Haiyan Qu

Exploring the solid-form landscape of pharmaceutical hydrates: transformation pathways of the sodium naproxen anhydrate-hydrate system.

ABSTRACTPurposeTo understand the transformation pathways amongst anhydrate/hydrate solid forms of sodium naproxen and to highlight the importance of a polymorphic dihydrate within this context.MethodsMulti-temperature dynamic vapour sorption (DVS) analysis combined with variable-humidity X-ray powder diffraction (XRPD) to establish the transformation pathways as a function of temperature and humidity. XRPD and thermogravimetric analysis (TGA) to characterise bulk samples. Monitoring of in-situ dehydration using solid-state 13C CP/MAS spectroscopy.ResultsAt 25°C, anhydrous sodium naproxen (AH) transforms directly to one dihydrate polymorph (DH-II). At 50°C, AH transforms stepwise to a monohydrate (MH) then to the other dihydrate polymorph (DH-I). DH-II transforms to a tetrahydrate (TH) more readily than DH-I transforms to TH. Both dihydrate polymorphs transform to the same MH.ConclusionsThe properties of the polymorphic dihydrate control the transformation pathways of sodium naproxen.

Solvent-mediated amorphous-to-crystalline transformation of nitrendipine in amorphous particle suspensions containing polymers

The amorphous-to-crystalline transformation of nitrendipine was investigated using Raman spectroscopy and X-ray powder diffraction (XRPD). The nucleation and growth rate of crystalline nitrendipine in a medium containing poly (vinyl alcohol) (PVA) and polyethylene glycol (PEG 200) were quantitatively determined using image analysis based on polarized light microscopy. The findings from the image analysis revealed that the transformation process occurred through the dissolution of amorphous drug precipitate followed by the nucleation and growth of the crystalline phase with the amorphous precipitate acting as a reservoir for maintaining the supersaturation. The rates of nucleation and crystal growth of nitrendipine decreased with an increase in PEG 200 concentration in organic phase from 0% to 75% (v/v). Increasing the PVA concentration in water phase from 0.1% to 1.0% (w/w) also decreased the rates of nucleation and crystal growth, however, an increase in PVA concentration from 1.0% to 2.0% (w/w) did not result in a further decrease in the rates of nucleation and crystal growth. An increase in drug concentrations in the organic phase from 10 mg/ml to 30 mg/ml led to faster nucleation rates. However, a further increase in drug concentration to 100mg/ml decelerated the growth of nitrendipine crystals. Combining image analysis of polarized light micrographs together with Raman spectroscopy and XRPD provided an in-depth insight into solid state transformations in amorphous nitrendipine suspensions.

Structural basis for the transformation pathways of the sodium naproxen anhydrate-hydrate system

Relationships between the crystal structures of two polymorphs of sodium naproxen dihydrate and its monohydrate and anhydrate phases provide a basis to rationalize the observed transformation pathways in the sodium (S)-naproxen anhydrate–hydrate system.

Raman spectroscopic imaging of indomethacin loaded in porous silica

Loading of a poorly soluble drug such as indomethacin (IMC) into porous silica particles enhances its dissolution upon administration. The distribution of the different solid forms in which IMC may appear was studied using Raman spectroscopy. Raman mapping of the samples was performed with a Raman microscope equipped with an automated xy-stage. The spectral data were extracted in the range 1500–1750 cm−1, which represents the stretching of the CO bond in the IMC molecule. To alleviate the problem of overlapping peaks in the Raman spectra of the different IMC forms, the spectral data were analyzed using partial least squares (PLS) and principal component analysis (PCA). Despite the problems caused by fluorescence, the method gave valuable information about the occurrence and distribution of the solid forms of IMC. The same approach was utilized for analysis of the heterogeneity of recrystallized IMC samples, and PCA was shown to be capable of revealing the presence of solvates or polymorphs not included in the model.

Guaianolides and a seco-Eudesmane from the Resinous Exudates of Cushion Bush (Leucophyta brownii) and Evaluation of Their Cytostatic and Anti-inflammatory Activity.

A detailed phytochemical investigation of a dichloromethane extract of the resinous exudates of the cushion bush plant (Leucophyta brownii) resulted in the isolation of the new 8,12-guaianolides leucophytalins A (5) and B (6), the new 1,10-seco-eudesmane leucophytalin C (10), six rare 8,12-guaianolides (1-4, 7, and 8), and the xanthanolide tomentosin (9). The structures of all isolated compounds were elucidated on the basis of spectroscopic and spectrometric analyses. The structures of compounds isolated in crystalline form, including leucophytalins A and C, were further confirmed by X-ray crystallography. The crude extract exhibited moderate cytostatic activity against a breast cancer (MCF-7) and human colon cancer (HT-29) cell line with IC₅₀ values of 9.3 and 18 μg/mL, respectively, and anti-inflammatory activity against the macrophage-like cell line RAW 264.7 with IC₅₀ values of 3.9 and 6.1 μg/mL for thromboxane B2 and prostaglandin E2 production, respectively. The isolated compounds were evaluated for their cytostatic activity against MCF-7 and HT-29 cells (1, 3-10) and their anti-inflammatory activity against RAW 264.7 cells (1-10). All isolated compounds are most likely derived from (+)-germacrene A, and a biosynthetic pathway is proposed for these sesquiterpenoids.

Crystallization of a polymorphic hydrate system

Nitrofurantoin can form two monohydrates, which have the same chemical composition and molar ratio of water, but differ in the crystal arrangements. The two monohydrates (hydrates I and II) could be produced independently via evaporative crystallization, where supersaturation and solvent composition were both found to have an effect. Hydrate I showed much slower crystallization than hydrate II. During cooling crystallization, the nucleation and growth of hydrate II was again dominant, consuming all supersaturation and leading to no hydrate I formation. Seeding of hydrate I during cooling crystallization was also applied, but the hydrate I seeds were not able to initiate its nucleation rather than dissolving into crystallizing solution. Although solubility tests revealed that hydrate II is more stable than hydrate I due to its lower solubility (110 +/- 4 and 131 +/- 12 microg/mL for hydrates II and I, respectively), this difference is rather small. Therefore, the small free energy difference between the two hydrates, together with the slow crystallization of hydrate I, both lead to a hindrance of hydrate I formation. Furthermore, the crystal structure of hydrate II demonstrated a higher H-bonding extent than hydrate I, suggesting its more favorable crystallization. This is in good agreement with experimental results.

Purification of artemisinin from quercetin by anti-solvent crystallization

In the present work, anti-solvent crystallization of artemisinin from four different organic solvents (methanol, ethanol, acetonitrile, and acetone) was studied. Water was used as anti-solvent. The effect of an impurity (quercetin) on the performance of anti-solvent crystallization of artemisinin was investigated. The fundamental process data such as solubility of artemisinin in pure organic solvents and their binary mixtures with varying composition water were measured at room temperature. The solubility of quercetin was measured only in pure organic solvents at room temperature. Anti-solvent crystallization experiments were designed based on the fundamental process data determined. Firstly, the anti-solvent crystallization of artemisinin without impurity was performed from all four organic solvents and then the experiments were repeated with addition of an impurity (quercetin) while keeping all other process parameters constant. Two different concentrations of impurity, i.e., 10% and 50% of its solubility, in the respective organic solvents at room temperature were used. The effect of impurity on performance of anti-solvent crystallization was evaluated by comparing the yield and purity of the artemisinin obtained with those in the absence of impurity. Results of the present work demonstrated that the presence of quercetin in the solution does not affect the final yield of artemisinin from the solution of each of four organic solvents used. However, the purity of artemisinin crystals were reduced when quercetin concentration was 50% of its solubility in all solvents studied.

