Five-Stage Approach for a Systematic Screening and Development of Etravirine Amorphous Solid Dispersions by Hot-Melt Extrusion.

The aim of this study was to develop a fast, effective, and material sparing screening method to design amorphous solid dispersions (ASDs) of etravirine to drive more effectively the development process, leading to improved bioavailability (BA) and stability. A systematic step-by-step approach was followed by combining theoretical calculations with high-throughput screening (HTS) and software-assisted multivariate statistical analysis. The thermodynamic miscibility and interaction of the drug in several polymers were predicted using Hansen solubility parameters (δ). The selected polymers were evaluated by HTS, using solvent evaporation. Binary compositions were evaluated by their solubilization capacity and physical stability over 2 months. JMP 14.0 was used for multivariate statistical analysis using principal components analysis. Extrusion was performed in Thermo Scientific HAAKE MiniLab II, and extrudates were characterized by assay, related substances, dissolution, and physical state (polarized light microscopy (PLM), Raman spectroscopy, and X-ray powder diffraction (XRPD)). A short stability study was performed where milled extrudates were exposed to 25 °C/60%RH and 40 °C/75%RH for 3 months. Through thermodynamic predictions, five main polymers were selected. The HTS enabled the evaluation of 42 formulations for solubilization capacity and physical stability. The three most promising compositions were selected for hot-melt extrusion (HME) tests. In general, a good correlation was found among the results of theoretical predictions, HTS, and HME. Poly(vinylpyrrolidone) (PVP)-based formulations were shown to be easily extrudable, with low degradation and complete amorphicity, whereas in Soluplus, the drug was not miscible, leading to a high crystalline content. The drug release rate was improved more than two times with PVP, and the manufactured ASD was demonstrated to be stable physically and chemically. A fast and effective screening technique to develop stable ASDs for a poorly soluble drug was successfully developed as applied to etravirine. The given method is easy to use, requires a low amount of drug, and is fairly accurate in predicting the amorphization of the drug when formulated. The success of HME formulation development of etravirine was undoubtedly enhanced with this high-throughput tool, which led to the identification of extrudates with improved biopharmaceutical properties. The structural characterization performed by PLM, XRPD, and Raman spectroscopy demonstrated that the HME prototype was essentially amorphous. The unexpected stability at 40 °C/75%RH was correlated with the presence of molecular interaction characterized by Raman spectroscopy.

Raman spectroscopy reveals distinct differences between two closely related bacterial strains, Mycobacterium indicus pranii and Mycobacterium intracellulare.

A common technique used to differentiate bacterial species and to determine evolutionary relationships is sequencing their 16S ribosomal RNA genes. However, this method fails when organisms exhibit high similarity in these sequences. Two such strains that have identical 16S rRNA sequences are Mycobacterium indicus pranii (MIP) and Mycobacterium intracellulare. MIP is of significance as it is used as an adjuvant for protection against tuberculosis and leprosy; in addition, it shows potent anti-cancer activity. On the other hand, M. intracellulare is an opportunistic pathogen and causes severe respiratory infections in AIDS patients. It is important to differentiate these two bacterial species as they co-exist in immuno-compromised individuals. To unambiguously distinguish these two closely related bacterial strains, we employed Raman and resonance Raman spectroscopy in conjunction with multivariate statistical tools. Phenotypic profiling for these bacterial species was performed in a kinetic manner. Differences were observed in the mycolic acid profile and carotenoid pigments to show that MIP is biochemically distinct from M. intracellulare. Resonance Raman studies confirmed that carotenoids were produced by both MIP as well as M. intracellulare, though the latter produced higher amounts. Overall, this study demonstrates the potential of Raman spectroscopy in differentiating two closely related mycobacterial strains. Graphical abstract.

Molecular structure and vibrational spectroscopic studies of prothionamide by density functional theory.

Prothionamide (PTH) is the secondary drug used against Mycobacterium tuberculosis bacteria and leprosy. The aim of this work was to investigate the potential energy surface map, anharmonic and harmonic vibrational spectra, NBO analysis and ELF (Electron Localization Function) of the title compound using DFT approach with the B3LYP (Becke, three-parameter, Lee-Yang-Parr) exchange-correlation functional with the 6-31G++(d,p) and the Z3POLX basis sets were employed. In the experimental part of this study, FT-Mid IR, FT-Far IR and FT-Raman spectra of the molecule were recorded in the regions 4000-450cm(-1), 700-30cm(-1) and 4000-100cm(-1) respectively in the solid phase. The comparison between calculated and experimental vibrational spectra (infrared and Raman spectra) and assignments of fundamental vibrational modes were characterized by total energy distribution (TED). Theoretical spectra were seen to be in good agreement with those of the experimental ones.

