Thiogenistein-Antioxidant Chemistry, Antitumor Activity, and Structure Elucidation of New Oxidation Products.

Isoflavonoids such as genistein (GE) are well known antioxidants. The predictive biological activity of structurally new compounds such as thiogenistein (TGE)-a new analogue of GE-becomes an interesting way to design new drug candidates with promising properties. Two oxidation strategies were used to characterize TGE oxidation products: the first in solution and the second on the 2D surface of the Au electrode as a self-assembling TGE monolayer. The structure elucidation of products generated by different oxidation strategies was performed. The electrospray ionization mass spectrometry (ESI-MS) was used for identifying the product of electrochemical and hydrogen peroxide oxidation in the solution. Fourier transform infrared spectroscopy (FT-IR) with the ATR mode was used to identify a product after hydrogen peroxide treatment of TGE on the 2D surface. The density functional theory was used to support the experimental results for the estimation of antioxidant activity of TGE as well as for the molecular modeling of oxidation products. The biological studies were performed simultaneously to assess the suitability of TGE for antioxidant and antitumor properties. It was found that TGE was characterized by a high cytotoxic activity toward human breast cancer cells. The research was also carried out on mice macrophages, disclosing that TGE neutralized the production of the LPS-induced reactive oxygen species (ROS) and exhibits ABTS (2,2'-azino-bis-3-(ethylbenzothiazoline-6-sulphonic acid) radical scavenging ability. In the presented study, we identified the main oxidation products of TGE generated under different environmental conditions. The electroactive centers of TGE were identified and its oxidation mechanisms were proposed. TGE redox properties can be related to its various pharmacological activities. Our new thiolated analogue of genistein neutralizes the LPS-induced ROS production better than GE. Additionally, TGE shows a high cytotoxic activity against human breast cancer cells. The viability of MCF-7 (estrogen-positive cells) drops two times after a 72-h incubation with 12.5 µM TGE (viability 53.86%) compared to genistein (viability 94.46%).

Development of Composite, Reinforced, Highly Drug-Loaded Pharmaceutical Printlets Manufactured by Selective Laser Sintering-In Search of Relevant Excipients for Pharmaceutical 3D Printing.

3D printing by selective laser sintering (SLS) of high-dose drug delivery systems using pure brittle crystalline active pharmaceutical ingredients (API) is possible but impractical. Currently used pharmaceutical grade excipients, including polymers, are primarily designed for powder compression, ensuring good mechanical properties. Using these excipients for SLS usually leads to poor mechanical properties of printed tablets (printlets). Composite printlets consisting of sintered carbon-stained polyamide (PA12) and metronidazole (Met) were manufactured by SLS to overcome the issue. The printlets were characterized using DSC and IR spectroscopy together with an assessment of mechanical properties. Functional properties of the printlets, i.e., drug release in USP3 and USP4 apparatus together with flotation assessment, were evaluated. The printlets contained 80 to 90% of Met (therapeutic dose ca. 600 mg), had hardness above 40 N (comparable with compressed tablets) and were of good quality with internal porous structure, which assured flotation. The thermal stability of the composite material and the identity of its constituents were confirmed. Elastic PA12 mesh maintained the shape and structure of the printlets during drug dissolution and flotation. Laser speed and the addition of an osmotic agent in low content influenced drug release virtually not changing composition of the printlet; time to release 80% of Met varied from 0.5 to 5 h. Composite printlets consisting of elastic insoluble PA12 mesh filled with high content of crystalline Met were manufactured by 3D SLS printing. Dissolution modification by the addition of an osmotic agent was demonstrated. The study shows the need to define the requirements for excipients dedicated to 3D printing and to search for appropriate materials for this purpose.

Anti-Cancer and Electrochemical Properties of Thiogenistein-New Biologically Active Compound.

