Solubility and dissolution studies of tibolone polymorphs

Formulation of water-soluble Buddleja globosa Hope extracts and characterization of their antimicrobial properties against Pseudomonas aeruginosa

Buddleja globosa Hope (BG) extracts are traditionally used to treat skin and gastric ulcers due to their healing properties. Non-aqueous solvents such as ethanol and DMSO are usually used to extract naturally occurring compounds. However, the cytotoxicity of these solvents and the low water solubility of the extracted compounds can hinder their biomedical applications. To overcome the limited solubility of the BG extracts, we aimed to enhance the solubility by processing a standardized hydroalcoholic extract (BG-126) through spray drying (SD), with and without two solubility enhancers. Spray-dried BG (BG-SD) extracts and spray-dried BG extracts plus polyvinylpyrrolidone (BG-SD PVP) and Soluplus® (BG-SD SP) were developed starting from BG-126 (containing 53% ethanol). These four formulations were characterized by total phenolic content, water solubility at 25°C and 37°C, and antimicrobial properties against Pseudomonas aeruginosa. All the SD formulations presented a solubility that allowed them to reach maximum concentrations of 1,024 μg/ml catechin for BG-SD and 2,048 μg/ml catechin for BG-SD PVP and BG-SD SP for antimicrobial testing. BG-SD showed the highest antimicrobial potency with a minimum inhibitory concentration (MIC) of 512 μg/ml catechin, followed by BG-126 with a MIC of 1,024 μg/ml catechin and SP. BG-126 was also shown to inhibit biofilm formation, as well as the excipients PVP and SP. The spray-dried BG (BG-SD) extract represents a promising natural active component with enhanced antimicrobial properties against P. aeruginosa for further research and the development of novel phytopharmaceuticals.

Structural Polymorphism of Sorafenib Tosylate as a Key Factor in Its Solubility Differentiation

The presence of active pharmaceutical ingredients (APIs) in the forms of different polymorphic states can induce differences in their physicochemical properties. In the case of poorly soluble APIs, like the oncological drug sorafenib tosylate, small variations in solubility may result in large bioavailability differences. The control of its therapeutic dose is crucial from the effective pharmacotherapy point of view and the reduction of side effects. Therefore, this study aimed to assess the influence of sorafenib tosylate polymorphic forms on its solubility and, consequently, permeability, based on passive diffusion through membranes simulating the gastrointestinal tract (GIT) conditions. In the first part of the work, two crystalline forms of sorafenib tosylate were identified using the X-ray powder diffraction, FT-IR, and Raman spectroscopy. Subsequently, solubility studies were carried out. Both forms of sorafenib tosylate were insoluble in 0.1 N hydrochloric acid (HCl), in acetate buffer (pH 4.5), and in phosphate buffer (pH 6.8). Solubility (mg/mL) of form I and III of sorafenib tosylate in 0.1 N HCl + 1.0% SDS was 0.314 ± 0.006 and 1.103 ± 0.014, respectively, in acetate buffer pH 4.5 + 1.0% SDS it was 2.404 ± 0.012 and 2.355 ± 0.009, respectively, and in phosphate buffer pH 6.8 + 1.0% SDS it was 0.051 ± 0.005 and 1.805 ± 0.023, respectively. The permeability study was assessed using the parallel artificial membrane permeability assay (PAMPA) model. The apparent permeability coefficient (P_app—cm s⁻¹) of form I and III in pH 1.2 was 3.01 × 10⁻⁵ ± 4.14 × 10⁻⁷ and 3.15 × 10⁻⁵ ± 1.89 × 10⁻⁶, respectively, while in pH 6.8 it was 2.72 × 10⁻⁵ ± 1.56 × 10⁻⁶ and 2.81 × 10⁻⁵ ± 9.0 × 10⁻⁷, respectively. Changes in sorafenib tosylate concentrations were determined by chromatography using the high-performance liquid chromatography (HPLC)–DAD technique. As a result of the research on the structural polymorphism of sorafenib tosylate, its full spectral characteristics and the possibility of using FT-IR and Raman spectroscopy for the study of polymorphic varieties were determined for the first time, and the HPLC method was developed, which is appropriate for the assessment of sorafenib solubility in various media. The consequences of various physicochemical properties resulting from differences in the solubility of sorafenib tosylate polymorphs are important for pre-formulation and formulation studies conducted with its participation and for the safety of oncological sorafenib therapy.

Understanding Crystal Cleavability and Physical Properties of Crystal Surfaces Using in Silico Simulation

In the drug formulation process, compound dissolution rate and wettability may be improved by grinding. However, there is no method to understand the effects of the wettability of the crystal facets of the ground product. Here, acetylsalicylic acid (ASA) was used to evaluate the changes in crystal morphology and dissolution rate by jet milling using powder X-ray diffraction and in silico simulation. Several cleavage facets were observed in cube crystals, and the (0 0 2) facet was observed in plate crystals. Furthermore, the dissolution rate of the ground samples per unit area decreased with the cleavage of the (1 0 0) and (0 0 2) facets. The polar surface energy of the ground sample decreased with increasing grinding pressure. The simulation results showed that the absolute attachment energy of the (1 0 0) and (0 0 2) facets was lower than that of the other crystal facets. Moreover, atoms with low polarity were present on the crystal surface of (0 0 2). The wettability and dissolution rate of the (0 0 2) facet were worse than those of the (1 0 0) facet. It was suggested that the dissolution rate of the ground sample was affected by the wettability of the crystal facet caused by the cleavage. The cleavability and wettability may be understood by simulation.