17-β-Estradiol-β-Cyclodextrin Complex as Solid: Synthesis, Structural and Physicochemical Characterization

17-β-estradiol (EST) is the most potent form of naturally occurring estrogens; therefore, it has found a wide pharmaceutical application. The major problem associated with the use of EST is its very low water solubility, resulting in poor oral bioavailability. To overcome this drawback, a complexation with cyclodextrins (CD) has been suggested as a solution. In this work, the host-guest inclusion complex between the ß-CD and EST has been prepared using four different methods. The obtained samples have been deeply characterized using ¹³C CP MAS solid state NMR, PXRD, FT-IR, TGA, DSC, and SEM. Using SCXRD, the crystal structure of the complex has been determined, being to the best of our knowledge the first solved crystal structure of an estrogen/CD complex. The periodic DFT calculations of NMR properties using GIPAW were found to be particularly helpful in the analysis of disorder in the solid state and interpretation of experimental NMR results. This work highlights the importance of a combined ssNMR/SCXRD approach to studying the structure of the inclusion complexes formed by cyclodextrins.

Dual-Stimuli-Sensitive Smart Hydrogels Containing Magnetic Nanoparticles as Antitumor Local Drug Delivery Systems-Synthesis and Characterization

The aim of this study was to develop an innovative, dual-stimuli-responsive smart hydrogel local drug delivery system (LDDS), potentially useful as an injectable simultaneous chemotherapy and magnetic hyperthermia (MHT) antitumor treatment device. The hydrogels were based on a biocompatible and biodegradable poly(ε-caprolactone-co-rac-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-rac-lactide) (PCLA-PEG-PCLA, PCLA) triblock copolymer, synthesized via ring-opening polymerization (ROP) in the presence of a zirconium(IV) acetylacetonate (Zr(acac)₄) catalyst. The PCLA copolymers were successfully synthesized and characterized using NMR and GPC techniques. Furthermore, the gel-forming and rheological properties of the resulting hydrogels were thoroughly investigated, and the optimal synthesis conditions were determined. The coprecipitation method was applied to create magnetic iron oxide nanoparticles (MIONs) with a low diameter and a narrow size distribution. The magnetic properties of the MIONs were close to superparamagnetic upon TEM, DLS, and VSM analysis. The particle suspension placed in an alternating magnetic field (AMF) of the appropriate parameters showed a rapid increase in temperature to the values desired for hyperthermia. The MIONs/hydrogel matrices were evaluated for paclitaxel (PTX) release in vitro. The release was prolonged and well controlled, displaying close to zero-order kinetics; the drug release mechanism was found to be anomalous. Furthermore, it was found that the simulated hyperthermia conditions had no effect on the release kinetics. As a result, the synthesized smart hydrogels were discovered to be a promising antitumor LDDS, allowing simultaneous chemotherapy and hyperthermia treatment.

Hydrogels Based on Poly(Ether-Ester)s as Highly Controlled 5-Fluorouracil Delivery Systems-Synthesis and Characterization

A novel and promising hydrogel drug delivery system (DDS) capable of releasing 5‑fluorouracil (5-FU) in a prolonged and controlled manner was obtained using ε‑caprolactone‑poly(ethylene glycol) (CL-PEG) or rac‑lactide-poly(ethylene glycol) (rac‑LA-PEG) copolymers. Copolymers were synthesized via the ring-opening polymerization (ROP) process of cyclic monomers, ε‑caprolactone (CL) or rac-lactide (rac-LA), in the presence of zirconium(IV) octoate (Zr(Oct)₄) and poly(ethylene glycol) 200 (PEG 200) as catalyst and initiator, respectively. Obtained triblock copolymers were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) techniques; the structure and tacticity of the macromolecules were determined. The relationship between the copolymer structure and the reaction conditions was evaluated. The optimal conditions were specified as 140 °C and 24 h. In the next step, CL-PEG and rac-LA-PEG copolymers were chemically crosslinked using hexamethylene diisocyanate (HDI). Selected hydrogels were subjected to in vitro antitumor drug release studies, and the release data were analyzed using zero-order, first-order, and Korsmeyer-Peppas mathematical models. Controlled and prolonged (up to 432 h) 5-FU release profiles were observed for all examined hydrogels with first-order or zero-order kinetics. The drug release mechanism was generally denoted as non-Fickian transport.

Pharmaceutical Hydrates Analysis-Overview of Methods and Recent Advances

This review discusses a set of instrumental and computational methods that are used to characterize hydrated forms of APIs (active pharmaceutical ingredients). The focus has been put on highlighting advantages as well as on presenting some limitations of the selected analytical approaches. This has been performed in order to facilitate the choice of an appropriate method depending on the type of the structural feature that is to be analyzed, that is, degree of hydration, crystal structure and dynamics, and (de)hydration kinetics. The presented techniques include X-ray diffraction (single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD)), spectroscopic (solid state nuclear magnetic resonance spectroscopy (ssNMR), Fourier-transformed infrared spectroscopy (FT-IR), Raman spectroscopy), thermal (differential scanning calorimetry (DSC), thermogravimetric analysis (TGA)), gravimetric (dynamic vapour sorption (DVS)), and computational (molecular mechanics (MM), Quantum Mechanics (QM), molecular dynamics (MD)) methods. Further, the successful applications of the presented methods in the studies of hydrated APIs as well as studies on the excipients' influence on these processes have been described in many examples.

