Antioxidant activity of nimesulide and its main metabolites

Plasma and Synovial Fluid Concentrations of Nimesulide and its Main Metabolite after a Single or Repeated Oral Administration in Patients with Knee Osteoarthritis

The aim of this study was to evaluate plasma and synovial fluid concentrations of the non-steroidal anti-inflammatory drug nimesulide and its major metabolite (hydroxynimesulide, M1), after a single 100 mg dose of nimesulide and a repeated (14 day) administration, 100 mg twice a day, in patients with osteoarthritis of the knee and joint effusion. Nimesulide was rapidly absorbed in plasma and distributed in synovial fluid. On day 1, effective concentrations were present 30 min after the first dose and on day 14, the synovial fluid concentration of nimesulide was significantly higher than that measured on day 1; no accumulation was observed in plasma. After 14 days of treatment, both the plasma and synovial fluid concentrations of M1 were significantly higher than those measured on day 1. These data may help to explain the rapid onset of the analgesic effect of nimesulide demonstrated in several clinical conditions, including painful osteoarthritis.

Development of Antioxidant COX-2 Inhibitors as Radioprotective Agents for Radiation Therapy-A Hypothesis-Driven Review

Radiation therapy (RT) evolved to be a primary treatment modality for cancer patients. Unfortunately, the cure or relief of symptoms is still accompanied by radiation-induced side effects with severe acute and late pathophysiological consequences. Inhibitors of cyclooxygenase-2 (COX-2) are potentially useful in this regard because radioprotection of normal tissue and/or radiosensitizing effects on tumor tissue have been described for several compounds of this structurally diverse class. This review aims to substantiate the hypothesis that antioxidant COX-2 inhibitors are promising radioprotectants because of intercepting radiation-induced oxidative stress and inflammation in normal tissue, especially the vascular system. For this, literature reporting on COX inhibitors exerting radioprotective and/or radiosensitizing action as well as on antioxidant COX inhibitors will be reviewed comprehensively with the aim to find cross-points of both and, by that, stimulate further research in the field of radioprotective agents.

Nimesulide may be more efficient than allopurinol in protecting pancreas from acute ischemia/reperfusion injury in an animal model

OBJECTIVE

To determine the influence of allopurinol and nimesulide in the protection of the pancreas from acute ischemia-reperfusion (I/R) injury.

MATERIALS AND METHODS

A total of 30 rabbits were divided into 3 groups, group A: acute I/R only; group B: allopurinol (30 mg/kg) was administered intravenously 10 minutes before ischemia; group C: nimesulide (50 mg/kg) was given intraperitoneally 20 minutes before ischemia. Neopterin and superoxide dismutase (SOD) levels were examined. Pancreatic biopsies were obtained for electron microscopy study.

RESULTS

The mean neopterin concentrations in group A are 3.56 ± 3.41, 7.74 ± 3.59, and 8.94 ± 2.86 ng/mL, respectively, in the stabilization, ischemia, and reperfusion phases; group B: 3.40 ± 3.03, 7.45 ± 8.89, and 10.64 ± 7.47 ng/mL; and group C: 3.41 ± 2.71, 5.67 ± 2.76, and 4.34 ± 2.87 ng/mL. The mean SOD concentrations in group A are 4.25 ± 1.79, 4.48 ± 1.60, and 5.57 ± 1.15 ng/mL; group B: 4.32 ± 0.81, 5.08 ± 1.10, and 4.45 ± 1.31 ng/mL; and group C: 4.10 ± 0.99, 5.23 ± 1.60, and 3.72 ± 1.30 ng/mL. Histopathology showed the least deterioration in group C.

CONCLUSION

Nimesulide is more efficient than allopurinol in protecting pancreas from acute I/R injury.

Analgesic and Anti-Inflammatory Activities ofTorenia concolorLindley var.formosanaYamazaki and Betulin in Mice

The present study was intended to examine the analgesic effect of the 70% methanol extract of Torenia concolor Lindley var. formosana Yamazaki (TCMeOH) and betulin using models of acetic acid-induced writhing response and formalin test. In addition, we investigated the anti-inflammatory effect of TCMeOHand betulin using model of λ-carrageenan-induced paw edema. We observed the activities of antioxidant enzymes (SOD, GPx and GR) in the liver and the levels of malondialdehyde (MDA) and nitric oxide (NO) in the edema paw. The results showed that TCMeOH(1.0 and 2.0 g/kg) and betulin (30 and 90 mg/kg), significantly inhibited the acetic acid-induced writhing response. TCMeOH(2.0 g/kg) and betulin (30 and 90 mg/kg) significantly inhibited formalin-induced licking time during both the early and late phases. TCMeOH(0.5, 1.0 and 2.0 g/kg) and betulin (30 and 90 mg/kg) also significantly decreased the paw edema at the 4th hour after λ-carrageenan injection. Furthermore, TCMeOHand betulin treatment also significantly increased the activities of SOD, GR and GPx in the liver while decreasing the level of MDA in the edema paw. Finally, betulin (30 and 90 mg/kg) also caused considerable reduction of NO level in the edema paw. Taken together, the present results indicated that TCMeOHand betulin possessed analgesic and anti-inflammatory effects. The anti-inflammatory mechanism of TCMeOHand betulin may be related to decreasing the levels of MDA and NO in the edema paw by increasing the activities of antioxidant enzymes in the liver.

Cyclo-oxygenase-2, endothelium and aortic reactivity during deoxycorticosterone acetate salt-induced hypertension

OBJECTIVE

To test the hypothesis that the enhanced vascular responsiveness to norepinephrine that occurs during deoxycorticosterone acetate (DOCA)-salt induced hypertension is causally related to increased expression of cyclo-oxygenase (COX)-2 and oxidative stress, which diminishes the vasomodulatory influence of endothelium-derived nitric oxide.

METHODS

Four groups of age-matched, male Sprague-Dawley rats were studied: Sham (normotensive); DOCA-salt (hypertensive); DOCA-salt treated with manganese(III) tetra(4-benzoic acid) porphyrin chloride [MnTBAP, an antioxidant; 15 mg/kg intraperitoneally (i.p.) for 21 days]; DOCA-salt treated with {N-[2-(cyclohexyloxy)-4-nitrophenyl]-methane sulfonamide} (NS-398, a COX-2 selective blocker; 5 mg/kg i.p. for 7 days). Contraction and relaxation were measured with FT03 force transducers coupled to a Grass polygraph in aortic rings bathed with physiologic salt solution (37 degrees C) and bubbled with a 5%CO2/95%O2 gas mixture. Aortic sensitivities (pD2 values) to norepinephrine and serum isoprostanes (8-iso-prostaglandin F2alpha, a marker of oxidative stress) were measured for each experimental paradigm.

RESULTS

NS-398 significantly reduced maximal contractions in response to norepinephrine in aortic rings from Sham (44 +/- 3%) and DOCA-salt (96 +/- 2%) group rats. Expression of COX-2 protein increased significantly in vessels from DOCA-salt rats compared with those from Sham group rats. Treatment of DOCA-salt rats with either MnTBAP or NS-398 alleviated hypertension, normalized aortic pD2 values for norepinephrine and restored serum 8-isoprostane concentrations towards those observed in Sham group rats.

CONCLUSIONS

COX-2 expression increases during DOCA-salt hypertension, and mediates production of factors that enhance rat aortic contractility in response to norepinephrine. Our data also suggest a role for increased oxidative stress, which is at least in part dependent on enhanced COX-2 expression, in the mechanism(s) of enhanced aortic contractility in response to norepinephrine during DOCA-salt hypertension.

Detection of nimesulide metabolites in rat plasma and hepatic subcellular fractions by HPLC-UV/DAD and LC-MS/MS studies

Nimesulide (4-nitro-2-phenoxymethanesulfonanilide) is an atypical NSAID lacking a carboxylic acid moiety. It has a good gastric tolerability due to selective inhibition of COX-2. The study objectives in the present work were to characterize the metabolism of nimesulide in rat plasma at certain time intervals. In vitro studies were also carried out to examine if nitroreduction takes place in vitro using rat hepatic subcellular fractions (microsomal and S9 fraction) besides aromatic hydroxylation. This communication describes detection and characterization of nimesulide metabolites isolated from plasma and hepatic subcellular post-incubates by the use of HPLC-UV/diode array and LC-MS/MS. Hydroxynimesulide was the major metabolite both in vivo and in vitro whereas nitroreduction was observed only in vitro with subcellular fractions under anaerobic conditions.

