Development, Analytical Characterization, and Bioactivity Evaluation of Boswellia serrata Extract-Layered Double Hydroxide Hybrid Composites.

Boswellia serrata Roxb. extract (BSE), rich in boswellic acids, is well known as a potent anti-inflammatory natural drug. However, due to its limited aqueous solubility, BSE inclusion into an appropriate carrier, capable of improving its release in the biological target, would be highly desirable. Starting with this requirement, new hybrid composites based on the inclusion of BSE in a lamellar solid layered double hydroxide (LDH), i.e., magnesium aluminum carbonate, were developed and characterized in the present work. The adopted LDH exhibited a layered crystal structure, comprising positively charged hydroxide layers and interlayers composed of carbonate anions and water molecules; thus, it was expected to embed negatively charged boswellic acids. In the present case, a calcination process was also adopted on the LDH to increase organic acid loading, based on the replacement of the original inorganic anions. An accurate investigation was carried out by TGA, PXRD, FT-IR/ATR, XPS, SEM, and LC-MS to ascertain the nature, interaction, and quantification of the active molecules of the vegetal extract loaded in the developed hybrid materials. As a result, the significant disruption of the original layered structure was observed in the LDH subjected to calcination (LDHc), and this material was able to include a higher amount of organic acids when its composite with BSE was prepared. However, in vitro tests on the composites' bioactivity, expressed in terms of antimicrobial and anti-inflammatory activity, evidenced LDH-BSE as a better material compared to BSE and to LDHc-BSE, thus suggesting that, although the embedded organic acid amount was lower, they could be more available since they were not firmly bound to the clay. The composite was able to significantly decrease the number of viable pathogens such as Escherichia coli and Staphylococcus aureus, as well as the internalization of toxic active species into human cells imposing oxidative stress, in comparison to the BSE.

3D printed mucoadhesive orodispersible films manufactured by direct powder extrusion for personalized clobetasol propionate based paediatric therapies.

The aim of this work is the development and production by Direct Powder Extrusion (DPE) 3D printing technique of novel oral mucoadhesive films delivering Clobetasol propionate (CBS), useful in paediatric treatment of Oral Lichen Planus (OLP), a rare chronic disease. The DPE 3D printing of these dosage forms can allow the reduction of frequency regimen, the therapy personalization, and reduction of oral cavity administration discomfort. To obtain suitable mucoadhesive films, different polymeric materials, namely hydroxypropylmethylcellulose or polyethylene oxide blended with chitosan (CS), were tested and hydroxypropyl-ß-cyclodextrin was added to increase the CBS solubility. The formulations were tested in terms of mechanical, physico-chemical, and in vitro biopharmaceutical properties. The film showed a tenacious structure, with drug chemical-physical characteristics enhancement due to its partial amorphization during the printing stage and owing to cyclodextrins multicomponent complex formation. The presence of CS enhanced the mucoadhesive properties leading to a significant increase of drug exposure time on the mucosa. Finally, the printed films permeation and retention studies through porcine mucosae showed a marked retention of the drug inside the epithelium, avoiding drug systemic absorption. Therefore, DPE-printed films could represent a suitable technique for the preparation of mucoadhesive film potentially usable for paediatric therapy including OLP.

CrystalMELA: a new crystallographic machine learning platform for crystal system determination.

Determination of the crystal system and space group is the first step of crystal structure analysis. Often this turns out to be a bottleneck in the material characterization workflow for polycrystalline compounds, thus requiring manual interventions. This work proposes a new machine-learning (ML)-based web platform, CrystalMELA (Crystallography MachinE LeArning), for crystal systems classification. Two different ML models, random forest and convolutional neural network, are available through the platform, as well as the extremely randomized trees algorithm, available from the literature. The ML models learned from simulated powder X-ray diffraction patterns of more than 280 000 published crystal structures from organic, inorganic and metal-organic compounds and minerals which were collected from the POW_COD database. A crystal system classification accuracy of 70%, which improved to more than 90% when considering the Top-2 classification accuracy, was obtained in tenfold cross-validation. The validity of the trained models has also been tested against independent experimental data of published compounds. The classification options in the CrystalMELA platform are powerful, easy to use and supported by a user-friendly graphic interface. They can be extended over time with contributions from the community. The tool is freely available at https://www.ba.ic.cnr.it/softwareic/crystalmela/ following registration.

Direct cyclodextrin based powder extrusion 3D printing of budesonide loaded mini-tablets for the treatment of eosinophilic colitis in paediatric patients.

The purpose of this study was to combine direct powder extrusion (DPE) 3D printing and fluid bed coating techniques to create a budesonide (BD) loaded solid oral formulations for the treatment of eosinophilic colitis (EC) in paediatric patients. The preferred medication for EC treatment is BD, which has drawbacks due to its poor water solubility and low absorption. Additionally, since commercially available medications for EC treatment are created and approved for adult patients, administering them to children sometimes requires an off-label use and an impromptu handling, which can result in therapeutic ineffectiveness. The DPE 3D approach was investigated to create Mini-Tablets (MTs) to suit the swallowing, palatability, and dose flexibility control requirements needed by paediatric patients. Additionally, DPE 3D and the inclusion of hydroxypropyl-ß-cyclodextrin in the initial powder mixture allowed for an improvement in the solubility and rate of BD dissolution in aqueous medium. Then, to accomplish a site-specific drug release at the intestinal level, MTs were coated with a layer of Eudragit FS 30D, an enteric polymer responsive at pH > 7.0 values. In vitro release experiments showed that film-coated MTs were suitable in terms of size and dose, enabling potential therapeutic customization and targeted delivery of BD to the colon.

Colonic budesonide delivery by multistimuli alginate/Eudragit® FS 30D/inulin-based microspheres as a paediatric formulation.

The purpose of this study was to develop an oral paediatric formulation of budesonide (BUD) for the treatment of inflammatory bowel disease. A formulation realized as microspheres using the prilling/vibration technique is proposed as an innovative drug delivery system ensuring BUD-specific colonic release in response to different triggers, such as pH, transit time, and resident microbiota. BUD, or the inclusion complex BUD/hydroxypropyl-ß-cyclodextrin, was loaded into microspheres consisting of different ratios of alginate, Eudragit® FS 30D, with or without inulin. Sixteen formulations are produced that show high yields and encapsulation efficiencies, ensuring a homogenous distribution of BUD into the matrix. Microsphere diameters of <655 µm and promising flow properties make these systems suitable for oral administration to children. Swelling and drug release studies in simulated gastrointestinal fluid are used to demonstrate the response of microspheres to time and pH triggers. Studies in faecal medium highlight that drug release from microspheres with inulin is also influenced by microbiota.

Direct cyclodextrin-based powder extrusion 3D printing for one-step production of the BCS class II model drug niclosamide.

Niclosamide (NCS) is a drug that has been used as an anthelmintic and anti-parasitic drug for about 40 years. Recently, some studies have highlighted its potential in treating various tumors, allowing a repositioning of this drug. Despite its potential, NCS is a Biopharmaceutical Classification System (BCS) Class II drug and is consequently characterized by low aqueous solubility, poor dissolution rate and reduced bioavailability, which limits its applicability. In this work, we utilize a very novel technique, direct powder extrusion (DPE) 3D printing, which overcomes the limitations of previously used techniques (fused deposition modelling, FDM) to achieve direct extrusion of powder mixtures consisting of NCS, hydroxypropyl methylcellulose (HPMC, Affinisol 15 LV), hydroxypropyl-ß-cyclodextrin (HP-ß-CD) and polyethylene glycol (PEG) 6000. For the first time, direct printing of powder blends containing HP-ß-CD was conducted. For all tablets, in vitro dissolution studies showed sustained drug release over 48 h, but for tablets containing HP-ß-CD, the release was faster. Solid-state characterization studies showed that during extrusion, the drug lost its crystal structure and was evenly distributed within the polymer matrix. All printed tablets have exhibited good mechanical and physical features and a stability of the drug content for up to 3 months. This innovative printing technique has demonstrated the possibility to produce personalized pharmaceutical forms directly from powders, avoiding the use of filament used by FDM.