Pharmacological and nutraceutical effects of isoflavones, which include genistein (GE), are attributed to their antioxidant activity protecting cells against carcinogenesis. The knowledge of the oxidation mechanisms of an active substance is crucial to determine its pharmacological properties. The aim of the present work was to explain complex oxidation processes that have been simulated during voltammetric experiments for our new thiolated genistein analog (TGE) that formed the self-assembled monolayer (SAM) on the gold electrode. The thiol linker assured a strong interaction of sulfur nucleophiles with the gold surface. The research comprised of the study of TGE oxidative properties, IR-ATR, and MALDI-TOF measurements of SAM before and after electrochemical oxidation. TGE has been shown to be electrochemically active. It undergoes one irreversible oxidation reaction and one quasi-reversible oxidation reaction in PBS buffer at pH 7.4. The oxidation of TGE results in electroactive products composed likely from TGE conjugates (e.g., trimers) as part of polymer. The electroactive centers of TGE and its oxidation mechanism were discussed using IR supported by quantum chemical and molecular mechanics calculations. Preliminary in-vitro studies indicate that TGE exhibits higher cytotoxic activity towards DU145 human prostate cancer cells and is safer for normal prostate epithelial cells (PNT2) than genistein itself.

The ligand exchange of citrates to thioabiraterone on gold nanoparticles for prostate cancer therapy.

Cancer is one of the leading causes of morbidity and mortality worldwide and nanotechnology has a significant potential to enhance the therapeutic and diagnostic performance of anti-cancer agents. Our work offers a simple and feasible strategy for thiocompound nanomedicines to be used in cancer therapy. Novel gold nanoparticles conjugated with thioabiraterone (AuNP-S-AB) were synthesized and significant new analytical methodologies were developed for their characterization by UV-Vis, TEM, IR, NMR and TGA. Our synthetic approach was based on the ligand exchange of citrates to thioabiraterone on gold nanoparticles. The average particle size of AuNP-S-AB was 14.5 nm with a spherical shape. The identity of thioabiraterone on the gold nanoparticles was proved by NMR and IR spectroscopy. The coverage of the gold nanoparticles with 40.9% (m/m) thioabiraterone was calculated from a TGA analysis. Molecular interactions between the thiol group of thioabiraterone and gold nanoparticles were evaluated through a combined experimental and theoretical study using the density functional theory (DFT). Additionally, an experiment conducted on hepatocytes or human prostate epithelial cells proved that newly synthesized thiol forms of abiraterone, as well as AuNP-S-AB, are more biocompatible than abiraterone. Our proposed idea of delivering abiraterone with our newly designed AuNP-S-AB may constitute a promising and novel prospect in cancer therapy.

Design and Molecular Modeling of Abiraterone-Functionalized Gold Nanoparticles.

The aim of our work was the synthesis and physicochemical characterization of a unique conjugate consisting of gold nanoparticles (AuNPs) and a pharmacologically active anticancer substance abiraterone (AB). The direct coupling of AB with gold constitutes an essential feature of the unique AuNPs⁻AB conjugate that creates a promising platform for applications in nanomedicine. In this work, we present a multidisciplinary, basic study of the obtained AuNPs⁻AB conjugate. Theoretical modeling based on the density functional theory (DFT) predicted that the Aun clusters would interact with abiraterone preferably at the N-side. A sharp, intense band at 1028 cm-1 was observed in the Raman spectra of the nanoparticles. The shift of this band in comparison to AB itself agrees well with the theoretical model. AB in the nanoparticles was identified by means of electrochemistry and NMR spectroscopy. The sizes of the Au crystallites measured by XRPD were about 9 and 17 nm for the nanoparticles obtained in pH 7.4 and 3.6, respectively. The size of the particles as measured by TEM was 24 and 30 nm for the nanoparticles obtained in pH 7.4 and pH 3.6, respectively. The DLS measurements revealed stable, negatively charged nanoparticles.

Process-related impurities of eplerenone: determination and characterisation by HPLC methods and Raman spectroscopy.

Two novel high-performance liquid chromatography methods for the determination of process-related impurities of eplerenone drug substance and the designated starting material were developed and validated. Process impurities, including stereoisomers of eplerenone and the intermediate, were controlled using a Kromasil C18 column (250 mm x 4.6 mm; particle size 5 µm), under gradient conditions. Simple mobile phases: water and acetonitrile, as well as a PDA detector set at 240 nm were used. In order to control the stereochemical purity of the starting material (SM) in the eplerenone synthesis the polysaccharide-based Kromasil 5-AmyCoat chiral stationary phase was applied. To confirm the identity of the process-related impurities (nine compounds) Raman Spectroscopy (RS), as a fast and convenient method, was applied. Differences in the wavenumbers of CC and CO stretching vibrations were the most distinctive features for the identification by means of RS. The bands assignment was supported by quantum mechanical computations. For one pair of the epimers containing the hydroxyl group the O-H…O bond geometry was correlated with the wavenumbers of stretching vibrations of this group. Wherever possible, experimental results were compared with literature data.

