Determination of polysorbate 80 in parenteral formulations by high-performance liquid chromatography and evaporative light scattering detection

Drugs that are not very soluble in aqueous formulations are solubilized with surfactants such as polysorbate 80. In order to evaluate the stability of excipient such as polysorbate 80 in drug formulation, a rapid chromatographic methodology is desired; however, polysorbate 80 does not have a strong chromophore for monitoring by absorption spectrometry. A simple and fast method for the analysis of polysorbate 80 in pharmaceutical formulations was developed using high-performance liquid chromatography with evaporative light scattering detection (ELSD). Separation of polysorbate 80 as a single peak was achieved on a C18 column using a methanol/water gradient mobile phase and ELS detection. The method is specific for polysorbate 80 in the formulation as there were no interferences from the drug or other excipients. Precision, recovery, linearity and limit of quantitation/detection experiments gave acceptable results during the evaluation of the method.     

Study of the effects of ion pairing and activity coefficients on the separation in standard potentials for two-step reduction of dinitroaromatics

The electrochemical reduction of 9,10-dinitroanthracene, 1, and 3,6-dinitrodurene, 2, occurs with potential inversion. That is, the standard potential for formation of the anion radical is shifted in the negative direction from the standard potential for the anion radical/dianion couple. This behavior has been attributed to significant structural changes accompanying the reduction steps. In this work, an assessment was made of the magnitude of the effects of activity coefficients and ion pairing, two effects which contribute to potential inversion. 1,4-Dinitrobenzene, 3, and 2,5-dimethyl-1,4-dinitrobenzene, 4, were studied in acetonitrile and N,N-dimethylformamide with R(4)N(+) salts as electrolytes (R = CH(3)-, CH(3)CH(2)-, CH(3)(CH(2))(3)-, and CH(3)(CH(2))(7)-) at concentrations from 0.010 to 0.100 M. Significant ion pairing between the dianion, A(2-), and R(4)N(+) was found for (CH(3))(4)N(+) with both 3 and 4 while the effects of the other electrolytes were smaller. The data were successfully interpreted without recourse to other ion pairs, e.g., ion pairing between the anion radical and the electrolyte cation. Ion pair formation constants are reported along with the infinite-dilution values of the difference in the two standard potentials. The effects of activity coefficients and ion pairing at 0.10 M electrolyte do not exceed 100 mV for (CH(3)N(+)) and are only 20 to 60 mV for (CH(3))(4)N(+), a cation commonly used in studies of potential inversion. It is concluded that structural changes accompanying the reduction, rather than activity and ion pairing effects, are the dominant factors underlying potential inversion.     

Liquid chromatographic determination of multiple sulfonamides, nitrofurans, and chloramphenicol residues in pasteurized milk

A rapid and selective liquid chromatographic method was developed to detect 6 sulfonamides, 3 nitrofurans, and chloramphenicol residues in pasteurized milk. The 10 drugs were extracted with chloroform-acetone and the organic phase was evaporated; the residues were dissolved in an aqueous sodium acetate buffer solution 0.02M (pH = 4.8), and the fat was removed by washing with hexane. The aqueous layer was collected, filtered, and injected. The 6 sulfonamides and chloramphenicol were detected at 275 nm ultraviolet (UV) using a gradient system starting with sodium acetate buffer solution-acetonitrile (95 + 5) and finishing with sodium acetate buffer solution-acetonitrile (80 + 20). Nitrofurans were detected at 375 nm (UV) isocratically with sodium acetate buffer solution-acetonitrile (80 + 20). For 50 ppb fortified milk, the average recoveries were (sulfathiazole) 65.52%; (sulfamerazine) 75.36%; (sulfamethazine) 93.94%; (sulfachlorpyridazine) 75.94%; (sulfamethoxazole) 85.18%; (sulfamonomethoxine) 83.45%; (chloramphenicol) 104.17%; (nitrofurazone) 91.81%; (furazolidone) 100.76%; and (furaltadone) 72.38%. Method detection limits ranged from 4 ppb (nitrofurazone) to 16 ppb (sulfamethazine). Some matrix interferences (3-7 ppb) were observed only with sulfonamides.     

