Male rat copulatory behavior is dependent on Testosterone (T) and its metabolites, estradiol (E2) and dihydrotestosterone (DHT). The estrogen receptor (ER) isoforms, ERα and ERβ, exist in the medial Amygdala (MEA) and either receptor might mediate mating behavior. Therefore, the effects of selective estrogenic MEA implants: propyl pyrazole triol (PPT, ERα agonist), diarylpropionitrile (DPN, ERβ agonist), and 1-methyl-4-phenyl pyridinium (MPP, ERα antagonist) were compared to E2 in maintaining sexual behavior. Four groups of male rats were castrated and administered DHT s.c. and bilateral MEA implants containing either cholesterol, E2, PPT or DPN. An additional group of gonadally intact male rats received bilateral MPP-MEA implants. The post-surgical trials showed a significant decrease in the mating behavior of groups that received cholesterol, PPT, or DPN-MEA implants. However, sexual behavior was maintained in male rats that received the E2 or MPP-MEA implants. These results suggest a differential response of the MEA to E2.

Many heterocyclic compounds containing nitrogen, oxygen and sulfur show wide range of physiological activities and their synthesis has always been attracted the interest of chemists. The aim of this research is to develop new synthetic methodologies leading to the synthesis of new derivatives of isocoumarines, indoles, isoquinolines, benzodiazepinones and quinazolines, which have been found to show important biological activities. Starting from homophthalic acid and bishomophthalic acid the corresponding acyl azides were proposed to be synthesized, which then would be used for the synthesis of various heterocycles. The proposed diazide from homophthalic was not formed due to the tendency of the ortho-positioned acid to undergo cyclization. Instead, new unusual benzochromen and isocoumarin derivatives have been synthesized in a single step, for which reasonable mechanisms have been proposed. The half ester produced from homophthalic acid was an important key compound for the synthesis of new highly substituted indole derivatives, which are expected to be biologically active. The diisocyanate derived from was synthesized directly from ortho-bromo xylene was treated with alcohols and hydrazine to produce seven membered rings. Instead of the intramolecular cyclization reaction, they underwent polymerization to form new polymers. Furthermore, new synthetic method for the synthesis of pyrazoles has been developed.

Pyrazoles have been studied for over a century as an important class of heterocyclic compounds and continue to attract considerable interest due to the broad range of biological activities they possess. The electrophilic cyclization of the acetylenic hydrazones initiated by molecular iodine could provide new ways of synthesizing biologically active 4-iodopyrazole derivatives, which are important precursors for the synthesis of highly substituted pyrazole derivatives. For this reason, we investigated the synthesis of 4-iodopyrazole derivatives, such as 1-aryl- 5-alkyl/aryl-4-iodopyrazoles, starting from phenylhydrazine and ,-acetylenic aldehyde derivatives. Initially, ,-acetylenic aldehydes were synthesized by formylation reaction of corresponding alkynes with DMF. Then, hydrazone derivatives of these aldehydes were prepared by heating them with phenylhydrazine in a neat manner at 55 &deg / C for 5 h. Finally, acetylenic phenyl hydrazone derivatives were subjected to electrophilic cyclization by treating with excess molecular iodine at 80 &deg / C for 3 h. Although electrophilic cyclization is commonly used in organic chemistry, it has not been employed for the cyclization of acetylenic phenyl hydrazones to pyrazole derivatives. Under optimized conditions, these reactions afforded 1-aryl-5-alkyl/aryl-4-iodopyrazole derivatives in moderate to good yields as the single or the major product of the reactions. In some cases, 1-aryl-5-alkyl/arylpyrazole derivatives resulted from these reactions as minor products. In conclusion, 4-iodopyrazole derivatives were synthesized for the first time directly from acyclic starting materials, ,-acetylenic phenylhydrazones and iodine, via electrophilic cyclization.