Indomethacin potentiates acetylcholine-induced vasodilation by increasing free radical production

We studied the effects of indomethacin on endothelium-dependent and -independent vascular relaxation in rat thoracic aortic rings and its role in superoxide anion (O(2)(-)) production. We measured isometric force changes in response to acetylcholine (Ach, 1 nM-0.1 mM), sodium nitroprusside (SNP, 0.1 nM-0.1 microM; a nitric oxide (NO) donor) and cromakalim (1 nM-0.1 mM; a K(ATP)-channel opener) in aorta rings contracted with norepinephrine (NE, 0.1 microM). Indomethacin (10 microM; 20 min) significantly increased Ach-induced vasodilation (EC(50) decreased from 8.99 microM to 16 nM). The free radical scavengers superoxide dismutase and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl completely reverted these effects. Indomethacin did not affect SNP- or cromakalim-induced vasodilation. Neither acetylsalicylic acid (ASA, 5-100 microM; 15 min) nor ketoprofen (1-100 microM; 15 min) affected Ach, SNP and cromakalim concentration-response curves. Incubation of the aorta with Ach (1 microM) rapidly and markedly increased intracellular NO fluorescence in the aorta endothelium. Indomethacin did not affect Ach-induced NO production. We measured intracellular O(2)(-) in the aorta endothelium with dihydroethidium (DHE) dye. Indomethacin significantly increased O(2)(-) fluorescence versus controls. Neither ASA nor ketoprofen affected O(2)(-) fluorescence. Nitrotyrosine staining was increased in indomethacin-treated aorta sections exposed to Ach, which indicates endogenous formation of peroxynitrite. It was low in aorta sections exposed to Ach alone or with ASA or ketoprofen. We cannot judge if indomethacin-induced endothelium-dependent vasodilation damages or protects the cardiovascular system. Here, we show that indomethacin acts on the cardiovascular system regardless of cyclooxygenase inhibition.

Effect of nimesulide on acetic acid- and leukotriene-induced inflammatory bowel disease in rats

Inflammatory bowel disease (IBD) is a relapsing inflammation of intestine, which is mediated by release of inflammatory mediators. Both cyclo-oxygenase product prostaglandin (PGE2) and lipo-oxygenase product leukotriene (LTB4), may contribute to the pathogenesis of the inflammatory response. Nimesulide, a preferential COX-2 inhibitor was evaluated for its efficacy against experimental colitis in two different models (acetic acid- and LTB4-induced IBD) in rats. Inflammatory response was induced by intrarectal single administration of acetic acid or LTB4. Nimesulide (9 and 18 mg/kg, p.o.) significantly prevented development of inflammatory changes, decreased myeloperoxidase (MPO) activity, and also restored the altered contractility response of the isolated colon segment to KCl. The results suggested the involvement of both cyclo-oxygenase (COX) and lipo-oxygenase-mediated proinflammatory agents in colonic inflammatory process associated with IBD. Further, this study suggests that such therapeutic interventions may be of value in the treatment of IBD.

In vivo effects of meloxicam, celecoxib, and ibuprofen on free radical metabolism in human erythrocytes

One of the major groups of chemical mediators involved in the inflammatory response is the prostaglandins, which are synthesized from arachidonic acid by the enzyme cyclooxygenase. The aim of this study is to compare the in vivo effects of celecoxib, meloxicam, and ibuprofen on the activities of catalase (CAT), glutathione peroxidase (GSHPx), superoxide dismutase (SOD) as well as malondialdehyde (MDA), and antioxidant potential levels (AOP) in human erythrocytes. Patients diagnosed as osteoarthritis were included in the study. Patients were treated with Celecoxib (200 mg/d) (n = 12), Meloxicam (15 mg/d) (n = 12), and Ibuprufen (1200 mg/d) (n = 9) for 21 days. SOD, CAT, GSHPx activities, MDA, and AOP levels were investigated in human erythrocyte haemolysates. SOD activity and AOP levels were significantly decreased in all NSAID groups when we compared the values before and after 21 days of celecoxib, meloxicam, ibuprofen treatment. There were no significant difference in CAT, GSHPx activities, and MDA levels before and after treatment in each group. Decreased SOD activities are thought to be related with the increased superoxide anion. Decreased AOP levels may indicate impairment in the total antioxidant defence system. These NSAIDs have similar effects on free radical metabolism on human erythrocytes; despite some difference in action mechanisms.

Effects of nimesulide on kainate-induced in vitro oxidative damage in rat brain homogenates

BACKGROUND

The cyclooxygenase-2 inhibitor nimesulide is able to reduce kainate-induced oxidative stress in vivo. Here we investigate if this effect is mediated by the direct antioxidant properties of nimesulide using a well-characterized in vitro model of kainate toxicity.