Studies of the electrochemical reduction of some dinitroaromatics

The electrochemical reduction of a series of dinitroaromatics, along with one trinitro compound, has been investigated at a glassy carbon electrode in N,N-dimethylformamide. The separation between the two standard potentials for the reduction, E°₁ − E°₂, has been determined and discussed in terms of the structures of the compounds. cis-4,4′-Dinitrostilbene was shown to undergo redox-catalyzed isomerization to the trans isomer. This was demonstrated with partial controlled potential electrolysis followed by chromatographic analysis of the solution. It was also found that redox-catalyzed isomerization could adequately account for the voltammetric behavior. The anion radicals of 3,5-dinitropyridine and 1,3,5-trinitrobenzene undergo reversible dimerization reactions. The rate and equilibrium constants for the dimerization were determined by simulation of the voltammograms of these two compounds and also by simulation of the voltammograms obtained with solutions from the one-electron controlled potential reduction, that is, solutions of the dimer. The equilibrium constants for dimerization were also determined by electron paramagnetic resonance spectroscopy.     

New β-orcinol depsides from Hypotrachyna caraccensis,a lichen from the páramo ecosystem and their free radical scavenging activity

The new hypotrachynin A (1) and B (2) along with the known (+)-(9b-R)-usnic (3) and methylstictic acids (4) were isolated for the first time from Hypotrachyna caraccensis. Additionally, their potency and reactivity as DPPH? scavengers was determined by a kinetic study calculating their EC₅₀ and second-order rate constants (k₂). Considering 1–4 could be dermatological agents, their n-octanol-water partition coefficients and standard molar Gibbs free energies of transfer were calculated as estimation of their lipophilicity and skin penetration. Compounds 1, 3 and 4 were less potent than 2 (EC₅₀ = 3.3014; 1.7540; 2.6652 vs 0.7376) as DPPH? scavengers, in turn 4, was the most reactive with a comparable k₂ to the antioxidant BHT (k₂ = (232 ± 24) × 10^?2 vs (564 ± 12) × 10^?2 M^?1 s^?1, respectively). Since 2 and 4 had an optimal lipophilicity and permeability for skin penetration, they might be developed as topical ingredients to prevent oxidative damage.     

Rapid Determination of Phenolics,Flavonoids, and Antioxidant Properties of Physalis ixocarpa Brot. ex Hornem. and Physalis angulata L. by Infrared Spectroscopy and Partial Least Squares

Physalis ixocarpa Brot. ex Hornem. and Physalis angulata L. are two edible species of the family Solanaceae, which have an important variety of antioxidant compounds present in their roots, stems, leaves, calyces, and fruits. This work reports the development of multivariate models based on the use of partial least square (PLS) analysis and Fourier transform infrared (FTIR) spectroscopy for the quantitative determination of total phenolics, total flavonoids, free radical scavenging activity, total antioxidant capacity, and reducing power in the extracts of roots, stems, and leaves of both P. ixocarpa and P. angulata. Standard chromatographic and colorimetric techniques were used to determine the quantitative actual values (references) in the extracts, which served as input data to develop the multivariate PLS models. Optimized FTIR-PLS models were realized by cross-validation procedures, obtaining the determination coefficients for prediction between 0.792 and 0.905 for P. ixocarpa, and between 0.756 and 0.893 for P. angulata. In this form, FTIR spectroscopy with multivariate analysis could represent a versatile tool to evaluate quantitatively concentrations of bioactive compounds and antioxidant properties in the extracts of both species, requiring a very short time at low cost.     

Synthesis of polymer/Laponite nanocomposite latex particles via emulsion polymerization using silylated and cation-exchanged Laponite clay platelets