Pyrazoles constitute one of the most important classes of heterocyclic compounds due to their interesting chemical and biochemical features. Researchers have studied many pyrazole containing structures for almost over a century in order to investigate the various biological activities possessed by these molecules. A new and important trend in these studies is to produce ferrocenyl substituted pyrazoles since ferrocene attracts considerable interest in the research field of organometallic and bioorganometallic chemistry because of its valuable chemical characteristics like high stability, low toxicity and enhanced redox properties. Moreover, the results of the studies focusing on ferrocenyl compounds have been quite promising. Therefore, the scope of this project involves the combination of the essential structural features of pyrazoles with a ferrocene moiety, which could provide new derivatives with enhanced biological activities. In the course of the project the synthesis of new pyrazole derivatives was performed through Sonogashira and Suzuki-Miyaura cross-coupling reactions of 5-ferrocenyl-4-iodo-1-phenyl-1H-pyrazole with terminal alkynes and boronic acids respectively in the presence of a catalytic amount of PdCl2(PPh3)2. Although Sonogashira and Suzuki-Miyaura coupling reactions are well known in literature, they were not studied in much detail with multi-substituted pyrazoles. This also revealed the requirement of the reinvestigation of the reactions and improvement of the yields of pyrazoles by optimizing the reaction conditions.

Synthesis of five-membered heteroaromatic compounds such as pyrazoles, isoxazoles and 1,2,4-oxadiazoles are important for pharmaceutical industry and material science due to their applications. Although there are many methods to prepare such compounds, new variants continue to appear since they exhibit a wide range of biological and medicinal activities. In this thesis, new methods were developed for the synthesis of 4-iodopyrazoles, pyrazoles, isoxazoles, 1,2,4-oxadiazoles and/or 1,2,4-oxadiazepines. In the first part of the study, electrophilic cyclization of &alpha / ,&beta / -alkynic hydrazones by molecular iodine and copper iodide were investigated as new ways for the synthesis of 4-iodopyrazoles and pyrazoles, respectively. Initially, &alpha / ,&beta / -alkynic hydrazones were prepared by the reactions of propargyl aldehydes and ketones with hydrazines. Then &alpha / ,&beta / -alkynic hydrazones were treated with molecular iodine in the presence of NaHCO3, which afforded 4-iodopyrazoles in good to excellent yields. Subsequently, the same reactions were carried out with CuI in the presence of NEt3, which furnished corresponding pyrazoles in good yields. Moreover, ferrocenyl-substituted 4-iodopyrazoles and pyrazole derivatives were synthesized from corresponding

In this study, the synthesis of 5-ferrocenyl/aryl-4-(phenylselenyl)-1H-pyrazole derivatives was investigated since the integration of ferrocenyl and selenium moieties into pyrazole derivatives may increase their current biological activities. Initially, the starting propargyl aldehydes were synthesized from corresponding acetylenes. Subsequently, propargyl aldehydes were reacted with hydrazines to yield corresponding hydrazones. Then the in situ synthesized hydrazones were subjected to electrophilic cyclization with phenylselenyl chloride, which afforded 5-ferrocenyl/aryl-4-(phenylselenyl)-1H-pyrazoles in one-pot manner. Subsequently, reaction conditions were optimized in terms of electrophile, base, temperature and solvent. Best results were obtained with phenylselenyl chloride and NaHCO3 at room temperature in DCM for ferrocenyl substituted pyrazoles and DCE for aryl substituted pyrazoles. In summary, by employing the electrophilic cyclizations of in situ synthesized acetylenic hydrazones, a variety of 5-ferrocenyl/aryl-4-(phenylselenyl)-1H-pyrazole derivatives were synthesized in one-pot way in moderate to good yields.