Theoretical and experimental electrostatic potential around the m-nitrophenol molecule.

This work concerns a comparison of experimental and theoretical results of the electron charge density distribution and the electrostatic potential around the m-nitrophenol molecule (m-NPH) known for its interesting physical characteristics. The molecular experimental results have been obtained from a high-resolution X-ray diffraction study. Theoretical investigations were performed using the Density Functional Theory at B3LYP level of theory at 6-31G* in the Gaussian program. The multipolar model of Hansen and Coppens was used for the experimental electron charge density distribution around the molecule, while we used the DFT methods for the theoretical calculations. The electron charge density obtained in both methods allowed us to find out different molecular properties such us the electrostatic potential and the dipole moment, which were finally subject to a comparison leading to a good match obtained between both methods. The intramolecular charge transfer has also been confirmed by an HOMO-LUMO analysis.

Synthesis, Raman, FT-IR, NMR spectroscopic data and antimicrobial activity of mixed aza-oxo-thia macrocyclic compounds.

Mixed aza-oxo-thia macrocyclic ligands 1,3,5,11,13,15-hexaaza-6,10,16,20-tetraoxo-8,18-dithia-2,3,4:12,13,14-dipyridine cyclocosane (L(1)); 1,3,5,12,14,16-hexeaza-6,11,17,22-tetraoxo-8,9,19,20-tetrathia-2,3,4:13,14,15-dipyridine cyclodocosane (L(2)); 1,3,5,13,15,17-hexaaza-6,12,18,24-tetraoxo-9,21-dithia-2,3,4:14,15,16-dipyridine cyclotetracosane (L(3)) and 1,3,5,14,16,18-hexaaza-6,13,19,26-tetraoxo-9,10,22,23-tetrathia-2,3,4:15,16,17-dipyridine cyclohexacosane (L(4)) were synthesised. The structural features of the ligands have been studied by elemental analyses, Raman, IR, (1)H and (13)C NMR spectroscopy. The antimicrobial activities of the ligands were evaluated using disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against nine bacteria. The obtained results from disk diffusion method were assessed in side-by-side comparison with those of penicillin G, ampicillin, cefotaxime, vancomycin, ofloxacin, and tetracycline well known antibacterial agents. The results from dilution procedure were compared with gentamycin as antibacterial and nystatin as antifungal. The antifungal activities are reported on five yeast cultures namely Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii, and Hanseniaspora guilliermondii, and the results are referenced with nystatin, Ketoconazole, and clotrimazole, commercial antifungal agents. In most cases, the compounds show broad-spectrum (Gram(+) and Gram(-) bacteria) activities that were more active or equipotent to the antibiotic and antifungal agents in the comparison tests.

Synthesis, characterization and antimicrobial activity of Fe(II), Zn(II), Cd(II) and Hg(II) complexes with 2,6-bis(benzimidazol-2-yl) pyridine ligand.

2,6-Bis(benzimidazol-2-yl)pyridine (L) ligand and complexes [M(L)Cl(2)] and [Fe(L)(2)](ClO(4))(2) (M=Zn, Cd, Hg) have been synthesized. The geometries of the [M(L)Cl(2)] complexes were derived from theoretical calculation in DGauss/DFT level (DZVP basis set) on CACHE. The central M(II) ion is penta-coordinated and surrounded by N(3)Cl(2) environment, adopting a distorted trigonal bipyramidal geometry. The ligand is tridentate, via three nitrogen atoms to metal centre and two chloride ions lie on each side of the distorted benzimidazole ring. In the [Fe(L)(2)](ClO(4))(2) complex, the central Fe(II) ion is surrounded by two (3N) units, adopting a octahedral geometry. The elemental analysis, molecular conductivity, FT-Raman, FT-IR (mid-, far-IR), (1)H, and (13)C NMR were reported. The antimicrobial activities of the free ligand, its hydrochloride salt, and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide (DMSO) as well as the minimal inhibitory concentration (MIC) dilution method, against 10 bacteria and the results compared with that for gentamycin. Antifungal activities were reported for Candida albicans, Kluyveromyces fragilis, Rhodotorula rubra, Debaryomyces hansenii, Hanseniaspora guilliermondii, and the results were referenced against nystatin, ketaconazole, and clotrimazole antifungal agents. In most cases, the compounds tested showed broad-spectrum (Gram positive and Gram negative bacteria) activities that were either more effective than or as potent as the references. The binding of two most biologically effective compounds of zinc and mercury to calf thymus DNA has also been investigated by absorption spectra.