Electrospinnability of Poly Lactic-co-glycolic Acid (PLGA): the Role of Solvent Type and Solvent Composition

ABSTRACTPurposeIn this study, the electrospinnability of poly(lactic-co-glycolic acid) (PLGA) solutions was investigated, with a focus on understanding the influence of molecular weight of PLGA, solvent type and solvent composition on the physical properties of electrospun nanofibers.MethodVarious solvents were tested to dissolve two PLGA grades (50 KDa-RG755, 100 KDa-RG750). The viscoelasticity, surface tension, and evaporation rate of the PLGA solutions were characterized prior to the electrospinning process. The resulting electrospun nanofibers were characterized with respect to the morphology and mechanical properties.ResultsTwo pairs of solvent mixtures, i.e. dimethylformamide (DMF)—tetrahydrofuran (THF) and DMF—chloroform (CHL), were identified to provide a stable cone-jet. Within the polymer concentration range studied (10–30%, w/v), RG750 solutions could be electrospun into uniform fibers at 30% (w/v) or at 20% (w/v) when modifying the solvent composition. In comparison to DMF-THF solution, fibers had larger diameter, higher stiffness and tensile strength when electrospun from DMF-CHL solution.ConclusionThe high molecular weight polymer could ensure sufficient intermolecular interaction to generate uniform fibers. The solvent could influence the morphology and mechanical properties of the electrospun fibers by altering the properties of PLGA solution, and drying rate of fibers in the electrospinning process.

Ciprofloxacin-loaded sodium alginate/poly (lactic-co-glycolic acid) electrospun fibrous mats for wound healing

Graphical abstract Figure. No Caption available. Abstract Wound dressings should ideally be able to maintain high humidity, remove excess wound exudate, permit thermal insulation, provide certain mechanical strength, and in some cases deliver antibiotics to prevent infections. Until now, none of the existing wound dressing products can meet all these requirements. To design a wound dressing with as many of the aforementioned features as possible, in this study, we attempted to prepare ciprofloxacin (CIP), an antibiotic, loaded electrospun hydrophobic poly (lactic‐co‐glycolic acid) (PLGA) fibrous mats modified with hydrophilic sodium alginate (ALG) microparticles. The results showed that ALG could improve the wettability, water absorption capacity, and enhance the release rate of ciprofloxacin from the PLGA fibrous mats. In addition, the addition of ALG reduced the stiffness of PLGA fibrous mats for better protection of the injured area as indicated by the Young’s modulus. Moreover, the burst release of CIP resulted from the addition of ALG seemed to provide an improved antimicrobial effect to the PLGA mats. This study demonstrated the potential of combining hydrophilic and hydrophobic polymers to design the desired wound dressings via the electrospinning process.

Chemometrics for Analytical Data Mining in Separation Process Design for Recovery of Artemisinin from Artemisia annua

The separation process for recovery of natural products from plants very often employs multiple separation techniques, and key to the success of such processes is to find the synergy between different separation techniques. Molecular level understanding of process streams is highly required in order to determine the synergy between unit operations, which can be attained through analysis of process streams using advanced process analyzers such as high performance liquid chromatography (HPLC), liquid chromatography–mass spectrometry (LC-MS), etc. Very often use of such process analyzers generates an enormous amount of data making it difficult to extract useful information. Therefore, application of chemometrics for extracting process information from analytical data of process streams is demonstrated in this work. The multivariate data analysis technique PARAFAC is used to extract chemical information such as number of impurities, their relative concentrations, and finally their identification from rather complex analytical chromatograms of flash column chromatography (flash CC) fractions during purification of artemisinin from the crude extract of Artemisia annua. Crude extract of A. annua leaves obtained from dichloromethane is used in this work. Prior to the application of PARAFAC, the data set is preprocessed to remove baseline drift and peak misalignment caused by retention time shifts due to matrix effects. The process information extracted from analytical chromatograms by using the PARAFAC technique indicated the presence of impurities ranging from coumarins, polyacetylenes, and flavonoids to artemisinin related compounds in the flash CC fractions.