Myclobutanil enantioselective risk assessment in humans through in vitro CYP450 reactions: Metabolism and inhibition studies.

Myclobutanil is a chiral triazole fungicide that is employed worldwide. Although enantiomers have the same physical-chemical properties, they may differ in terms of activity, metabolism, and toxicity. This investigation consisted of in vitro enantioselective metabolism studies that employed a human model to assess the risks of myclobutanil in humans. A LC-MS/MS enantioselective method was developed and validated. The enzymatic kinetic parameters (VMAX, KMapp, and CLINT) determined for in vitro rac-myclobutanil and S-(+)-myclobutanil metabolism revealed enantioselective differences. Furthermore, human CYP450 enzymes did not metabolize R-(-)-myclobutanil. The predicted in vivo toxicokinetic parameters indicated that S-(+)-myclobutanil may be preferentially eliminated by the liver and suffer the first-pass metabolism effect. However, because CYP450 did not metabolize R-(-)-myclobutanil, this enantiomer could reach the systemic circulation and stay longer in the human body, potentially causing toxic effects. The CYP450 isoforms CYP2C19 and CYP3A4 were involved in rac-myclobutanil and S-(+)-myclobutanil metabolism. Although there were differences in the metabolism of the myclobutanil enantiomers, in vitro inhibition studies did not show significant enantioselective differences. Overall, the present investigation suggested that myclobutanil moderately inhibits CYP2D6 and CYP2C9 in vitro and strongly inhibits CYP3A and CYP2C19 in vitro. These results provide useful scientific information for myclobutanil risk assessment in humans.

Pre-clinical evaluation of quinoxaline-derived chalcones in tuberculosis.

New effective compounds for tuberculosis treatment are needed. This study evaluated the effects of a series of quinoxaline-derived chalcones against laboratorial strains and clinical isolates of M. tuberculosis. Six molecules, namely N5, N9, N10, N15, N16, and N23 inhibited the growth of the M. tuberculosis H37Rv laboratorial strain. The three compounds (N9, N15 and N23) with the lowest MIC values were further tested against clinical isolates and laboratory strains with mutations in katG or inhA genes. From these data, N9 was selected as the lead compound for further investigation. Importantly, this chalcone displayed a synergistic effect when combined with moxifloxacin. Noteworthy, the anti-tubercular effects of N9 did not rely on inhibition of mycolic acids synthesis, circumventing important mechanisms of resistance. Interactions with cytochrome P450 isoforms and toxic effects were assessed in silico and in vitro. The chalcone N9 was not predicted to elicit any mutagenic, genotoxic, irritant, or reproductive effects, according to in silico analysis. Additionally, N9 did not cause mutagenicity or genotoxicity, as revealed by Salmonella/microsome and alkaline comet assays, respectively. Moreover, N9 did not inhibit the cytochrome P450 isoforms CYP3A4/5, CYP2C9, and CYP2C19. N9 can be considered a potential lead molecule for development of a new anti-tubercular therapeutic agent.

Leishmanicidal Effects of Piperlongumine (Piplartine) and Its Putative Metabolites.

Piperlongumine is an amide alkaloid found in Piperaceae species that shows a broad spectrum of biological properties, including antitumor and antiparasitic activities. Herein, the leishmanicidal effect of piperlongumine and its derivatives produced by a biomimetic model using metalloporphyrins was investigated. The results showed that IC50 values of piperlongumine in promastigote forms of Leishmania infantum and Leishmania amazonensis were 7.9 and 3.3 µM, respectively. The IC50 value of piperlongumine in the intracellular amastigote form of L. amazonensis was 0.4 µM, with a selectivity index of 25. The piperlongumine biomimetic derivatives, Ma and Mb, also showed leishmanicidal effects. We also carried out an in vitro metabolic degradation study showing that Ma is the most stable piperlongumine derivative in rat liver microsome incubations. The results presented here indicate that piperlongumine is a potential leishmanicidal candidate and support the biomimetic approach for development of new antileishmanial derivatives.

Method validation and nanoparticle characterization assays for an innovative amphothericin B formulation to reach increased stability and safety in infectious diseases.