ABSTRACT Evidence from knockout studies in male mice and from experiments in male rats,in which expression of the estrogen receptor alpha (ERα) gene was inhibited in the medial preoptic area (MPO), suggests that ERα is important in the control of male rat mating behavior. Therefore, in this experiment, we tested the hypothesis that activation of ERα in the MPO is sufficient to maintain mating behavior in castrated male rats receiving subcutaneously (s.c.) dihydrotestosterone (DHT), a non-aromatizable androgen. Accordingly, castrated rats treated with DHT s.c. received MPO implants of either: (i) propyl-pyrazole-triol (PPT) (Stauffer, et al 2000; Katzenellenbogen, et al 2000), a selective ERα agonist, (ii) E2 (positive controls) or (iii) cholesterol (negative controls)and sexual behavior was monitored. PPT was as effective as E2 at maintaining mating behavior suggesting that, in the MPO, ERα is sufficient to mediate responses to E2 that underlie male rat mating behavior.

Abstract Peroxisome proliferator-activated receptors (PPARs) are transcription factors that belong to the family of nuclear hormone receptors and exist as three isoforms namely PPARα, PPARβ and PPARγ. PPARs function as key regulators of glucose and lipid metabolism and are potential targets for drugs used in the treatment of glucose and lipid metabolism dysregulation. PPARs also regulate the expression of genes involved in the process of cellular proliferation and differentiation. Since it was discovered that PPAR ligands cause liver tumourigenesis in rodents, PPARs and their modulators have been investigated widely in in vitro and in vivo studies of carcinogenesis of the liver, colon, prostate, lung and skin. PPARα and PPARγ are the most studied PPAR isoforms in relation to cancer, while the association of PPARβ with cancer is increasingly being investigated. Some studies suggest that PPARβ and its ligands may have anticancer activity, while other studies identify a role for PPARβ in tumour promotion and progression. Breast cancer is one of the most common types of cancer in women with the majority caused by non-hereditary mechanisms. The activation of PPARα in breast cancer cells is associated with an increase in proliferation, while PPARγ activation in breast cancer cells is related to differentiation and an inhibition of cell proliferation. The role of PPARβ and its modulators in breast cancer is uncertain, as there have been limited studies addressing the effects of PPARβ modulation in breast cancer cell lines. Environmental contaminants such as the phthalate plasticizers and alcohol are putative risk factors for breast cancer. The phthalates di(2-ethylhexyl)phthalate (DEHP) and di-n-butyl phthalate (DBP) are plasticizers that are used in a range of common household, medical and beauty products and as a consequence humans are exposed to significant levels of these compounds. DEHP and DBP are known teratogens in rodents and DEHP induces hepatocarcinogenesis in a process thought to be mediated via PPARα. DEHP and DBP are metabolized in vivo by esterases to the monoesters, mono-(2-ethylhexyl) phthalate (MEHP) and mono-n-butyl phthalate (MBP), and these compounds have been identified in human biological samples. MEHP and MBP modulate PPARs in various tissues and cell types, but their ability to modulate PPARs in human breast cancer cells is not known. Like phthalates, ethanol is another modulator of PPARs and alcohol consumption is associated positively with breast cancer development, but the molecular mechanisms involved are unknown and there are no studies that examine the effects of ethanol and its metabolite acetaldehyde on PPARs in breast cancer cell lines. This thesis describes studies establishing and validating a breast cancer cell line that conditionally expresses human PPARβ under the control of a tetracycline regulator. Using this model, the ability of PPARβ over-expression and/or activation by the PPARβ specific ligand GW0742 to promote breast cancer cell proliferation was studied. Furthermore, putative PPARβ regulated genes were examined for alterations in expression in the presence of the PPARβ ligand. This work determined that over-expression of PPARβ and/or its activation by GW0742 does not promote proliferation in MCF-7 breast cancer cells. This thesis also investigated the effects of the phthalate monoesters MEHP and MBP on PPARs in MCF-7 breast cancer cells. It was found that MEHP activated both PPARα and PPARγ but was unable to activate PPARβ, whereas MBP could not activate any of the PPAR isoforms. MBP was an antagonist for both PPARγ and PPARβ. Using breast cancer cell lines, studies were conducted addressing the effects of an increasing concentration of ethanol (0-300 mM) on the transcription and transactivation of PPARα and PPARβ isoforms. Estrogen receptor positive MCF-7 breast cancer cells were more sensitive to the effects of ethanol than estrogen receptor negative MDA-MB-231 cells, with changes in PPARα mRNA more pronounced than PPARβ mRNA. Studies in MCF-7 cells conditionally expressing either PPARα or PPARβ in the presence of their respective specific ligands, GW7647 and GW0742, revealed that ethanol concentrations of 20 mM and 100 mM suppressed the maximal response to ligand-mediated activation for PPARα. Studies using the ethanol metabolism enzyme inhibitors 4-methylpyrazole and cyanamide, suggested that while ethanol was responsible for the modulation of PPARβ transactivation, the primary metabolite acetaldehyde was responsible for the effects on PPARα transactivation. Lastly, it was determined that ethanol and/or GW0742 did not increase the proliferation of MCF-7 Tet-off cells. The findings in this thesis suggest that given the different consequences of MEHP, MBP and ethanol on PPARs, PPAR expression and activation by ligands may have tissue specific consequences and that PPARβ may have a complex role in mammary gland tumourigenesis.