Pemetrexed conjugated with gold nanoparticles - Synthesis, characterization and a study of noncovalent interactions.

Gold nanoparticles (AuNPs) have been widely used as nanocarriers in drug delivery application. However, the binding mechanism between AuNPs and drug bases still remains a puzzle. Our study included: (i) optimization of three synthesis of the AuNPs-pemetrexed (PE) nanocomposites formation which was monitored by UV-Vis spectroscopy, (ii) identification of PE in gold nanocomposites and mechanism of PE interaction with gold nanoparticles by electrochemistry, NMR and Raman measurements, (iii) characterization of the three nanocomposites by TEM, DSL, ESL, zeta potential, XRPD and TGA analysis. The obtained nanocomposites are homogeneously shaped and have a maximum diameter of around 14nm and 88nm, as measured by the TEM and DSL techniques, respectively. The zeta potential of the nanocomposites is -43mV and suggests a high stability of the nanoparticles and lower toxicity for the normal cells. Quantum chemical calculations were also performed on model systems to estimate the strength of the AuNPs-PE interaction. Taking into account the experimental and theoretical data a mechanism of the nanocomposites' formation has been proposed in which PE interacts with the gold surface by the COOH/COO- group.

Synthesis and characterization of genistein conjugated with gold nanoparticles and the study of their cytotoxic properties.

Gold nanoparticles conjugated with drug substances are used in diagnostics and therapies. Apart from the combinations involving gold nanoparticles conjugated with drug substances through linkers, a direct bonding is also known. In our paper the example of such a direct bonding between gold nanoparticles and genistein (AuNPs-GE) is presented. This conjugate was obtained in a one-pot synthesis and the formation of AuNPs-GE was monitored in terms of color change and UV-Vis spectroscopy. It has been shown that genistein reduces Au3+ ions to spherical Au0 nanocrystallites and acts as a stabilizing agent. The efficiency of the purification of the conjugate from free genistein was controlled by the capillary electrophoresis. Gold nanoparticles are homogeneously shaped and have a narrow range of size from 14 to 33nm and the size of the nanoparticles modified with genistein is around 64.64±0.41nm, as measured by the TEM and DSL techniques, respectively. The zeta potential of the gold nanoparticles modified with genistein is -19.32±0.82mV and suggests a high stability of the nanoparticles and lower toxicity for the normal cells. The identity of genistein on the gold nanoparticles was proved by the electrochemistry, NMR and Raman spectroscopy. The mechanism of the conjugate forming has been proposed. The coverage of gold nanoparticles with genistein 5.09% (m/m) has been calculated from the TGA analysis. Moreover, it has been proved that the obtained conjugate is characterized by a high cytotoxic activity towards cancer cells, as observed in the cell line test.

Structural and Physicochemical Studies of Olopatadine Hydrochloride Conformational Polymorphs.

Crystal and molecular structures of 2 conformational polymorphs (forms I and II) of olopatadine hydrochloride, an antiallergic agent, are presented. Both crystal modifications crystallize in the monoclinic crystal system with 1 olopatadine hydrochloride molecule in the Z configuration in the asymmetric unit. Molecules are arranged into the centrosymmetric association through the interactions of the intermolecular strong and weak hydrogen bonds of N-H…Cl, O-H…Cl and C-H…Cl, C-H…O types. Conformational change between polymorphs is proved by calculations of a maximum torsion angle deviation (max[Δθ]) and a root-mean-square deviation between the atomic positions (rmsd[r]). The physicochemical characterization of polymorphs is performed by X-ray powder diffraction, infrared and Raman spectroscopy, differential scanning calorimetry. The comparison of the melting points and heats of fusions shows that the forms are monotropically related.

Studies of phase transitions in the aripiprazole solid dosage form.