Smart Hydrogels - Synthetic Stimuli-Responsive Antitumor Drug Release Systems

Among modern drug formulations, stimuli-responsive hydrogels also called "smart hydrogels" deserve a special attention. The basic feature of this system is the ability to change their mechanical properties, swelling ability, hydrophilicity, bioactive molecules permeability, etc., influenced by various stimuli, such as temperature, pH, electromagnetic radiation, magnetic field and biological factors. Therefore, stimuli-responsive matrices can be potentially used in tissue engineering, cell cultures and technology of innovative drug delivery systems (DDSs), releasing the active substances under the control of internal or external stimuli. Moreover, smart hydrogels can be used as injectable DDSs, due to gel-sol transition connected with in situ cross-linking process. Innovative smart hydrogel DDSs can be utilized as matrices for targeted therapy, which enhances the effectiveness of tumor chemotherapy and subsequently limits systemic toxicity. External stimulus sensitivity allows remote control over the drug release profile and gel formation. On the other hand, internal factors provide drg accumulation in tumor tissue and reduce the concentration of active drug form in healthy tissue. In this report, we summarise the basic knowledge and chemical strategies for the synthetic smart hydrogel DDSs applied in antitumor therapy.

Determination of the elemental composition and antioxidant properties of dates (Phoenix dactyliferia) originated from different regions

Due to the growing interest in running a healthy life, including the diet a special interest has been put in searching for products that are rich in nutrients, macro and micronutrients and vitamins. Dates are the fruits that meet these requirements and show multidirectional pro-health effects. These fruits are a source of potassium and other macro- and micronutrients. They have antioxidant properties thanks to the content of flavonoids and polyphenols. The elemental composition (Al, Ca, Cu, Fe, K, Mg, Mn, P, Sr and Zn) and antioxidant properties (total equivalent antioxidant capacity, total polyphenol content, total flavonoid content) of various dates from different regions of the world was determined. The results have shown that the peel and flesh of dates differ significantly in chemical composition. The peel is significantly richer in chemical components of biological importance. Discriminant analysis of the results obtained for dates originated from various regions indicated that the main factor determining the tested chemical composition is the place of cultivation, not the variety.

Application of combined solid-state NMR and DFT calculations for the study of piracetam polymorphism

Piracetam, a popular nootropic drug, widely used in the treatment of age-associated mental decline and disorders of the nervous system such as Alzheimer's disease and dementia exists under normal pressure in three polymorphic forms (P1, P2 and P3) of different stability. In this work the relative stability of piracetam polymorphs depending on the temperature was studied using the ssNMR spectroscopy combined with ab initio DFT calculations. The ssNMR spectroscopy enabled the analysis of polymorphic phase transition in the case of pure active substance as well as polymorphic form identification in the analysis of the commercial solid dosage formulations. Quantum chemical calculations of phonon density of states were performed to obtain the temperature dependence of the enthalpy, entropy and free energy of the piracetam polymorphs in a quasi-harmonic approximation. GIPAW NMR calculations combined with molecular dynamics were performed to support the chemical shift assignment. The obtained results showed that DFT calculations can be used not only to obtain the NMR parameters but also to predict the influence of the temperature on the stability order of the polymorphic forms of molecular crystals.

How does the NMR thermometer work? Application of combined quantum molecular dynamics and GIPAW calculations into the study of lead nitrate

Lead nitrate is an inorganic salt, commonly used for the accurate temperature determination in the solid state NMR spectroscopy, due to the strong temperature dependence of the ²⁰⁷ Pb chemical shift. As the reason for this phenomenon remained unknown, the main purpose of this study was to explain this temperature dependence at the molecular level. To achieve this, combined CASTEP geometry optimization, quantum molecular dynamics at chosen temperatures and GIPAW NMR computations were performed. Due to the previous literature reports on inaccuracy in the calculation of ²⁰⁷ Pb NMR parameters using GIPAW, a large emphasis was put on the optimization of computational method. The application of quantum molecular dynamics provided the simulation of the temperature-dependent vibrational motions and enabled to accurately compute the changes in the value of Pb δ_iso resulting from them. © 2018 Wiley Periodicals, Inc.

Comment on “Trimorphs of a pharmaceutical cocrystal involving two active pharmaceutical ingredients: potential relevance to combination drugs” by S. Aitipamula, P. S. Chow and R. B. H. Tan, CrystEngComm, 2009, , 1823

This is a commentary on a paper by S. Aitipamula et al. (CrystEngComm, 2009, 11, 1823–1827) on the detailed analysis of the stability of trimorphic cocrystals.

