Synthesis and Biological Evaluation of Natural-Product-Inspired, Aminoalkyl-Substituted 1-Benzopyrans as Novel Antiplasmodial Agents.

Herein, relationships between the structures of 1-aminoethyl-substituted chromenes and their antimalarial activities were thoroughly investigated. At first, the methyl moiety in the side chain was removed to eliminate chirality. The hydrogenation state of the benzopyran system, the position of the phenolic OH moiety, and the distance of the basic amino moiety toward both aromatic rings were varied systematically. 1-Benzopyran-5-ol 8b (IC50 = 10 nM), 1-benzopyran-7-ol 9c (IC50 = 38 nM), and the aminoalcohol 19c (IC50 = 17 nM) displayed antiplasmodial activity with IC50 values below 50 nM. To identify the mechanism of action, inhibition of three key enzymes by 9c was investigated. 9c was not able to reduce the number of Plasmodia in erythrocytes of mice. This low in vivo activity was explained by fast clearance from blood plasma combined with rapid biotransformation of 9c. Three main metabolites of 9c were identified by liquid chromatography-mass spectrometry (LC-MS) methods.

Comparative study between the anti-P. falciparum activity of triazolopyrimidine, pyrazolopyrimidine and quinoline derivatives and the identification of new PfDHODH inhibitors.

In this work, we designed and synthesized 35 new triazolopyrimidine, pyrazolopyrimidine and quinoline derivatives as P. falciparum inhibitors (3D7 strain). Thirty compounds exhibited anti-P. falciparum activity, with IC50 values ranging from 0.030 to 9.1 µM. The [1,2,4]triazolo[1,5-a]pyrimidine derivatives were more potent than the pyrazolo[1,5-a]pyrimidine and quinoline analogues. Compounds 20, 21, 23 and 24 were the most potent inhibitors, with IC50 values in the range of 0.030-0.086 µM and were equipotent to chloroquine. In addition, the compounds were selective, showing no cytotoxic activity against the human hepatoma cell line HepG2. All [1,2,4]triazolo[1,5-a]pyrimidine derivatives inhibited PfDHODH activity in the low micromolar to low nanomolar range (IC50 values of 0.08-1.3 µM) and did not show significant inhibition against the HsDHODH homologue (0-30% at 50 µM). Molecular docking studies indicated the binding mode of [1,2,4]triazolo[1,5-a]pyrimidine derivatives to PfDHODH, and the highest interaction affinities for the PfDHODH enzyme were in agreement with the in vitro experimental evaluation. Thus, the most active compounds against P. falciparum parasites 20 (R = CF3, R1 = F; IC50 = 0.086 µM), 21 (R = CF3; R1 = CH3; IC50 = 0.032 µM), 23, (R = CF3, R1 = CF3; IC50 = 0.030 µM) and 24 (R = CF3, 2-naphthyl; IC50 = 0.050 µM) and the most active inhibitor against PfDHODH 19 (R = CF3, R1 = Cl; IC50 = 0.08 µM - PfDHODH) stood out as new lead compounds for antimalarial drug discovery. Their potent in vitro activity against P. falciparum and the selective inhibition of the PfDHODH enzyme strongly suggest that this is the mechanism of action underlying this series of new [1,2,4]triazolo[1,5-a]pyrimidine derivatives.

Discovery of Antimalarial Azetidine-2-carbonitriles That Inhibit P. falciparum Dihydroorotate Dehydrogenase.

Dihydroorotate dehydrogenase (DHODH) is an enzyme necessary for pyrimidine biosynthesis in protozoan parasites of the genus Plasmodium, the causative agents of malaria. We recently reported the identification of novel compounds derived from diversity-oriented synthesis with activity in multiple stages of the malaria parasite life cycle. Here, we report the optimization of a potent series of antimalarial inhibitors consisting of azetidine-2-carbonitriles, which we had previously shown to target P. falciparum DHODH in a biochemical assay. Optimized compound BRD9185 (27) has in vitro activity against multidrug-resistant blood-stage parasites (EC50 = 0.016 µM) and is curative after just three doses in a P. berghei mouse model. BRD9185 has a long half-life (15 h) and low clearance in mice and represents a new structural class of DHODH inhibitors with potential as antimalarial drugs.