Studies of the phase transitions in an active substance contained in a solid dosage form are very complicated but essential, especially if an active substance is classified as a BCS Class IV drug. The purpose of this work was the development of sensitive methods for the detection of the phase transitions in the aripiprazole tablets containing initially its form III. Aripiprazole exhibits polymorphism and pseudopolymorphism. Powder diffraction, Raman spectroscopy and differential scanning calorimetry methods were developed for the detection of the polymorphic transition between forms III and I as well as the phase transition of form III into aripiprazole monohydrate in tablets. The study involved the initial 10 mg and 30 mg tablets, as well as those stored in Al/Al blisters, a triplex blister pack and HDPE bottles (with and without desiccant) under accelerated and long term conditions. The polymorphic transition was not observed in the initial and stored tablets but it was visible on the DSC curve of the Abilify(®) 10 mg reference tablets. The formation of the monohydrate was observed in the diffractograms and Raman spectra in the tablets stored under accelerated conditions. The monohydrate phase was not detected in the tablets stored in the Al/Al blisters under long term conditions. The results showed that the Al/Al blisters can be recommended as the packaging of the aripiprazole tablets containing form III.

New Polymorphic Forms of Pemetrexed Diacid and Their Use for the Preparation of Pharmaceutically Pure Amorphous and Hemipentahydrate Forms of Pemetrexed Disodium.

The preparation of stable amorphous pemetrexed disodium of pharmaceutical purity as well as the process optimization for the preparation of the hemipentahydrate form of pemetrexed disodium are described. Analytical methods for the polymorphic and chemical purity studies of pemetrexed disodium and pemetrexed diacid forms were developed. The physicochemical properties of the amorphous and hydrate forms of pemetrexed disodium, as well as new forms of pemetrexed diacid (a key synthetic intermediate) were studied by thermal analysis and powder X-ray diffraction. High-performance liquid chromatography and gas chromatography methods were used for the chemical purity and residual solvents determination. In order to study the polymorphic and chemical stability of the amorphous and hemipentahydrate forms, a hygroscopicity test (25 °C, 80% RH) was performed. Powder diffraction and high-performance liquid chromatography analyses revealed that the amorphous character and high chemical purity were preserved after the hygroscopicity test. The hemipentahydrate form transformed completely to the heptahydrate form of pemetrexed disodium. Both pemetrexed disodium forms were produced with high efficiency and pharmaceutical purity in a small commercial scale. Amorphous pemetrexed disodium was selected for further pharmaceutical development. Two new polymorphs (forms 1 and 2) of pemetrexed diacid were used for the preparation of high purity amorphous pemetrexed disodium.

Identification and physicochemical characteristics of temozolomide process-related impurities.

In this article the crystal structures of the starting material TZ-5 and the key intermediate TZ-6 of temozolomide (TZ-7), an anticancer therapeutic agent, are presented, together with their spectroscopic and thermal characteristics. Both compounds crystallize in the triclinic P-1 space group. X-ray crystallography studies proved that the compound TZ-6 exists as a monohydrate. A complete structural assignment was obtained for the signals in the 1H-, 13C- and 15N-nuclear magnetic resonance spectra and the structures were confirmed by Fourier-Transform infrared and Raman spectroscopy. The article describes the importance of the high purity of TZ-6 during the small-scale plant production of TZ-7 in a desired polymorphic form III with the purity higher than 99.50%, according to an HPLC method.

Stability of sample solution as a crucial point during HPLC determination of chemical purity of temozolomide drug substance.

An HPLC method for determination of related substances in temozolomide drug substance was developed. Particular attention was paid to the stability studies due to the fact that temozolomide is unstable in a solution and quickly decomposes to its main degradation product 5-amino-4-imidazolecarboxamide (AIC). A mixture of diluted acetic acid and acetonitrile (4:1, v/v) as a diluent guaranteed lowering the decomposition of temozolomide in the solution. As it is not practically possible to fully eliminate the decomposition of temozolomide during an analysis, the mathematical correction of the results was proposed which allows to analyse almost five times more samples per week, comparing to the procedure without the application of the correction. The accuracy of the correction procedure was proved by investigating the recovery of AIC spiked to temozolomide solutions at different levels. Recoveries equalled 90-108% for AIC concentrations contained in the range of 0.30-1.80 µg ml(-1). The developed method was validated according to the current guidelines, proving the suitability of the method for its intended purpose.