Structural Behavior and Spin-State Features of BaAl2O4 Scaled through Tuned Co3+ Doping.

Pure and Co3+-doped BaAl2O4 [Ba(Al1-xCox)2O4, x = 0, 0.0077, 0.0379] powder samples were prepared by a facile hydrothermal route. Elemental analyses by static secondary ion mass spectrometry (SIMS), X-ray absorption spectroscopy (XAS) measurements at the Co K-edge, and X-ray diffraction studies were fully correlated, thus addressing a complete description of the structural complexity of Co3+-doped BaAl2O4 powder. Powder X-ray diffraction (PXRD) patterns indicated that prepared samples were nanocrystalline with a hexagonal P63 symmetry. The X-ray absorption near-edge structure (XANES) measurements revealed the presence of cobalt in a +3 oxidation state, while the rarely documented, tetrahedral symmetry around Co3+ was extracted from the extended X-ray absorption fine structure (EXAFS) oscillation patterns. Rietveld structure refinements showed that Co3+ preferentially substitutes Al3+ at tetrahedral Al3 sites of the BaAl2O4 host lattice, whereas the (Al3)O4 tetrahedra remain rather regular with Co3+-O distances ranging from 1.73(9) to 1.74(9) Å. The underlying magneto-structural features were unraveled through axial and rhombic zero-field splitting (ZFS) terms. The increased substitution of Al3+ by Co3+ at Al3 sites leads to an increase of the axial ZFS terms in Co3+-doped BaAl2O4 powder from 10.8 to 26.3 K, whereas the rhombic ZFS parameters across the series change in the range from 2.7 to 10.4 K, showing a considerable increase of anisotropy together with the values of the anisotropic g-tensor components flowing from 1.7 to 2.5. We defined the line between the Co3+ doping limit and influenced magneto-structural characteristics, thus enabling the design of strategy to control the ZFS terms' contributions to magnetic anisotropy within Co3+-doped BaAl2O4 powder.

Structural Insights into the Vapochromic Behavior of Pt- and Pd-Based Compounds.

Anionic complexes having vapochromic behavior are investigated: [K(H2O)][M(ppy)(CN)2], [K(H2O)][M(bzq)(CN)2], and [Li(H2O)n][Pt(bzq)(CN)2], where ppy = 2-phenylpyridinate, bzq = 7,8-benzoquinolate, and M = Pt(II) or Pd(II). These hydrated potassium/lithium salts exhibit a change in color upon being heated to 380 K, and they transform back into the original color upon absorption of water molecules from the environment. The challenging characterization of their structure in the vapochromic transition has been carried out by combining several experimental techniques, despite the availability of partially ordered and/or impure crystalline material. Room-temperature single-crystal and powder X-ray diffraction investigation revealed that [K(H2O)][Pt(ppy)(CN)2] crystallizes in the Pbca space group and is isostructural to [K(H2O)][Pd(ppy)(CN)2]. Variable-temperature powder X-ray diffraction allowed the color transition to be related to changes in the diffraction pattern and the decrease in sample crystallinity. Water loss, monitored by thermogravimetric analysis, occurs in two stages, well separated for potassium Pt compounds and strongly overlapped for potassium Pd compounds. The local structure of potassium compounds was monitored by in situ pair distribution function (PDF) measurements, which highlighted changes in the intermolecular distances due to a rearrangement of the crystal packing upon vapochromic transition. A reaction coordinate describing the structural changes was extracted for each compound by multivariate analysis applied to PDF data. It contributed to the study of the kinetics of the structural changes related to the vapochromic transition, revealing its dependence on the transition metal ion. Instead, the ligand influences the critical temperature, higher for ppy than for bzq, and the inclination of the molecular planes with respect to the unit cell planes, higher for bzq than for ppy. The first stage of water loss triggers a unit cell contraction, determined by the increase in the b axis length and the decrease in the a (for ppy) or c (for bzq) axis lengths. Consequent interplane distance variations and in-plane roto-translations weaken the π-stacking of the room-temperature structure and modify the distances and angles of Pt(II)/Pd(II) chains. The curve describing the intermolecular Pt(II)/Pd(II) distances as a function of temperature, validated by X-ray absorption spectroscopy, was found to reproduce the coordinate reaction determined by the model-free analysis.