Lapachol, a compound targeting pyrimidine metabolism, ameliorates experimental autoimmune arthritis.

BACKGROUND: The inhibition of pyrimidine biosynthesis by blocking the dihydroorotate dehydrogenase (DHODH) activity, the prime target of leflunomide (LEF), has been proven to be an effective strategy for rheumatoid arthritis (RA) treatment. However, a considerable proportion of RA patients are refractory to LEF. Here, we investigated lapachol (LAP), a natural naphthoquinone, as a potential DHODH inhibitor and addressed its immunosuppressive properties. METHODS: Molecular flexible docking studies and bioactivity assays were performed to determine the ability of LAP to interact and inhibit DHODH. In vitro studies were conducted to assess the antiproliferative effect of LAP using isolated lymphocytes. Finally, collagen-induced arthritis (CIA) and antigen-induced arthritis (AIA) models were employed to address the anti-arthritic effects of LAP. RESULTS: We found that LAP is a potent DHODH inhibitor which had a remarkable ability to inhibit both human and murine lymphocyte proliferation in vitro. Importantly, uridine supplementation abrogated the antiproliferative effect of LAP, supporting that the pyrimidine metabolic pathway is the target of LAP. In vivo, LAP treatment markedly reduced CIA and AIA progression as evidenced by the reduction in clinical score, articular tissue damage, and inflammation. CONCLUSIONS: Our findings propose a binding model of interaction and support the ability of LAP to inhibit DHODH, decreasing lymphocyte proliferation and attenuating the severity of experimental autoimmune arthritis. Therefore, LAP could be considered as a potential immunosuppressive lead candidate with potential therapeutic implications for RA.

Evaluation of 7-arylaminopyrazolo[1,5-a]pyrimidines as anti-Plasmodium falciparum, antimalarial, and Pf-dihydroorotate dehydrogenase inhibitors.

Malaria remains one of the most serious global infectious diseases. An important target for antimalarial chemotherapy is the enzyme dihydroorotate dehydrogenase from Plasmodium falciparum (PfDHODH), which is responsible for the conversion of dihydroorotate to orotate in the de novo pyrimidine biosynthetic pathway. In this study, we have designed and synthesized fifteen 7-arylpyrazolo[1,5-a]pyrimidine derivatives using ring bioisosteric replacement and molecular hybridization of functional groups based on the highly active 5-methyl-N-(naphthalen-2-yl)-2-(trifluoromethyl)- [1,2,4]triazolo[1,5-a]pyrimidin-7-amine. The compounds were tested against Plasmodium falciparum, as antimalarials in mice with P. berghei, and as inhibitors of PfDHODH. Thirteen compounds were found to be active against P. falciparum, with IC50 values ranging from 1.2 ± 0.3 to 92 ± 26 µM in the anti-HRP2 and hypoxanthine assays. Four compounds showed the highest selective index (SI), which is a ratio between cytotoxicity and activity in vitro. The inhibition of PfDHODH showed that compound 30 (R2 = CH3; R5 = CF3; Ar = 7-ß-naphthyl) displayed higher and selective inhibitory activity, with IC50 = 0.16 ± 0.01 µM, followed by 25 (R2 = CH3; R5 = CH3; Ar = 7-ß-Naphthyl) and 19 (R2 = CF3; R5 = CF3; Ar = 7-ß-naphthyl), with IC50 = 4 ± 1 µM and 6 ± 1 µM, respectively. The trifluoromethyl group at the 2- or 5-positions of the pyrazolo[1,5-a]pyrimidine ring led to increased drug activity. The docking results agreed with the values obtained from enzymatic assays.