Preparation, purification and regioselective functionalization of protoescigenin--the main aglycone of escin complex.

A two-step chemical process for controlled degradation of escin, affording a mixture of olean-12-ene sapogenins, was elaborated and scaled up. The main component of the mixture--protoescigenin--was isolated and purified, in the form of its corresponding monohydrate, without resource to chromatographic methods. This material was further converted into the high purity 3,24;16,22-di-O,O-isopropylidene derivative in a validated large scale laboratory process.

Physicochemical characteristics of sunitinib malate and its process-related impurities.

In this article, details of crystal and molecular structures of sunitinib malate (SUM), an anticancer therapeutic, and its key synthetic intermediate are presented. Both these compounds were also characterized spectroscopically and thermally. SUM crystallizes in the monoclinic P2(1) space group with two molecules in the asymmetric part of the unit cell, whereas the intermediate crystallises in the triclinic P-1 space group with four independent molecules in the asymmetric unit. The three-dimensional structure of SUM consists of two different layers of molecules. The first one is built of the malic anions, whereas the other layer consists of more hydrophobic sunitinib molecules. This layer is formed by two types of molecules creating a herring bond-like pattern with pairs of neighboring cations forming the V-shape arrangement of molecules. The V-shaped pairs of molecules form ribbons by fitting into two neighboring V shapes. The characteristic V-shape assemble of the moieties is hold together with three C-H…F weak interactions. Besides, process-related impurities of SUM were identified and their structures confirmed by separate synthesis. These impurities were fully characterized by spectroscopic and crystallographic methods as well as by differential scanning calorimetry and thermogravimetric analysis. The H-, (13)C-, and (15)N-nuclear magnetic resonance signals were fully assigned structurally and the resulting structures were confirmed by Fourier-transformed infrared spectroscopy. It was the herein elaborated synthesis of impurity-free SUM that allowed for growing of its single crystals suitable for X-ray crystallographic studies. Comparison of the powder X-ray diffraction pattern for SUM with that derived from single-crystal X-ray crystallographic analysis indicated that SUM formed the polymorph I crystal phase, which is also encountered in its pharmaceutical formulation.

Distinguishing between polymorphic forms of linezolid by solid-phase electronic and vibrational circular dichroism.

For the first time two crystalline forms of the same compound (linezolid polymorphs) were investigated by means of the solid-phase ECD and VCD spectra. The ECD spectra show distinct differences and the band at 221 nm serves as a diagnostic one because it is present in form II but absent in form III. The VCD spectra strongly differ in the diagnostic carbonyl absorption range exhibiting two relatively strong bands of opposite signs.

Stability studies and structural characterization of pramipexole.

Stability studies of pramipexole dihydrochloride performed under following conditions of temperature and relative humidity (RH): 25 degrees C 60% RH and 40 degrees C 75% RH revealed its tendency to the water sorption and the monohydrate formation. The structural changes occurring during storage were studied by infrared spectroscopy and X-ray powder diffraction methods. The thermogravimetry technique was used to control the water sorption by the substance. Pramipexole dihydrochloride monohydrate was characterized by nuclear magnetic resonance and X-ray single crystal diffraction methods. The monohydrate crystallizes in the orthorhombic crystal system in the space group P212121.

Optimization of aripiprazole synthesis.

A series of aripiprazole (AR3) syntheses were performed at laboratory scale (10 mmol of the ARI substrate) in order to optimize the amount of another substrate AR2, as well as Na2CO3, ethanol and varying the reaction time. The reaction parameters were chosen according to the D-optimal plans. A high conversion ratio, about 90-99%, was obtained. Purity of crude product (AR3) was determined by HPLC. Molar content of crude reaction product was predicted theoretically with the use of the mass balance and the corresponding HPLC parameters. The theoretical predictions were verified with the potentiometric and thermogravimetric analysis of selected samples. Based on the predicted molar content of reaction mixtures, a series of reaction response surfaces was calculated and optimal set of reaction parameters for aripiprazole synthesis was determined.