Drug Delivery Systems (DDS) of known drugs are prominent candidates towards new and more-effective treatments of various infectious diseases as they may increase drug bioavailability, control drug delivery and target the site of action. In this sense, the encapsulation of Amphotericin B (AmB) in Nanostructured Lipid Carriers (NLCs) designed with pH-sensible phospholipids to target infectious tissues was proposed and suitable analytical methods were validated, as well as, proper nanoparticle characterization were conducted. Characterization assays by Dinamic Light Scattering (DLS) and Atomic Force Microscopy demonstrated spherical particles with nanometric size 268.0±11.8nm and Zeta Potential -42.5±1.5mV suggestive of important stability. DSC/TGA and FT-IR assessments suggested mechanical encapsulation of AmB. The AmB aggregation study indicated that the encapsulation provided AmB at the lowest cytotoxic form, polyaggregate. Analytical methods were developed and validated according to regulatory agencies in order to fast and assertively determine AmB in nanoparticle suspension and, in Drug Encapsulation Efficiency (EE%), release and stability studies. The quantification method for AmB in NLC suspension presented linearity in 5.05-60.60µgmL-1 range (y=0.07659x+0.05344) and for AmB in receptor solution presented linearity in 0.15-10.00µgmL-1 range (y=54609x+263.1), both with r≥0.999. EE% was approximately 100% and according to the release results, at pH 7.4, a sustained controlled profile was observed for up 46h. In the meantime, a micellar AmB solution demonstrated an instability pattern after 7h of contact with the medium. Degradation and release studies under acid conditions (infectious condition) firstly depicted a prominent degradation of AmB (raw-material), with 20.3±3.5% at the first hour, reaching 43.3±7.0% after 7h of study. Next, particles faster disruption in acid environment was evidenced by measuring the NLC size variation by DLS and by the loss of the bluish sheen, characteristic of the nanostructured system macroscopically observed. Finally, safety studies depicted that NLC-AmB presented reduced toxicity in fibroblast cells, corroborating with AmB aggregated form study. Therefore, an innovative AmB formulation was fully characterized and it is a new proposal for in vivo investigations.

In Vitro Inhibition of Human CYP450s 1A2, 2C9, 3A4/5, 2D6 and 2E1 by Grandisin.

Grandisin, a lignan isolated from many species of plants, such as Virola surinamensis, is a potential drug candidate due to its biological properties, highlighted by its antitumor and trypanocidal activities. In this study, the inhibitory effects of grandisin on the activities of human cytochrome P450 enzymes were investigated by using human liver microsomes. Results showed that grandisin is a competitive inhibitor of CYP2C9 and a competitive and mechanism-based inhibitor of CYP3A4/5. The apparent Ki value for CYP2C9 was 50.60 µM and those for CYP3A4/5 were 48.71 µM and 31.25 µM using two different probe substrates, nifedipine and midazolam, respectively. The apparent KI, kinact, and kinact/KI ratio for the mechanism-based inhibition of CYP3A4/5 were 6.40 µM, 0.037 min-1, and 5.78 mL ·â€Šmin-1 µmol-1, respectively, by examining nifedipine oxidation, and 31.53 µM, 0.049 min-1, and 1.55 mL ·â€Šmin-1 µmol-1, respectively, by examining midazolam 1'-hydroxylation. These apparent kinact/KI values were comparable to or even higher than those for several therapeutic drugs that act as mechanism-based inhibitors of CYP3A4/5. CYP1A2 and CYP2D6 activities, in turn, were not substantially inhibited by grandisin (IC50 > 200 µM and 100 µM, respectively). In contrast, from a concentration of 4 µM, grandisin significantly stimulated CYP2E1 activity. These results improve the prediction of grandisin-drug interactions, suggesting that the risk of interactions with drugs metabolized by CYP3A4/5 and CYP2E1 cannot be overlooked.

Pharmacokinetic properties, in vitro metabolism and plasma protein binding of govaniadine an alkaloid isolated from Corydalis govaniana Wall.