RESULTS

Exposure of rat brain homogenates to kainate (12 mM) caused a significant (p < 0.01) increase in the concentrations of malondialdehyde and 4-hydroxy-alkenals and a significant (p < 0.01) decrease in sulfhydryl levels. High concentrations of nimesulide (0.6-1.6 mM) reduced the extent of lipid peroxidation and the decline in both total and non-protein sulfhydryl levels induced by kainate in a concentration-dependent manner.

CONCLUSIONS

Our results suggest that the neuroprotective effects of nimesulide against kainate-induced oxidative stress in vivo are not mediated through its direct free radical scavenging ability because the concentrations at which nimesulide is able to reduce in vitro kainate excitotoxicity are excessively higher than those attained in plasma after therapeutic doses.

Neuroprotective efficacy of nimesulide against hippocampal neuronal damage following transient forebrain ischemia

Cyclooxygenase-2 is involved in the inflammatory component of the ischemic cascade, playing an important role in the delayed progression of the brain damage. The present study evaluated the pharmacological effects of the selective cyclooxygenase-2 inhibitor nimesulide on delayed neuronal death of hippocampal CA1 neurons following transient global cerebral ischemia in gerbils. Administration of therapeutically relevant doses of nimesulide (3, 6 and 12 mg/kg; i.p.) 30 min before ischemia and at 6, 12, 24, 48 and 72 h after ischemia significantly (P<0.01) reduced hippocampal neuronal damage. Treatment with a single dose of nimesulide given 30 min before ischemia also resulted in a significant increase in the number of healthy neurons in the hippocampal CA1 sector 7 days after ischemia. Of interest is the finding that nimesulide rescued CA1 pyramidal neurons from ischemic death even when treatment was delayed until 24 h after ischemia (34+/-9% protection). Neuroprotective effect of nimesulide is still evident 30 days after the ischemic episode, providing the first experimental evidence that cyclooxygenase-2 inhibitors confer a long-lasting neuroprotection. Oral administration of nimesulide was also able to significantly reduce brain damage, suggesting that protective effects are independent of the route of administration. The present study confirms the ability of cyclooxygenase-2 inhibitors to reduce brain damage induced by cerebral ischemia and indicates that nimesulide can provide protection when administered for up to 24 h post-ischemia.

A natural protective mechanism against hyperglycaemia in vascular endothelial and smooth-muscle cells: role of glucose and 12-hydroxyeicosatetraenoic acid

Bovine aortic endothelial and smooth-muscle cells down-regulate the rate of glucose transport in the face of hyperglycaemia, thus providing protection against deleterious effects of increased intracellular glucose levels. When exposed to high glucose concentrations these cells reduced the mRNA and protein content of their typical glucose transporter, GLUT-1, as well as its plasma-membrane abundance. Inhibition of the lipoxygenase (LO) pathway, and particularly 12-LO, reversed this glucose-induced down-regulatory process and restored the rate of hexose transport to the level seen in vascular cells exposed to normal glucose levels. This reversal was accompanied by increased levels of GLUT-1 mRNA and protein, as well as of its plasma-membrane content. Exposure of the vascular cells to elevated glucose concentrations increased by 2-3-fold the levels of cell-associated and secreted 12-hydroxyeicosatetraenoic acid (12-HETE), the product of 12-LO. Inhibition of 15- and 5-LO, cyclo-oxygenases 1 and 2, and eicosanoid-producing cytochrome P450 did not modify the hexose-transport system in vascular cells. These results suggest a role for HETEs in the autoregulation of hexose transport in vascular cells. 8-Iso prostaglandin F(2alpha), a non-enzymic oxidation product of arachidonic acid, had no effect on the hexose-transport system in vascular cells exposed to hyperglycaemic conditions. Taken together, these findings show that hyperglycaemia increases the production rate of 12-HETE, which in turn mediates the down-regulation of GLUT-1 expression and the glucose-transport system in vascular endothelial and smooth-muscle cells.