A febre é um aumento regulado da temperatura corporal central, caracterizada por uma alteração no centro termorregulatório, a qual resulta da interação entre o sistema nervoso central e o imunológico. Enquanto a febre caracteriza lesão celular, infecção e inflamação, ela tem sido considerada o mais importante componente da resposta de fase aguda. Embora existam evidências de que a febre aumenta a defesa do hospedeiro, alguns estudos têm sugerido que o aumento da temperatura central a níveis febris pode ser prejudicial. Portanto, nas situações clínicas nas quais os riscos associados com a febre superam os benefícios, o tratamento antipirético é formalmente indicado. Os derivados pirazolínicos constituem um importante grupo de compostos orgânicos que têm sido extensivamente estudados devido às suas inúmeras atividades biológicas, que incluem atividade antipirética. Recentemente uma série de derivados pirazolínicos inéditos foi avaliada quanto à atividade antiedematogênica e antinociceptiva em camundongos. Estes compostos causam antinocicepção no teste da formalina e no modelo de artrite induzida por adjuvante de Freund, bem como diminuem o edema induzido por carragenina. Dados os efeitos antiinflamatórios descritos para estes compostos, o objetivo do estudo foi investigar o efeito de oito derivados 5-trifluormetil-4,5-diidro- 1H-1-pirazol-1-carboxiamida (TFDPs) sobre a temperatura corporal basal, a febre induzida por S. cerevisiae (0.135 g/Kg, i.p.) e a inflamação peritoneal em ratos Wistar machos de 28 dias de idade. Somente os compostos 3Et- e 3Pr-TFDP (140 e 200 μmol/kg respectivamente, s.c., 4 h após a injeção do S. cerevisiae) atenuaram a febre em 61.0% e 82.4%, respectivamente. Estes dois compostos foram selecionados para a investigação dos mecanismos de ação. Os efeitos sobre a atividade da ciclooxigenase-1 e -2 (COX-1 e COX-2), a oxidação in vitro do 1,1-difenil-2- picrilhidrazil (DPPH), os níveis de TNF-a e IL-1b e influxo de leucócitos na cavidade peritoneal dos ratos injetados com S. cerevisiae foram determinados. Enquanto 3Et- e 3Pr-TFDP não alteraram o aumento nos níveis de TNF-a e IL-1b induzido por S. cerevisiae, o derivado 3Et- TFDP causou uma redução de 42% na contagem de leucócitos na cavidade peritoneal. 3Et- e 3Pr-TFDP não alteraram a atividade da COX-1 e COX-2 in vitro, mas apresentaram atividade antioxidante no ensaio do DPPH, com CI50 de 39.3 (25.0-62.0) mM e 162.9 (135.6-195.7) mM, respectivamente. Em outro grupo de experimentos, foi avaliado o efeito do pré-tratamento dos animais com os compostos 3Et- e 3Pr-TFDP sobre a inflamação peritoneal induzida por S.cerevisiae em ratos. O pré-tratamento com 3Et-TFDP (140 μmol/kg, 5 mL/Kg, s.c.) preveniu significativamente o aumento no influxo de leucócitos, a permeabilidade vascular peritoneal e a atividade da mieloperoxidase (MPO), mas não teve efeito sobre os níveis de TNF-a e IL-1b. Por outro lado, 3Pr-TFDP (200 μmol/kg, 5 mL/Kg, s.c.) não apresentou efeito sobre nenhum desses parâmetros inflamatórios. O presente estudo descreve dois novos derivados pirazolínicos com atividade antipirética, cujos mecanismos de ação não envolvem inibição da COX ou inibição da liberação de citocinas pirogênicas. Além disso, foi demonstrado que o composto 3Et-TFDP apresenta potencial antiinflamatório, atuando sobre o influxo de leucócitos, permeabilidade vascular peritoneal e aumento da atividade da MPO induzidos por S. cerevisiae. Em conjunto, nossos