Chemical profile, antioxidant activity and cytotoxic effect of extract from leaves of Erythrochiton brasiliensis Nees & Mart. from different regions of Europe

The total phenolic content (TPC), total tannin content (TTC) and total flavonoid content (TFC) as well as the antioxidant activity and the cytotoxic effect of the extract from leaves of Erythrochiton brasiliensis Nees & Mart. (Rutaceae) were evaluated. Raw material was collected in different European botanical gardens. Statistical analysis revealed a clear grouping of populations according to their climatic zone. The average TPC, TTC and TFC in tested samples were 35.92 (± 7.11) mg GAE·g–1 DW, 14.98 (± 4.08) mg PyE·g–1 DW and 2.92 (± 0.76) mg QuE·g–1 DW, respectively. The scavenged DPPH and Trolox equivalents determined by EPR spectroscopy were 1.23–4.14 and 0.50–1.44 mmol·g–1 of dry extract, respectively. Thirteen compounds (derivatives of bezoic acid acid and trans-cinnammic acid) were identified in the samples. The flavonoid vitexin was also present as the major component in three investigated samples. The in vitro cytotoxicity test of the extract on Vero cells provided IC50 and IC10 values of 175.6 and 72.5 μg·mL–1, respectively. Incubation of samples with HHV-1 infected Vero cells had no effect on the occurrence of cytopathic effect.

Spectroscopic and structural studies of the diosmin monohydrate and anhydrous diosmin

Diosmin, a flavone glycoside frequently used in therapy of various veins diseases in monohydrate form, exhibits poor solubility in water and low bioavailability. Due to the fact that the anhydrous forms of drugs generally have better bioavailability than the corresponding hydrates, the aim of this study was to analyze the conversion of diosmin monohydrate (DSNM) to anhydrous diosmin (DSNA) that occurs upon heating. The mechanism of this transformation was examined as well as advanced structural studies of each form were performed using 13C CP/MAS SSNMR, DSC, FT-IR and PXRD techniques. Spectroscopic findings were supported by CASTEP-DFT calculations of NMR and IR parameters. The pathway of reversible transformation was specified as follows: DSNM upon heating for 24h at temperature up to 110°C losses non-crystalline water and converts into metastable form (DSNM*) that turns into DSNA during heating at temperature 140°C for next 24h. Under room temperature DSNA spontaneously absorbs moisture from air and turns into a DSNM within 72h. The detailed analysis of CP kinetic parameters (T1ρI) revealed presence of metastable, intermediate form of diosmin (DSNM*) and allowed its characterization. The results are essential for further studies comparing dissolution and bioavailability of DSNM and DSNA. The study provided an understanding of the conversion pathway of the diosmin monohydrate into its anhydrate form when it is exposed to increased temperature.

Application of 13C NMR cross-polarization inversion recovery experiments for the analysis of solid dosage forms

Solid-state nuclear magnetic resonance (ssNMR) is a powerful and unique method for analyzing solid forms of the active pharmaceutical ingredients (APIs) directly in their original formulations. Unfortunately, despite their wide range of application, the ssNMR experiments often suffer from low sensitivity and peaks overlapping between API and excipients. To overcome these limitations, the crosspolarization inversion recovery method was successfully used. The differences in the spin-lattice relaxation time constants for hydrogen atoms T1(H) between API and excipients were employed in order to separate and discriminate their peaks in ssNMR spectra as well as to increase the intensity of API signals in low-dose formulations. The versatility of this method was demonstrated by different examples, including the excipients mixture and commercial solid dosage forms (e.g. granules and tablets).

¹³C solid-state NMR analysis of the most common pharmaceutical excipients used in solid drug formulations Part II: CP kinetics and relaxation analysis

Excipients used in the solid drug formulations differ in their NMR relaxation and (13)C cross-polarization (CP) kinetics parameters. Therefore, experimental parameters like contact time of cross-polarization and repetition time have a major impact on the registered solid state NMR spectra and in consequence on the results of the NMR analysis. In this work the CP kinetics and relaxation of the most common pharmaceutical excipients: anhydrous α-lactose, α-lactose monohydrate, mannitol, sucrose, sorbitol, sodium starch glycolate type A and B, starch of different origin, microcrystalline cellulose, hypromellose, ethylcellulose, methylcellulose, hydroxyethylcellulose, sodium alginate, magnesium stearate, sodium laurilsulfate and Kollidon(®) were analyzed. The studied excipients differ significantly in their optimum repetition time (from 5 s to 1200 s) and T(1ρ)(I) parameters (from 2 ms to 73 ms). The practical use of those differences in the excipients composition analysis was demonstrated on the example of commercially available tablets containing indapamide as an API. The information presented in this article will help to choose the correct acquisition parameters and also will save the time and effort needed for their optimization in the NMR analysis of the solid drug formulations.