Xanthenylacetic Acid Derivatives Effectively Target Lysophosphatidic Acid Receptor 6 to Inhibit Hepatocellular Carcinoma Cell Growth.

Despite the increasing incidence of hepatocellular carcinoma (HCC) worldwide, current pharmacological treatments are still unsatisfactory. We have previously shown that lysophosphatidic acid receptor 6 (LPAR6) supports HCC growth and that 9-xanthenylacetic acid (XAA) acts as an LPAR6 antagonist inhibiting HCC growth without toxicity. Here, we synthesized four novel XAA derivatives, (±)-2-(9H-xanthen-9-yl)propanoic acid (compound 4 - MC9), (±)-2-(9H-xanthen-9-yl)butanoic acid (compound 5 - MC6), (±)-2-(9H-xanthen-9-yl)hexanoic acid (compound 7 - MC11), and (±)-2-(9H-xanthen-9-yl)octanoic acid (compound 8 - MC12, sodium salt) by introducing alkyl groups of increasing length at the acetic α-carbon atom. Two of these compounds were characterized by X-ray powder diffraction and quantum mechanical calculations, while molecular docking simulations suggested their enantioselectivity for LPAR6. Biological data showed anti-HCC activity for all XAA derivatives, with the maximum effect observed for MC11. Our findings support the view that increasing the length of the alkyl group improves the inhibitory action of XAA and that enantioselectivity can be exploited for designing novel and more effective XAA-based LPAR6 antagonists.

Exploring new hydrated delta type vanadium oxides for lithium intercalation.

Three hydrated double layered vanadium oxides, namely Na0.35V2O5·0.8(H2O), K0.36(H3O)0.15V2O5 and (NH4)0.37V2O5·0.15(H2O), were obtained by using mild hydrothermal conditions. Their delta type structural frameworks were solved by high-resolution synchrotron X-ray powder diffraction and the interlayer spacings were interpreted from difference Fourier maps. The inter-slab distances are modulated by the water content and the special arrangements of the alkali and ammonium cations. The XPS measurements denote mixed valence systems with high contents of V4+ ions up to 40%. The monitoring of the V4+ EPR signal over time suggests a reduction of the electronic delocalization on account of the partial oxidation to V5+. The electrochemical performance of the active phases is strongly conditioned by the vacuum-drying process of the electrodes, showing better capacity retention when vacuum is not applied. In situ X-ray diffraction shows a structural mechanism of contraction/expansion of the bilayers upon lithium insertion/extraction where the alkali ions behave as structural stabilizers. Galvanostatic cycling at very low current density implies migration of the alkali "pillars" triggering the collapse of the structure.

Crystallographic study of PET radio-tracers in clinical evaluation for early diagnosis of Alzheimers.

The title compound, C24H25NO3·2CH3OH, which crystallized as a methanol disolvate, has applications as a PET radiotracer in the early diagnosis of Alzheimer's disease. The dihedral angle between the biphenyl rings is 8.2 (2)° and the heterocyclic ring adopts a half-chair conformation with the N atom adopting a pyramidal geometry (bond-angle sum = 327.6°). The C atoms of both meth-oxy groups lie close to the plane of their attached ring [deviations = 0.107 (6) and 0.031 (6) Å]. In the crystal, the components are linked by O-H⋯O and O-H⋯N hydrogen bonds, generating [010] chains. C-H⋯O inter-actions are also observed.