Dipyrone metabolite 4-MAA induces hypothermia and inhibits PGE2 -dependent and -independent fever while 4-AA only blocks PGE2 -dependent fever.

BACKGROUND AND PURPOSE: The antipyretic and hypothermic prodrug dipyrone prevents PGE2 -dependent and -independent fever induced by LPS from Escherichia coli and Tityus serrulatus venom (Tsv) respectively. We aimed to identify the dipyrone metabolites responsible for the antipyretic and hypothermic effects. EXPERIMENTAL APPROACH: Male Wistar rats were treated i.p. with indomethacin (2 mg·kg(-1) ), dipyrone, 4-methylaminoantipyrine (4-MAA), 4-aminoantipyrine (4-AA) (60-360 mg·kg(-1) ), 4-formylaminoantipyrine, 4-acethylaminoantipyrine (120-360 mg·kg(-1) ) or vehicle 30 min before i.p. injection of LPS (50 µg·kg(-1) ), Tsv (150 µg·kg(-1) ) or saline. Rectal temperatures were measured by tele-thermometry and dipyrone metabolite concentrations determined in the plasma, CSF and hypothalamus by LC-MS/MS. PGE2 concentrations were determined in the CSF and hypothalamus by elisa. KEY RESULTS: In contrast to LPS, Tsv-induced fever was not followed by increased PGE2 in the CSF or hypothalamus. The antipyretic time-course of 4-MAA and 4-AA on LPS-induced fever overlapped with the period of the highest concentrations of 4-MAA and 4-AA in the hypothalamus, CSF and plasma. These metabolites reduced LPS-induced fever and the PGE2 increase in the plasma, CSF and hypothalamus. Only 4-MAA inhibited Tsv-induced fever. The higher doses of dipyrone and 4-MAA also induced hypothermia. CONCLUSIONS AND IMPLICATIONS: The presence of 4-MAA and 4-AA in the CSF and hypothalamus was associated with PGE2 synthesis inhibition and a decrease in LPS-induced fever. 4-MAA was also shown to be an antipyretic metabolite for PGE2 -independent fever induced by Tsv suggesting that it is responsible for the additional antipyretic mechanism of dipyrone. Moreover, 4-MAA is the hypothermic metabolite of dipyrone.

Simultaneous determination of dipyrone metabolites in rat hypothalamus, cerebrospinal fluid and plasma samples by LC-MS/MS.

BACKGROUND: After oral administration dipyrone is rapidly hydrolyzed to 4-methylaminoantipyrine, which is absorbed and further metabolized to 4-formylaminoantipyrine and to 4-aminoantipyrine, which is acetylated by a polymorphic N-acetyltransferase system to 4-acetylaminoantipyrine. To evaluate the presence of dipyrone metabolites in different rat matrices after intraperitoneal administration, an analytical method was developed and validated. METHODOLOGY: The four main dipyrone metabolites were extracted from plasma, cerebrospinal fluid and hypothalamus samples by LLE prior to LC-MS/MS. RESULTS: Standard calibration graphs for all metabolites were linear (r > 0.99). The intra- and inter-day precision and accuracy values were both inferior to 15%. CONCLUSION: This method is simple and specific for studying dipyrone metabolites after intraperitoneal administration.

Enantioselective analysis of zopiclone in rat brain by liquid chromatography tandem mass spectrometry.

