could selectively limitits passage to the brain (Kelder et al., 1999; Pardridge, 2007).

Nociception evoked by capsaicin occurs by activation of aligand-gated cation channel TRPV1 (or VR1 channel) (Caterinaet al., 1997). As a consequence, the release of several chemicalmediators, such as substance P, excitatory amino acids (asparticand glutamic acids), neurokinin A, calcitonin gene-related pep-tide, nitric oxide (NO) and pro-inflammatory mediators alsocontribute to increase nociception (Sakurada et al., 1993; Teohet al., 1996; Mohamad et al., 2010). Our results show thatcorilagin significantly reduced capsaicin-induced nociception,suggesting that the tannin may be involved in the antagonismof the TRPV1 receptor.

Another finding of our study is that corilagin also inhibited thenociceptive pain response induced by intraplantar injection ofglutamate into mouse hind paw. Glutamate can act in peripheral,spinal and supra-spinal areas that are involved in the processingof nociception. The glutamate peripheral induced-pain responseappears to be mediated through the activation of ionotropic

receptors by N-methyl-D-aspartate (NMDA), a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (non-NMDA ligand),as well as the release of NO or other NO-derived substances. NOrelease contributes to enhancing the inflammatory reactionthrough the induction of the synthesis of pro-inflammatorymediators such as cytokines (Fundytus, 2001; Beirith et al.,2002; Jesse et al., 2009; Mohamad et al., 2010). Thus, the anti-hyperalgesic activity of corilagin in the glutamate test may be dueto inhibition of NO production or to the interaction of corilaginwith the glutamatergic system.

Concerning the hot plate test, administration of corilagin 3 mg/kgi.p. in mice did not exert any change in response latency time to thethermal nociceptive stimulus when compared to the control group.Considering that the supraspinal and spinal opioid receptors play akey role in the hot plate assay, our results suggest that thiscompound does not act on the central opioid receptors, nor does itproduce a release of endogenous opioid peptides (Eddy andLeimback, 1953). Importantly, corilagin at 3 mg/kg i.p. was devoidof significant effects on locomotor activity and motor coordinationin mice (i.e. open field and rotarod test, respectively), eliminating thepossibility of non-specific muscle relaxation and sedative effects incorilagin-induced antinociception. This observation strongly sug-gests that the antinociceptive activities of corilagin measured in thisstudy are pharmacologically specific.

Several studies have reported that NMDA and non-NMDA receptorantagonists, as well as NO inhibitors, were able to inhibit nociceptioninduced by acetic acid, formalin, and glutamate (Fundytus, 2001;Jesse et al., 2009; Mohamad et al., 2010). In addition, Zhao et al.(2008) showed that corilagin was able to suppress the release of pro-inflammatory cytokines in vitro and reduced the production of NOand other pro-inflammatory mediators. Our study demonstrates forthe first time that intraperitoneal administration of corilagin pro-duced marked and significant dose-dependent suppression of noci-ceptive responses in all chemical nociceptive test models used andimportantly, that no alteration in motor performance contributed tothe observed behaviors of the animals.

Exact mechanism underlying the anti-hyperalgesic effects ofcorilagin remains unclear, but our results suggest that its anti-hyperalgesic properties could be due in part to the inhibition ofNO production and release of pro-inflammatory mediators suchas cytokines as well as the potential interaction with the gluta-matergic system.

Several studies from our and other research groups haveevidenced the antinociceptive activity of Phyllanthus niruri andother species of the genus, sometimes attributing this effect toboth polar and non-polar compounds (Calixto et al., 1998).However, this is the first time that the antinociceptive potentialof corilagin is demonstrated.

Our findings presented herein are of interest because theysupport the idea that corilagin, a tannin isolated from Phyllanthus

niruri, may be used for the development of potentially novel andeffective peripheral analgesics devoted to the control of pain.

Acknowledgment

We are grateful to Conselho Nacional de DesenvolvimentoCientıfico e Tecnologico (CNPq) and Universidade do Vale do Itajaı(UNIVALI) for their financial support. The authors also wish to thankProfessor Oscar Iza for the assistance with plant authentication.

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