Govaniadine (GOV) is an alkaloid isolated from Corydalis govaniana Wall. It has been reported to show a different number of biological activities including anti-urease, leishmanicidal and antinociceptive. The present study aims to characterize the GOV in vitro metabolism after incubation with rat and human liver microsomes (RLM and HLM, respectively) and to evaluate its pharmacokinetic properties. The identification of GOV metabolites was conducted by different mass analyzers: a micrOTOF II-ESI-ToF Bruker Daltonics® and an amaZon-SL ion trap (IT) Bruker Daltonics®. For the pharmacokinetic study of GOV in rats after intravenous administration, a LC-MS/MS method was developed and applied to. The analyses were performed using an Acquity UPLC® coupled to an Acquity TQD detector equipped with an ESI interface. The liver microsomal incubation resulted in new O-demethylated, di-hydroxylated and mono-hydroxylated compounds. Regarding the method validation, the calibration curve was linear over the concentration range of 2.5-3150.0ngmL-1, with a lower limit of quantitation (LLOQ) of 2.5ngmL-1. This method was successfully applied to a pharmacokinetic study. The profile was best fitted to a two-compartment model, the first phase with a high distribution rate constant (α) 0.139±0.086min-1, reflected by the short distribution half-life (t1/2α) 9.2±8.9min and the later one, with an elimination half-life (t1/2ß) 55.1±37.9min. The main plasma protein binding was 96.1%. This is a first report in this field and it will be useful for further development of govaniadine as a drug candidate.

Metabolic profile and safety of piperlongumine.

Piperlongumine (PPL), a natural plant product, has been extensively studied in cancer treatment going up on clinical trials. Since the first report related to its use on cancer research (in 2011) around 80 papers have been published in less than 10 years, but a gap still remaining. There are no metabolism studies of PPL in human organism. For the lack of a better view, here, the CYP450 in vitro oxidation of PPL was described for the first time. In addition, the enzymatic kinetic data, the predicted in vivo parameters, the produced metabolites, the phenotyping study and possible piperlongumine-drug interactions in vivo is presented.

In vitro metabolism of monensin A: microbial and human liver microsomes models.

1. Monensin A, an important antibiotic ionophore that is primarily employed to treat coccidiosis, selectively complexes and transports sodium cations across lipid membranes and displays a variety of biological properties. 2. In this study, we evaluated the fungi Cunninghamella echinulata var. elegans ATCC 8688A, Cunninghamella elegans NRRL 1393 ATCC 10028B and human hepatic microsomes as CYP-P450 models to investigate the in vitro metabolism of monensin A and compare the products with the metabolites produced in vivo. 3. Mass spectrometry analysis of the products from these model systems revealed the formation of three metabolites: 3-O-demethyl monensin A, 12-hydroxy monensin A and 12-hydroxy-3-O-demethyl monensin A. We identified these products by tandem mass spectrometry and through comparison with the in vivo metabolites. 4. This analysis demonstrated that the model systems produce the same metabolites found in in vivo studies, thus they could be used to predict the metabolism of monensin A. Furthermore, we verified that liquid chromatography coupled to mass spectrometry is a powerful tool to study the in vitro metabolism of drugs, because it allows the successful identifications of several derivatives from different metabolic models.

Enantioselective fungal biotransformation of risperidone in liquid culture medium by capillary electrophoresis and hollow fiber liquid-phase microextraction.

Knowing that microbial transformations of compounds play vital roles in the preparation of new derivatives with biological activities, risperidone and its chiral metabolites were determined by capillary electrophoresis and hollow fiber liquid-phase microextraction after a fungal biotransformation study in liquid culture medium. The analytes were extracted from 1 mL liquid culture medium into 1-octanol impregnated in the pores of the hollow fiber, and into an acid acceptor solution inside the polypropylene hollow fiber. The electrophoretic separations were carried out in 100 mmol/L sodium phosphate buffer pH 3.0 containing 2.0% w/v sulfated-α-CD and carboxymethyl-ß-CD 0.5% w/v with a constant voltage of -10 kV. The method was linear over the concentration range of 100-5000 ng/mL for risperidone and 50-5000 ng/mL for each metabolite enantiomer. Within-day and between-day assay precisions and accuracies for all the analytes were studied at three concentration levels, and the values of relative standard deviation and relative error were lower than 15%. The developed method was applied in a pilot biotransformation study employing risperidone as the substrate and the filamentous fungus Mucor rouxii. This study showed that the filamentous fungus was able to metabolize risperidone enantioselectively into its chiral active metabolite, (-)-9-hydroxyrisperidone.