A new high-performance liquid chromatographic method with triple quadrupole mass spectrometry detection was developed and validated for the quantification of zopiclone enantiomers in rat brain samples. Zopiclone enantiomers were resolved on a CHIRALPAK AD column with a mobile phase consisting of acetonitrile/ethanol/methanol (60:20:20, v/v/v) at a flow rate of 1.3 mL min(-1). Moclobemide was used as internal standard. The sample treatment procedure was carried out employing solid-phase extraction, yielding mean absolute recoveries of 89.6 and 91.7% for each zopiclone enantiomer. The validated method showed linearity in the range of 0.29-344.8 ng g(-1), with quantification limits of 0.29 ng g(-1) for both enantiomers. Precision and accuracy were within acceptable levels of confidence (<15%). The method was applied in a pilot study of zopiclone kinetic disposition in rats. It could be observed that the levels of (+)-(S)-zopiclone were always higher than those of (-)-(R)-zopiclone, confirming the stereoselective disposition of zopiclone.

Fluoxetine induces preventive and complex effects against colon cancer development in epithelial and stromal areas in rats.

Fluoxetine (FLX) is a drug commonly used as antidepressant. However, its effects on tumorigenesis remain controversial. Aiming to evaluate the effects of FLX treatment on early malignant changes, we analyzed serotonin (5-HT) metabolism and recognition, aberrant crypt foci (ACF), proliferative process, microvessels, vascular endothelial growth factor (VEGF), and cyclooxygenase-2 (COX-2) expression in colon tissue. Male Wistar rats received a daily FLX-gavage (30mgkg(-1)) and, a single dose of 1,2 dimethylhydrazine (DMH; i.p., 125mgkg(-1)). After 6 weeks of FLX-treatment, our results revealed that FLX and nor-fluoxetine (N-FLX) are present in colon tissue, which was related to significant increase in serotonin (5-HT) levels (P<0.05) possibly through a blockade in SERT mRNA (serotonin reuptake transporter; P<0.05) resulting in lower 5-hydroxyindoleacetic acid (5-HIAA) levels (P<0.01) and, 5-HT2C receptor mRNA expressions. FLX-treatment decreased dysplastic ACF development (P<0.01) and proliferative process (P<0.001) in epithelia. We observed a significant decrease in the development of malignant microvessels (P<0.05), VEGF (P<0.001), and COX-2 expression (P<0.01). These findings suggest that FLX may have oncostatic effects on carcinogenic colon tissue, probably due to its modulatory activity on 5-HT metabolism and/or its ability to reduce colonic malignant events.

Enantioselective analysis of zopiclone and its metabolites in plasma by liquid chromatography/tandem mass spectrometry.

A high-performance liquid chromatographic method with triple-quadrupole mass spectrometry detection (LC-MS-MS) was developed and validated for the first time for the simultaneous quantification of zopiclone and its metabolites in rat plasma samples. The analytes were isolated from rat plasma by liquid-liquid extraction and separated using a chiral stationary phase based on an amylose derivative, Chiralpak ADR-H column, and ethanol-methanol-acetonitrile (50:45:5, v/v/v) plus 0.025% diethylamine as the mobile phase, at a flow-rate of 1.0 mL min(-1). Moclobemide was used as the internal standard. The developed method was linear over the concentration range of 7.5-500 ng mL(-1). The mean absolute recoveries were 74.6 and 75.7; 61.6 and 56.9; 72.5, and 70.7 for zopiclone enantiomers, for N-desmethyl zopiclone enantiomers and for zopiclone-N-oxide enantiomers, respectively, and 75.9 for the internal standard. Precision and accuracy were within acceptable levels of confidence (<15%). The method application in a pilot study of zopiclone kinetic disposition in rats showed that the levels of (+)-(S)-zopiclone were always higher than those of (-)-R-zopiclone. Higher concentrations were also observed for (+)-(S)-N-desmethyl zopiclone and (+)-(S)-N-oxide zopiclone, confirming the stereoselective disposition of zopiclone.

Determination of beta-artemether and its main metabolite dihydroartemisinin in plasma employing liquid-phase microextraction prior to liquid chromatographic-tandem mass spectrometric analysis.