Effect of nimesulide and indomethacin on contractility and the Ca2+ channel current in myometrial smooth muscle from pregnant women

The non-steroidal anti-inflammatory drug (NSAID) indomethacin inhibits both constitutive and inducible forms of cyclo-oxygenase (COX-1 and COX-2, respectively), while nimesulide is a selective COX-2 inhibitor. Uterine COX-2 is upregulated before and during term and pre-term labour, and prostaglandins play a crucial role in parturition. We therefore evaluated the effects of these drugs on myometrial contractility and the voltage-gated Ca2+ channel current in tissue strips and isolated human myometrial smooth muscle cells (HMSMC) from myometrial biopsies taken with informed consent from women undergoing caesarean section at term (not in labour). Nimesulide and indomethacin caused almost complete inhibition of spontaneous myometrial contractions at concentrations of 100 and 300 microM, respectively. The Ca2+ channel current was inhibited in a concentration-dependent manner by both drugs, with a 40% reduction of the current at 100 microM nimesulide and 300 microM indomethacin. Nimesulide also accelerated the decay of the Ca2+ channel current. The inhibition of the Ca2+ channel current by 100 microM nimesulide and 300 microM indomethacin was unaffected by the presence of either PGF2alpha or PGE2 (30 microM), and was of similar magnitude whether 10 mM Ba2+ or 1.5 mM Ca2+ was used as the charge carrier. The concentrations of indomethacin and nimesulide required to suppress spontaneous contractility in human pregnant myometrium were much higher than those necessary to inhibit prostaglandin production. The results suggest that both nimesulide and indomethacin inhibit myometrial contractility via mechanisms independent of cyclo-oxygenase inhibition. Blockade of the Ca2+ current may contribute to this effect.

Mass spectrometric characterization and HPLC determination of the main urinary metabolites of nimesulide in man

A study was undertaken for the characterization and quantitative determination of the main urinary metabolites of the non-steroidal anti-inflammatory drug (NSAID) nimesulide (4-nitro-2-phenoxy-methanesulfonanilide) in man following single oral administration (200 mg). Urines were collected from six healthy volunteers at 12, 24, 48, 72 and 96 h post-administration and submitted to liquid liquid extraction before (free metabolites) and after enzymatic hydrolysis (conjugated metabolites). The structure of the metabolites, isolated by TLC separation, was elucidated by mass spectrometry (electron impact ionization) and confirmed by synthesis. Five metabolites were identified: they arise from hydroxylation to the phenoxy nucleus (M1 = hydroxynimesulide); reduction of the nitro group to an amino derivative (M2); concomitant hydroxylation and reduction (M3); N-acetylation of the M2 (M4) and of the M3 (M5) metabolites. Quantitation was by reverse phase high performance liquid chromatography (Supelcosil LC-18 DB column; mobile phase: sodium phosphate buffer (pH 3.0, 50 mM)-acetonitrile (gradient elution); flow rate: 1 ml min(-1); UV detection, 230 nm), procedure which allows in a single chromatographic run the simultaneous determination of the unchanged drug and of its metabolites. The urinary excretion of the drug and metabolites (free + conjugated) in the overall 96 h-interval accounts for approximately 40% of the administered dose: 17.55 +/- 3.6% M1; 0.72 +/- 0.43% M2; 2.45 +/- 1.22% M3; 19.07 +/- 4.3% M5. The bulk of the metabolites was in conjugated form. Percentages excretion of the unchanged drug and of M4 metabolite were below 0.5%. The described method is suited to specifically and quantitatively measure nimesulide and metabolites in human urine with acceptable precision and accuracy.