We report the synthesis and characterization of polymer/Laponite nanocomposite latex particles through emulsion polymerization using organically modified Laponite clay platelets as seeds. Two approaches were adopted for the organic modification of Laponite. The first one is based on the grafting of either γ-methacryloyloxy propyl dimethyl-methoxysilane (γ-MPDES) or γ-methacryloyloxy propyl triethoxysilane (γ-MPTES) on the clay edges. The other strategy consists in exchanging the clay interlayer sodium ions by either a free radical initiator, 2,2-azobis(2-methyl propionamidine)hydrochloride (AIBA) or a cationic vinyl monomer, 2-(methacryloyloxy)ethyl trimethyl ammonium chloride (MADQUAT). The grafting was characterized both qualitatively using FTIR and quantitatively using elemental analysis or UV analysis. The results show that the degree of functionalization depends on the nature of the organic modifier. Before performing the emulsion polymerization reaction, the functionalized clay platelets were successfully dispersed in water. Nanocomposite latexes were then synthesized using a mixture of styrene (Styr) and butyl acrylate (BA) and sodium dodecyl sulphate (SDS) as anionic surfactant. An important result of the present work is that clay redispersion in water is a key step of the overall process. The larger the size of the clay aggregates, the poorer the stability of the resulting latex suspension. The morphology and mechanism of formation of the nanocomposite particles are discussed.     

Conformational insights into furo- and thieno[2,3-b]indolines derived from coupling constants and molecular modeling

The extent to which conformational preferences of fused heterocyclic five-membered rings change with the nature of the heteroatom (O and S) was investigated in furo- (1, 2) and thieno[2,3-b]indolines (3, 4) by the combined use of 1H NMR spectroscopy and density functional theory (DFT) calculations. In contrast to the behavior observed for pyrroloindolines, the furo- and thienoindolines exist in solution in only one conformer, with structures in the 2E-2T3 (1,2) and 2T3-E (3,4) North/West region of the pseudorotational wheel, and with pseudorotation phase angles (P) of 315.8, 311.6, 337.2 and 331.6 degrees, respectively.     

Efficacy of DA-7218, a new oxazolidinone prodrug, in the treatment of experimental actinomycetoma produced by Nocardia brasiliensis

Two recently synthesized oxazolidinones: (R)-3-(4-(2-(2-methyltetrazol-5-yl)-pyridin-5-yl)-3-fluorophenyl)-5-hydroxymethyloxazolidin-2-one (DA-7157) and its corresponding pro-drug (R)-3-(4-(2-(2-methyltetrazol-5-yl)-pyridin-5-yl)-3-fluorophenyl)-2-oxo-5-oxazolidinyl) methyl disodium phosphate (DA-7218), have shown very good activity against several Gram positive bacteria, including Nocardia and Mycobacterium. In the present work we evaluated the therapeutic in vivo effects of DA-7218 on Nocardia brasiliensis. We first determined the plasma concentration of the prodrug in BALB/c mice using several doses and then tested its activity in an in vivo experimental actinomycetoma murine model. At the end of treatment, there was a statistically significant difference between the three drug receiving groups (25, 12.5 and 5 mg/kg) and the control group(saline solution) (p=0.001), proving that DA-7218 is effective for the treatment of experimental murine actinomycetoma. This compound could be a potential option for patients affected with mycetoma by Nocardia brasiliensis.     

Compatibilization of Poly(Lactic Acid) (PLA)/Plasticized Cellulose Acetate Extruded Blends through the Addition of Reactively Extruded Comb Copolymers

In the perspective of producing a rigid renewable and environmentally friendly rigid packaging material, two comb-like copolymers of cellulose acetate (AC) and oligo(lactic acid) OLA, feeding different percentages of oligo(lactic acid) segments, were prepared by chemical synthesis in solvent or reactive extrusion in the melt, using a diepoxide as the coupling agent and were used as compatibilizers for poly(lactic acid)/plasticized cellulose acetate PLA/pAC blends. The blends were extruded at 230 °C or 197 °C and a similar compatibilizing behavior was observed for the different compatibilizers. The compatibilizer C1 containing 80 wt% of AC and 14 wt% of OLA resulted effective in compatibilization and it was easily obtained by reactive extrusion. Considering these results, different PLAX/pAC(100-X) compounds containing C1 as the compatibilizer were prepared by extrusion at 197 °C and tested in terms of their tensile and impact properties. Reference materials were the uncompatibilized corresponding blend (PLAX/pAC(100-X)) and the blend of PLA, at the same wt%, with C1. Significant increase in Young’s modulus and tensile strength were observed in the compatibilized blends, in dependence of their morphologic features, suggesting the achievement of an improved interfacial adhesion thanks to the occurred compatibilization.