dados sugerem que os derivados pirazolínicos 3Et- e 3Pr-TFDP parecem ser compostos antipiréticos e antiinflamatórios promissores. / Fever is a regulated increase of body core temperature characterized by a raised thermoregulatory set point, which results from the interaction of the central nervous and immune systems. While fever is a hallmark of injury, infection and inflammation, it has also been considered the most important component of acute-phase response. Although there is evidence supporting the idea that fever enhances host defenses, some studies have suggested that raising core temperature to the febrile range may be harmful. Therefore, in the clinical situations in which fever-associated risks outweigh benefits, antipyretic treatment is formally indicated. Pyrazoles constitute an important group of organic compounds that have been extensively studied due to their numerous biological activities. Recently a series of pyrazole derivatives have been screened for antinociceptive and antiedematogenic activity in mice. These compounds cause antinociception in the formalin test and in the Freund's adjuvant (CFA) animal model of arthritis and decrease carrageenin-induced edema. Given the effects reported for these compounds, we decided to investigate the effect of eight 5-hydroxy-5-trifluoromethyl-4,5-dihydro- 1H-1-carboxyamidepyrazoles (TFDPs) on body temperature, baker´s yeast-induced fever and peritoneal inflammation in 28 days-old male Wistar rats. Only 3ethyl- and 3propyl-TFDP (140 and 200 μmol/kg, respectively, s.c., 4 h after S. cerevisiae injection) attenuated baker’s yeastinduced fever by 61.0% and 82.4%, respectively. These two effective antipyretics were selected to investigate the mechanisms of action. The effects on cyclooxygenase-1 and -2 (COX-1 and COX-2) activities, on 1,1-diphenyl-2-picrylhydrazyl (DPPH) oxidation in vitro, on TNF-a and IL- 1b levels and on leukocyte counts in the washes of peritoneal cavities of rats injected with baker’s yeast were determined. While 3ethyl- and 3propyl-TFDP did not reduce baker’s yeastinduced increases of IL-1 or TNF- levels, 3ethyl-TFDP caused a 42% reduction in peritoneal leukocyte count. 3ethyl- and 3propyl-TFDP did not alter COX-1 and COX-2 activities in vitro, but presented antioxidant activity in the DPPH assay with an IC50 of 39.3 (25.0-62.0) mM and 162.9 (135.6-195.7) mM, respectively. In a other set of the experiments, we investigate the effect of 3- ethyl- and 3-propyl-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-carboxyamidepyrazoles on S.cerevisiae-induced peritoneal inflammation in rats. Pre-treatment with 3ethyl-TFDP (140 μmol/kg, 5 mL/Kg) significantly prevented S.cerevisiae-induced increase in leukocyte influx, peritoneal vascular permeability and myeloperoxidase activity, but had no effect on TNF-a and IL-1b levels. On the other hand, 3propyl-TFDP (200 μmol/kg, 5 mL/Kg) had no effect on these inflammatory parameters. The current study describes two novel antipyretic pyrazole derivatives, whose mechanisms of action do not involve the classic inhibition of the COX pathway or pyrogenic cytokine release. In addition, it is shown that 3ethyl-TFDP presents antiinflammatory potential, since it reduces leukocyte influx, peritoneal vascular permeability and MPO activity. Taken together, our data suggest that the pyrazole derivatives 3ethyl- and 3propyl-TFDP seems a promising antipyretic and anti-inflammatory compounds.