Harnessing the ortho-directing ability of the azetidine ring for the regioselective and exhaustive functionalization of arenes.

This work demonstrates how the directing ability of the azetidine ring could be useful for regioselective ortho-C-H functionalization of aryl compounds. Robust polar organometallic (lithiated) intermediates are involved in this synthetic strategy. The reagent n-hexyllithium emerged as a safer, yet still effective, basic reagent for the hydrogen/lithium permutation relative to the widely used reagent nBuLi. Two different reaction protocols were discovered for regioselective lithiation at the ortho positions adjacent to the azetidine ring, which served as a toolbox when other competing directing groups were installed on the aromatic ring. The coordinating ability of the azetidine nitrogen atom, as well as the involvement of dynamic phenomena related to the preferential conformations of 2-arylazetidine derivatives, were recognized to be responsible for the observed reactivity and regioselectivity. A site-selective functionalization of the aromatic ring was achieved for aryl azetidines with either coordinatively competent groups (e.g. methoxy) or inductively electron-withdrawing substituents (e.g. chlorine and fluorine). By fine-tuning the reaction conditions, regioselective introduction of several substituents on the aromatic ring could be realized. Several substitution patterns were accomplished, which included 1,2,3-trisubstitution, 1,2,3,4-tetrasubstitution, and 1,2,3,4,5-pentasubstitution, up to the exhaustive substitution of the aromatic ring.

Covariance and correlation estimation in electron-density maps.

Quite recently two papers have been published [Giacovazzo & Mazzone (2011). Acta Cryst. A67, 210-218; Giacovazzo et al. (2011). Acta Cryst. A67, 368-382] which calculate the variance in any point of an electron-density map at any stage of the phasing process. The main aim of the papers was to associate a standard deviation to each pixel of the map, in order to obtain a better estimate of the map reliability. This paper deals with the covariance estimate between points of an electron-density map in any space group, centrosymmetric or non-centrosymmetric, no matter the correlation between the model and target structures. The aim is as follows: to verify if the electron density in one point of the map is amplified or depressed as an effect of the electron density in one or more other points of the map. High values of the covariances are usually connected with undesired features of the map. The phases are the primitive random variables of our probabilistic model; the covariance changes with the quality of the model and therefore with the quality of the phases. The conclusive formulas show that the covariance is also influenced by the Patterson map. Uncertainty on measurements may influence the covariance, particularly in the final stages of the structure refinement; a general formula is obtained taking into account both phase and measurement uncertainty, valid at any stage of the crystal structure solution.

Diarylheterocycle core ring features effect in selective COX-1 inhibition.

The COX-1 isoenzyme plays a significant role in a variety of diseases, as it catalyzes the bioprocesses behind many health problems. Among the diarylheterocycle class of COX inhibitors, the isoxazole ring has been widely used as a central heterocycle for the preparation of potent and selective COX-1 inhibitors such as P6 [3-(5-chlorofuran-2-yl)-5-methyl-4-phenylisoxazole]. The role of the isoxazole nucleus in COX-1 inhibitor selectivity has been clarified by preparing a set of new diarylheterocycles with various heterocycle cores. Replacement of isoxazole with isothiazole or pyrazole gave a drastic decrease in COX-1 inhibitory activity, whereas the introduction of an electron-donating group (EDG) on the N-aryl pyrazole allowed recovery of COX-1 inhibitory activity and selectivity. The EDG-equipped 5-(furan-2-yl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole (17) selectively inhibits COX-1 activity (IC(50) =3.4 µM; 28% COX-2 inhibition at 50 µM), in contrast to its inactive analogue, 3-(furan-2-yl)-1-phenyl-5-(trifluoromethyl)-1H-pyrazole, which does not bear the methoxy EDG. Molecular docking studies of compound 17 into the binding site of COX-1 shed light on its binding mode.

Nitrogen dynamics and reactivity of chiral aziridines: generation of configurationally stable aziridinyllithium compounds.

