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Sarah Straßmann Tillman Brehmer Maike Passon Andreas Schieber 《Molecules (Basel, Switzerland)》2021,26(5)
The approach presented in this study is the first for the hemisynthesis of methylated anthocyanins. It was possible to obtain cyanidin-3-O-glucoside derivatives with different degrees of methylation. Cautious identification of 4′-, 5-, and 7-OH monomethylated derivatives was also accomplished. The methylation agent used was the “green chemical” dimethyl carbonate (DMC), which is characterized by low human and ecological toxicity. The influence of the temperature, reaction time, and amount of the required diazabicyclo[5.4.0]undec-7-en (DBU) catalyst on the formation of the products was examined. Compared to conventional synthesis methods for methylated flavonoids using DMC and DBU, the conditions identified in this study result in a reduction of reaction time, and an important side reaction, so-called carboxymethylation, was minimized by using higher amounts of catalyst. 相似文献
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Tina Friedenauer Kim Buck Maike Eberwein Anna-Lena Bünte Christoph Rehbock Stephan Barcikowski 《Particle & Particle Systems Characterization》2023,40(12):2300034
One challenge in the development of new drug formulations is overcoming their low solubility in relevant aqueous media. Reducing the particle size of drug powders to a few hundred nanometers is a well-known method that leads to an increase in solubility due to an elevated total surface area. However, state-of-the-art comminution techniques like cryo-milling suffer from degradation and contamination of the drugs, particularly when sub-micrometer diameters are aspired that require long processing times. In this work, picosecond-pulsed laser fragmentation in liquids (LFL) of dispersed drug particles in a liquid-jet passage reactor is used as a wear-free comminution technique using the hydrophobic oral model drugs naproxen, prednisolone, ketoconazole, and megestrol acetate. Particle size and morphology of the drug particles are characterized using scanning electron microscopy (SEM) and changes in particle size distributions upon irradiation are quantified using an analytical centrifuge. The findings highlight the superior fragmentation efficiency of the liquid-jet passage reactor setup, with a 100 times higher fraction of submicrometer particles (SMP) of the drugs compared to the batch control, which enhances solubility and goes along with minimal chemical degradation (<1%), determined by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), high-performance liquid chromatography (HPLC), and X-ray diffraction (XRD). Moreover, the underlying predominantly photo-mechanically induced laser fragmentation mechanisms of organic microparticles (MP) are discussed. 相似文献
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Thiele J Windbergs M Abate AR Trebbin M Shum HC Förster S Weitz DA 《Lab on a chip》2011,11(14):2362-2368
Early development drug formulation is exacerbated by increasingly poor bioavailability of potential candidates. Prevention of attrition due to formulation problems necessitates physicochemical analysis and formulation studies at a very early stage during development, where the availability of a new substance is limited to small quantities, thus impeding extensive experiments. Miniaturization of common formulation processes is a strategy to overcome those limitations. We present a versatile technique for fabricating drug nanoformulations using a microfluidic spray dryer. Nanoparticles are formed by evaporative precipitation of the drug-loaded spray in air at room temperature. Using danazol as a model drug, amorphous nanoparticles of 20-60 nm in diameter are prepared with a narrow size distribution. We design the device with a geometry that allows the injection of two separate solvent streams, thus enabling co-spray drying of two substances for the production of drug co-precipitates with tailor-made composition for optimization of therapeutic efficiency. 相似文献
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We prove that the Shapley value of every two-sided exact assignment game lies in the core of the game. 相似文献
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Tina Brueckner Anita Eberl Sonja Heumann Maike Rabe Georg M. Guebitz 《Journal of polymer science. Part A, Polymer chemistry》2008,46(19):6435-6443
Alkaline and enzymatic hydrolyzes of poly(ethylene terephthalate) fabrics (PET) were mechanistically compared based on released degradation products (HPLC‐UV‐RI) and changes in surface properties [hydrophilicity, cationic dyeing, X‐ray photoelectron spectroscopy (XPS)]. Enzymatic hydrolysis led to an increase in the amount of hydroxyl and carboxyl groups on the surface resulting in an enhanced water absorption and dyeability. Enzymes partially adsorbed to PET fabrics during hydrolysis were completely removed by subsequent extraction according to XPS analysis. In contrast to the enzyme treatment, alkaline hydrolysis did not lead to an increase of hydroxyl and acid groups according to XPS while both treatments caused a substantial increase in hydrophilicity and were more effective on amorphous fibers. Alkaline hydrolysis led to a greater increase in the K/S value after cationic dyeing due to enlarged surface area. Consequently, ESEM‐images demonstrated that alkaline treatment drastically affected the surface morphology of the polymer resulting in crater‐like structures of the fibers, whereas after enzymatic treatment the morphology of the fibers remained unchanged. To reach similar benefits in hydrophilicity, drastically higher amounts of degradation products were released during alkaline hydrolysis as also indicated by >6% weight loss compared to <1% after enzyme treatment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6435–6443, 2008 相似文献
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[Ba2(H2O)9][GeSe4] is suitable for the formation of novel M/14/16 anions [Mn6Ge4Se17]6- --discrete or linked in an as yet unprecedented porous network--with antiferromagnetically coupled Mn(II) centers and relatively small electronic excitation energies. 相似文献
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A suitable measure for the similarity of shapes represented by parameterized curves or surfaces is the Fréchet distance. Whereas
efficient algorithms are known for computing the Fréchet distance of polygonal curves, the same problem for triangulated surfaces
is NP-hard. Furthermore, it remained open whether it is computable at all.
Using a discrete approximation, we show that it is upper semi-computable, i.e., there is a non-halting Turing machine which produces a decreasing sequence of rationals converging to the Fréchet
distance. It follows that the decision problem, whether the Fréchet distance of two given surfaces lies below a specified
value, is recursively enumerable. 相似文献
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