A febre é um aumento regulado da temperatura corporal central, caracterizada por uma alteração no centro termorregulatório, a qual resulta da interação entre o sistema nervoso central e o imunológico. Enquanto a febre caracteriza lesão celular, infecção e inflamação, ela tem sido considerada o mais importante componente da resposta de fase aguda. Embora existam evidências de que a febre aumenta a defesa do hospedeiro, alguns estudos têm sugerido que o aumento da temperatura central a níveis febris pode ser prejudicial. Portanto, nas situações clínicas nas quais os riscos associados com a febre superam os benefícios, o tratamento antipirético é formalmente indicado. Os derivados pirazolínicos constituem um importante grupo de compostos orgânicos que têm sido extensivamente estudados devido às suas inúmeras atividades biológicas, que incluem atividade antipirética. Recentemente uma série de derivados pirazolínicos inéditos foi avaliada quanto à atividade antiedematogênica e antinociceptiva em camundongos. Estes compostos causam antinocicepção no teste da formalina e no modelo de artrite induzida por adjuvante de Freund, bem como diminuem o edema induzido por carragenina. Dados os efeitos antiinflamatórios descritos para estes compostos, o objetivo do estudo foi investigar o efeito de oito derivados 5-trifluormetil-4,5-diidro- 1H-1-pirazol-1-carboxiamida (TFDPs) sobre a temperatura corporal basal, a febre induzida por S. cerevisiae (0.135 g/Kg, i.p.) e a inflamação peritoneal em ratos Wistar machos de 28 dias de idade. Somente os compostos 3Et- e 3Pr-TFDP (140 e 200 μmol/kg respectivamente, s.c., 4 h após a injeção do S. cerevisiae) atenuaram a febre em 61.0% e 82.4%, respectivamente. Estes dois compostos foram selecionados para a investigação dos mecanismos de ação. Os efeitos sobre a atividade da ciclooxigenase-1 e -2 (COX-1 e COX-2), a oxidação in vitro do 1,1-difenil-2- picrilhidrazil (DPPH), os níveis de TNF-a e IL-1b e influxo de leucócitos na cavidade peritoneal dos ratos injetados com S. cerevisiae foram determinados. Enquanto 3Et- e 3Pr-TFDP não alteraram o aumento nos níveis de TNF-a e IL-1b induzido por S. cerevisiae, o derivado 3Et- TFDP causou uma redução de 42% na contagem de leucócitos na cavidade peritoneal. 3Et- e 3Pr-TFDP não alteraram a atividade da COX-1 e COX-2 in vitro, mas apresentaram atividade antioxidante no ensaio do DPPH, com CI50 de 39.3 (25.0-62.0) mM e 162.9 (135.6-195.7) mM, respectivamente. Em outro grupo de experimentos, foi avaliado o efeito do pré-tratamento dos animais com os compostos 3Et- e 3Pr-TFDP sobre a inflamação peritoneal induzida por S.cerevisiae em ratos. O pré-tratamento com 3Et-TFDP (140 μmol/kg, 5 mL/Kg, s.c.) preveniu significativamente o aumento no influxo de leucócitos, a permeabilidade vascular peritoneal e a atividade da mieloperoxidase (MPO), mas não teve efeito sobre os níveis de TNF-a e IL-1b. Por outro lado, 3Pr-TFDP (200 μmol/kg, 5 mL/Kg, s.c.) não apresentou efeito sobre nenhum desses parâmetros inflamatórios. O presente estudo descreve dois novos derivados pirazolínicos com atividade antipirética, cujos mecanismos de ação não envolvem inibição da COX ou inibição da liberação de citocinas pirogênicas. Além disso, foi demonstrado que o composto 3Et-TFDP apresenta potencial antiinflamatório, atuando sobre o influxo de leucócitos, permeabilidade vascular peritoneal e aumento da atividade da MPO induzidos por S. cerevisiae. Em conjunto, nossos