A method for the determination of artemether (ART) and its main metabolite dihydroartemisinin (DHA) in plasma employing liquid-phase microextraction (LPME) for sample preparation prior to liquid chromatography-tandem mass spectrometry (LC-MS-MS) was developed. The analytes were extracted from 1mL of plasma utilizing a two-phase LPME procedure with artemisinin as internal standard. Using the optimized LPME conditions, mean absolute recovery rates of 25 and 32% for DHA and ART, respectively, were achieved using toluene-n-octanol (1:1, v/v) as organic phase with an extraction time of 30min. After extraction, the analytes were resolved within 5min using a mobile phase consisting of methanol-ammonium acetate (10mmolL(-1), pH 5.0, 80:20, v/v) on a laboratory-made column based on poly(methyltetradecylsiloxane) attached to a zirconized-silica support. MS-MS detection was employed using an electrospray interface in the positive ion mode. The method developed was linear over the range of 5-1000ngmL(-1) for both analytes. Precision and accuracy were within acceptable levels of confidence (<15%). The assay was applied to the determination of these analytes in plasma from rats treated with ART. The two-phase LPME procedure is affordable and the solvent consumption was very low compared to the traditional methods of sample preparation.

A highly sensitive LC-MS-MS assay for analysis of midazolam and its major metabolite in human plasma: applications to drug metabolism.

The present report describes a rapid, selective and a highly sensitive assay for midazolam (MDZ) and its major metabolite 1-hydroxymidazolam (1-OH-MDZ) in human plasma employing liquid chromatography-tandem mass spectrometry (LC-MS-MS) detection. The method involves liquid-liquid extraction sample clean-up, separation on a Purospher RP 18-e column and detection with an electrospray interface in the positive ion mode. The overall recoveries were about 100% and 80% for midazolam and 1-hydroxymidazolam, respectively. Accuracy, precision and linearity were acceptable for biological samples with quantitation limits of 0.1-100 ng mL(-1) plasma for both analytes. The validated method was successfully applied to quantify plasma concentration of midazolam and 1-hydroxymidazolam in authentic samples from a healthy volunteer following a single 15 mg oral dose of midazolam (apparent total clearance: 3.47 L h(-1)kg(-1) and AUC(0-alpha)IOH-MDZ/MDZ: 0.338).

Enantioselective analysis of ibuprofen in human plasma by anionic cyclodextrin-modified electrokinetic chromatography.

This paper reports the development of a rapid method for the enantioselective analysis of the nonsteroidal anti-inflammatory drug ibuprofen in human plasma by capillary electrophoresis employing the anionic cyclodextrin-modified electrokinetic chromatography mode. Sample cleanup was carried out by acidification with HCl followed by liquid-liquid extraction with hexane:isopropanol (99:1 v/v). The complete enantioselective analysis was performed within 10 min, using 100 mmol L(-1) phosphoric acid/triethanolamine buffer, pH 2.6, containing 2.0% w/v sulfated beta-cyclodextrin as chiral selector; fenoprofen, another nonsteroidal anti-inflammatory drug, was used as internal standard. The calibration curves were linear over the concentration range of 0.25-125.0 microg mL(-1) for each enantiomer of ibuprofen. The mean recoveries for ibuprofen enantiomers were up to 85%. The enantiomers studied could be quantified at three different concentrations (0.5, 5.0 and 50.0 microg mL(-1)) with a coefficient of variation and relative error not higher than 15%. The quantitation limit was 0.2 microg mL(-1) for (+)-(S)- and (-)-(R)-ibuprofen using 1 mL of human plasma. The plasma endogenous compounds and other drugs did not interfere with the present assay. The analysis of real plasma samples obtained from a healthy volunteer after administration of 600 mg of racemic ibuprofen showed a maximum plasma level of 29.6 and 39.9 microg mL(-1) of (-)-(R)- and (+)-(S)-ibuprofen, respectively, and the area under plasma concentration-time curve AUC(0-infinity) (+)-(S)/AUC(0-infinity) (-)-(R) ratio was 1.87.