Diastereomeric oxazolinylaziridines (R,R)-9 and (R,S)-9 have been regioselectively lithiated at the α-position with respect to the oxazolinyl ring. The resulting aziridinyllithium compounds proved to be chemically and configurationally stable under the experimental conditions used, thus furnishing, upon trapping with electrophiles, chiral 2,2-disubstituted aziridines, in contrast to the corresponding α-lithiated oxazolinyloxiranes that have been reported to be chemically stable but configurationally unstable. This peculiar behavior of the nitrogen-bearing heterocycle has been rationalized on the basis of DFT calculations and the observed dynamics of the aziridine nitrogen atom. The DFT analysis allowed the disclosure of a solvent-dependent differing stability of diastereomeric lithiated aziridines (R,R)-9-Li and (R,S)-9-Li, suggesting η(3)-coordinated oxazolinylaziridinyllithium compounds as likely intermediates. Such intermediates could be the result of a dynamically controlled lithiation that relies on the preliminary formation of a complex between the lithiating agent and the oxazolinyl ring. According to this model, the competing complexation of the lithiating agent by the lone pair of electrons on the aziridine nitrogen would cause addition to the oxazoline C=N bond, thus ending up with the formation of oxazolidines, which are precursors of useful chiral ketoaziridines. The proposed model has been also supported by estimating the nitrogen inversion barrier by dynamic NMR spectroscopic experiments.

MAD techniques applied to powder data: finding the structure given the substructure.

The joint probability distribution function method is applied to multiple-wavelength anomalous dispersion (MAD) powder data. The distributions are calculated by assuming prior knowledge of the scattering intensities at two wavelengths and of the anomalous-scatterer substructure. The method leads to formulas estimating the full structure phases and their reliability. The procedure has been applied to two structures, one unknown and one known; the second was used as a control for the phasing procedure. In spite of the unavoidable peak overlapping in the diffraction pattern, the formulas proved to be very effective. Combined with a new algorithm for phase extension, they enabled the solution of both crystal structures.

Correcting electron-density resolution bias in reciprocal space.

Fourier syntheses are always affected by series-termination errors, which generate sets of positive and negative ripples around each main peak in the map. The interaction among the ripples distorts the profile of the map and moves peaks away from their correct positions. In a previous paper [Altomare et al. (2008). Acta Cryst. A64, 326-336] an algorithm was described which reduces the resolution bias by removing the effects of the ripples in direct space. In this paper the correction is performed in reciprocal space: the effect of the ripples on the atomic scattering factors is calculated and subtracted from the usual atomic scattering factors. The modified scattering factors are used to calculate new structure factors, from which more accurate electron-density maps may be obtained. The experimental tests show that the procedure minimizes the effects of the resolution bias and provides atomic positions that are more accurate than those provided by traditional approaches.

Minimally resolution biased electron-density maps.

Electron-density maps are calculated by Fourier syntheses with coefficients based on structure factors. Diffraction experiments provide intensities up to a limited resolution; as a consequence, the Fourier syntheses always show series-termination errors. The worse the resolution, the less accurate is the Fourier representation of the electron density. In general, each atomic peak is shifted from the correct position, shows a deformed (with respect to the true distribution of the electrons in the atomic domain) profile, and is surrounded by a series of negative and positive ripples of gradually decreasing amplitude. An algorithm is described which is able to reduce the resolution bias by relocating the peaks in more correct positions and by modifying the peak profile to better fit the real atomic electron densities. Some experimental tests are performed showing the usefulness of the procedure.

Direct Methods Optimised for Solving Crystal Structure by Powder Diffraction Data: Limits, Strategies, and Prospects.

The ab-initio crystal structure solution by powder diffraction data requires great efforts because of the collapse of the experimental information onto the one dimensional 2θ axis of the pattern. Different strategies will be described aiming at improving the process of extraction of the integrated intensities from the experimental pattern in order to make more straightforward the structure solution process by direct methods. Particular attention will be devoted to the EXPO program. Some of its performance will be analysed and results will be shown.