dados sugerem que os derivados pirazolínicos 3Et- e 3Pr-TFDP parecem ser compostos antipiréticos e antiinflamatórios promissores. / Fever is a regulated increase of body core temperature characterized by a raised thermoregulatory set point, which results from the interaction of the central nervous and immune systems. While fever is a hallmark of injury, infection and inflammation, it has also been considered the most important component of acute-phase response. Although there is evidence supporting the idea that fever enhances host defenses, some studies have suggested that raising core temperature to the febrile range may be harmful. Therefore, in the clinical situations in which fever-associated risks outweigh benefits, antipyretic treatment is formally indicated. Pyrazoles constitute an important group of organic compounds that have been extensively studied due to their numerous biological activities. Recently a series of pyrazole derivatives have been screened for antinociceptive and antiedematogenic activity in mice. These compounds cause antinociception in the formalin test and in the Freund's adjuvant (CFA) animal model of arthritis and decrease carrageenin-induced edema. Given the effects reported for these compounds, we decided to investigate the effect of eight 5-hydroxy-5-trifluoromethyl-4,5-dihydro- 1H-1-carboxyamidepyrazoles (TFDPs) on body temperature, baker´s yeast-induced fever and peritoneal inflammation in 28 days-old male Wistar rats. Only 3ethyl- and 3propyl-TFDP (140 and 200 μmol/kg, respectively, s.c., 4 h after S. cerevisiae injection) attenuated baker’s yeastinduced fever by 61.0% and 82.4%, respectively. These two effective antipyretics were selected to investigate the mechanisms of action. The effects on cyclooxygenase-1 and -2 (COX-1 and COX-2) activities, on 1,1-diphenyl-2-picrylhydrazyl (DPPH) oxidation in vitro, on TNF-a and IL- 1b levels and on leukocyte counts in the washes of peritoneal cavities of rats injected with baker’s yeast were determined. While 3ethyl- and 3propyl-TFDP did not reduce baker’s yeastinduced increases of IL-1 or TNF- levels, 3ethyl-TFDP caused a 42% reduction in peritoneal leukocyte count. 3ethyl- and 3propyl-TFDP did not alter COX-1 and COX-2 activities in vitro, but presented antioxidant activity in the DPPH assay with an IC50 of 39.3 (25.0-62.0) mM and 162.9 (135.6-195.7) mM, respectively. In a other set of the experiments, we investigate the effect of 3- ethyl- and 3-propyl-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-carboxyamidepyrazoles on S.cerevisiae-induced peritoneal inflammation in rats. Pre-treatment with 3ethyl-TFDP (140 μmol/kg, 5 mL/Kg) significantly prevented S.cerevisiae-induced increase in leukocyte influx, peritoneal vascular permeability and myeloperoxidase activity, but had no effect on TNF-a and IL-1b levels. On the other hand, 3propyl-TFDP (200 μmol/kg, 5 mL/Kg) had no effect on these inflammatory parameters. The current study describes two novel antipyretic pyrazole derivatives, whose mechanisms of action do not involve the classic inhibition of the COX pathway or pyrogenic cytokine release. In addition, it is shown that 3ethyl-TFDP presents antiinflammatory potential, since it reduces leukocyte influx, peritoneal vascular permeability and MPO activity. Taken together, our data suggest that the pyrazole derivatives 3ethyl- and 3propyl-TFDP seems a promising antipyretic and anti-inflammatory compounds.