Clinical pharmacokinetics of nimesulide

Nimesulide is a selective COX-2 inhibitor used in a variety of inflammatory, pain and fever states. After healthy volunteers received oral nimesulide 100 mg in tablet, granule or suspension form the drug was rapidly and extensively absorbed. Mean peak concentrations (Cmax) of 2.86 to 6.50 mg/L were achieved within 1.22 to 2.75 hours of administration. The presence of food did not reduce either the rate or extent of nimesulide absorption. When nimesulide was administered in the suppository form, the Cmax was lower and occurred later than after oral administration; the bioavailability of nimesulide via suppository ranged from 54 to 64%, relative to that of orally administered formulations. Nimesulide is rapidly distributed and has an apparent volume of distribution ranging between 0.18 and 0.39 L/kg. It is extensively bound to albumin; the unbound fraction in plasma was 1%. The unbound fraction increased to 2 and 4% in patients with renal or hepatic insufficiency. With oral administration, the concentrations of nimesulide declined monoexponentially following Cmax. The estimated mean terminal elimination half-life varied from 1.80 to 4.73 hours. Excretion of the unchanged drug in urine and faeces is negligible. Nimesulide is largely eliminated via metabolic transformation and the principal metabolite is the 4'-hydroxy derivative (M1). Minor metabolites have been detected in urine and faeces, mainly in a conjugated form. Pharmacological tests in vivo have shown that the metabolites are endowed with anti-inflammatory and analgesic properties, although their activity is lower than that of nimesulide. Excretion in the urine and faeces accounted for 50.5 to 62.5% and 17.9 to 36.2% of an orally administered dose, respectively. The total plasma clearance of nimesulide, was 31.02 to 106.16 ml/h/kg, reflecting almost exclusive metabolic clearance. The drug has a low extraction ratio, close to 0.1. With twice daily oral or rectal administration of nimesulide, steady-state was achieved within 24 to 48 hours (2 to 4 administrations); only modest accumulation of nimesulide and M1 occurred. Gender has only a limited influence on the pharmacokinetic profiles of nimesulide and M1. The pharmacokinetic profiles of nimesulide and M1 in children and the elderly did not differ from that of healthy young individuals. Hepatic insufficiency affected the pharmacokinetics of nimesulide and M1 to a significant extent: the rate of elimination of nimesulide and M1 was remarkably reduced in comparison to the rate of elimination in healthy individuals. Therefore, a dose reduction (4 to 5 times) is required in patients with hepatic impairment. The pharmacokinetic profile of nimesulide and M1 was not altered in patients with moderate renal failure and no dose adjustment in patients with creatinine clearances higher than 1.8 L/h is envisaged. Pharmacokinetic interactions between nimesulide and other drugs given in combination [i.e. glibenclamide, cimetidine, antacids, furosemide (frusemide), theophylline, warfarin and digoxin] were absent, or of no apparent clinical relevance.

An analysis from clinico-epidemiological data of the principal adverse events from the COX-2 selective NSAID, nimesulide, with particular reference to hepatic injury

The safety of the cyclo-oxygenase-2 (COX-2) selective NSAID, nimesulide, has been evaluated from information (a) in clinical trials in osteoarthritis that have been performed in Europe as well as in earlier pilot studies that were performed in patients with rheumatoid arthritis in the USA, and (b) in post-marketing studies (PMS) that have been performed by the manufacturer since the introduction of the drug in Europe and some South American countries. Upon analysis there have been clear indications of elevation of liver enzymes being related to the drug in 3/753 patients who were investigated in clinical trials in osteoarthritis. The results of the analysis of adverse drug reactions (ADRs) in patients with osteoarthritis (which is the principal indication for the drug) in PMS showed that the greatest number of these were in the skin and appendages, digestive system and organs wherein metabolic effects were manifest. There was a relatively low number of reports of gastrointestinal ulceration and haemorrhage, and these observations are in agreement with published experimental studies in humans and laboratory animals. Recent reports of ADRs in the liver in 25 patients were analysed in detail. In many of the cases there was evidence of confounding disease (e.g. cancer, prior liver damage) or prior or concurrent intake of known hepatotoxic NSAIDs (diclofenac, aspirin). Often elevations of liver enzymes above the laboratory norms are the only indication of liver injury and this in many cases is variable. The major cases of elevated liver enzymes and other liver changes have been in elderly patients.This first extensive analysis of ADRs from a COX-2 selective NSAID, nimesulide, indicates that there is a relatively low incidence of ADRs especially in the gastrointestinal tract, while those in the liver are within or below the general incidence with other NSAIDs.

Anti-inflammatory action of Pluchea sagittalis: involvement of an antioxidant mechanism

Pluchea sagittalis, (Lam.) Cabr., a popular medicinal herb grown in South America, was studied for anti-inflammatory and antioxidant activities. The anti-edema action of P. sagittalis aqueous extract was assayed in different models of inflammation: 1) the mouse ear edema test induced by arachidonic acid and croton oil; 2) the rat hind-paw edema test produced by several inflammatory inductors: carrageenan, dextran, zymosan, platelet-activating factor (PAF) and arachidonic acid; 3) a subacute model based on the rat carrageenan air-pouch granuloma test. Blood leukocyte free radical production was measured by flow cytometry with 2',7'-dichlorofluorescin diacetate (DCFH-DA) in vivo, in rats with induced air-pouch granuloma, and in a model in vitro. stimulating leukocytes with hydrogen peroxide. The aqueous extract of P. sagittalis showed a marked anti-inflammatory effect in both ear edema tests, dextran and carrageenan hind-paw edemas and carrageenan air-pouch model. It also had a potent antioxidant activity in blood leukocytes, both in vivo and in vitro. Our results correlate the reduction of free radical production with the anti-inflammatory effect of this plant.