Redox processes are important in chemistry, with applications in biomedicine, chemical analysis, among others. As many redox experiments are also performed at a fixed value of pH, having an efficient computational method to support experimental measures at both constant redox potential and pH is very important. Such computational techniques have the potential to validate experimental observations performed under these conditions and to provide additional information unachievable experimentally such as an atomic level description of macroscopic measures. We present the implementation of discrete redox and protonation states methods for constant redox potential Molecular Dynamics (CEMD), for coupled constant pH and constant redox potential MD (C(pH,E)MD), and for Replica Exchange MD along the redox potential dimension (E-REMD) on the AMBER software package. Validation results are presented for a small system that contains a single heme group: N-acetylmicroperoxidase-8 (NAcMP8) axially connected to a histidine peptide. The methods implemented allow one to make standard redox potential (E^o) predictions with the same easiness and accuracy as pK_a predictions using the constant pH molecular dynamics and pH-REMD methods currently available on AMBER. In our simulations, we can correctly describe, in agreement also with theoretical predictions, the following behaviors: when a redox-active group is reduced, the pK_a of a near pH-active group increases because it becomes easier for a proton to be attached; equivalently, when a pH-active group is protonated, the standard redox potential (E^o) of an adjacent redox-active group rises. Furthermore, our results also show that E-REMD is able to achieve faster statistical convergence than CEMD or C(pH,E)MD. Moreover, computational benchmarks using our methodologies show high-performance of GPU (Graphics Processing Unit) accelerated calculations in comparison to conventional CPU (Central Processing Unit) calculations.

The potential outcome of flavivirus and alphavirus co-infections is worrisome due to the development of severe diseases. Hundreds of millions of people worldwide live under the risk of infections caused by viruses like chikungunya virus (CHIKV, genusAlphavirus), dengue virus (DENV, genusFlavivirus), and zika virus (ZIKV, genusFlavivirus). So far, neither any drug exists against the infection by a single virus, nor against co-infection. The results described in our study demonstrate the inhibitory potential of two flavonoids derived from citrus plants: Hesperetin (HST) against NS2B/NS3^proof ZIKV and nsP2^proof CHIKV and, Hesperidin (HSD) against nsP2^proof CHIKV. The flavonoids are noncompetitive inhibitors and the determined IC₅₀values are in low µM range for HST against ZIKV NS2B/NS3^pro(12.6 ± 1.3 µM) and against CHIKV nsP2^pro(2.5 ± 0.4 µM). The IC₅₀for HSD against CHIKV nsP2^prowas 7.1 ± 1.1 µM. The calculated ligand efficiencies for HST were > 0.3, which reflect its potential to be used as a lead compound. Docking and molecular dynamics simulations display the effect of HST and HSD on the protease 3D models of CHIKV and ZIKV. Conformational changes after ligand binding and their effect on the substrate-binding pocket of the proteases were investigated. Additionally, MTT assays demonstrated a very low cytotoxicity of both the molecules. Based on our results, we assume that HST comprise a chemical structure that serves as a starting point molecule to develop a potent inhibitor to combat CHIKV and ZIKV co-infections by inhibiting the virus proteases.

Since the first report of a new pneumonia disease in December 2019 (Wuhan, China) the WHO reported more than 148 million confirmed cases and 3.1 million losses globally up to now. The causative agent of COVID-19 (SARS-CoV-2) has spread worldwide, resulting in a pandemic of unprecedented magnitude. To date, several clinically safe and efficient vaccines (e.g., Pfizer-BioNTech, Moderna, Johnson & Johnson, and AstraZeneca COVID-19 vaccines) as well as drugs for emergency use have been approved. However, increasing numbers of SARS-Cov-2 variants make it imminent to identify an alternative way to treat SARS-CoV-2 infections. A well-known strategy to identify molecules with inhibitory potential against SARS-CoV-2 proteins is repurposing clinically developed drugs, e.g., antiparasitic drugs. The results described in this study demonstrated the inhibitory potential of quinacrine and suramin against SARS-CoV-2 main protease (3CL^pro). Quinacrine and suramin molecules presented a competitive and noncompetitive inhibition mode, respectively, with IC₅₀ values in the low micromolar range. Surface plasmon resonance (SPR) experiments demonstrated that quinacrine and suramin alone possessed a moderate or weak affinity with SARS-CoV-2 3CL^pro but suramin binding increased quinacrine interaction by around a factor of eight. Using docking and molecular dynamics simulations, we identified a possible binding mode and the amino acids involved in these interactions. Our results suggested that suramin, in combination with quinacrine, showed promising synergistic efficacy to inhibit SARS-CoV-2 3CL^pro. We suppose that the identification of effective, synergistic drug combinations could lead to the design of better treatments for the COVID-19 disease and repurposable drug candidates offer fast therapeutic breakthroughs, mainly in a pandemic moment.

A simple method for simultaneous determination of gatifloxacin and prednisolone acetate in ophthalmic formulation was developed and validated using UV spectrophotometry. Gatifloxacin and prednisolone acetate were quantified using the first-order derivative of the UV spectra. The proposed method was validated according to the guidelines of the International Conference on Harmonization and the Association of Official Analytical Chemists International. The measurements were made in acetonitrile/water (70:30 v/v) at 348nm for gatifloxacin and at 263nm for prednisolone acetate. The calibration curves were linear in the concentration range of 3–21μgmL−1 for gatifloxacin and 6–42μgmL−1 for prednisolone acetate with Sandell’s sensitivities of 0.349μgcm−2 and 0.402μgcm−2, respectively. The mean recovery and the limit of quantification for gatifloxacin were 99.76±0.41% and 1.11μgmL−1 and for prednisolone acetate were 99.52±0.87% and 0.55μgmL−1, respectively. The method was precise, with a relative standard deviation of less than 2.50% for both drugs. For robustness, the factors analyzed did not significantly affect the quantification of gatifloxacin and prednisolone acetate. The results of the validated method did not differ significantly from high-performance liquid chromatography (HPLC), which was previously developed and validated for the same drugs. In this form, the method was suitable for routine analysis of gatifloxacin and prednisolone acetate in their combined dosage form in ophthalmic formulations

The objective of this research was to develop and validate an alternative analytical method for quantitative determination of levofloxacin in tablets and injection preparations. The calibration curves were linear over a concentration range from 3.0 to 8.0 μg mL-1. The relative standard deviation was below 1.0% for both formulations and average recovery was 101.42 ± 0.45% and 100.34 ± 0.85% for tablets and injection formulations, respectively. The limit of detection and limit of quantitation were 0.08 and 0.25 μg mL-1, respectively. It was concluded that the developed method is suitable for the quality control of levofloxacin in pharmaceuticals formulations.Fundação de Apoio ao Desenvolvimento de Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul (FAPEMS)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES