Thermoanalytical and spectroscopic characterisation of solid-state retinoic acid

Solubility and Thermodynamic Analysis of Isotretinoin in Different (DMSO + Water) Mixtures

The solubility and solution thermodynamics of isotretinoin (ITN) (3) in numerous {dimethyl sulfoxide (DMSO) (1) + water (H2O) (2)} combinations were studied at 298.2-318.2 K under fixed atmospheric pressure of 101.1 kPa. A shake flask methodology was used to determine ITN solubility, and correlations were made using the "van't Hoff, Apelblat, Buchowski-Ksiazczak λh, Yalkowsky-Roseman, Jouyban-Acree, and Jouyban-Acree-van't Hoff models". In mixtures of {(DMSO (1) + H2O (2)}, the solubility of ITN in mole fractions was enhanced with the temperature and DMSO mass fraction. The mole fraction solubility of ITN was highest in neat DMSO (1.02 × 10-1 at 318.2 K) and lowest in pure H2O (3.14 × 10-7 at 298.2 K). The output of computational models revealed good relationships between the solubility data from the experiments. The dissolution of ITN was "endothermic and entropy-driven" in all of the {(DMSO (1) + H2O (2)} mixtures examined, according to the positive values of measured thermodynamic parameters. Enthalpy was discovered to be the driving force behind ITN solvation in {(DMSO (1) + H2O (2)} combinations. ITN-DMSO displayed the highest molecular interactions when compared to ITN-H2O. The outcomes of this study suggest that DMSO has a great potential for solubilizing ITN in H2O.

Solubilization and Thermodynamic Analysis of Isotretinoin in Eleven Different Green Solvents at Different Temperatures

The solubilization and thermodynamic analysis of isotretinoin (ITN) in eleven distinct green solvents, such as water, methyl alcohol (MeOH), ethyl alcohol (EtOH), 1-butyl alcohol (1-BuOH), 2-butyl alcohol (2-BuOH), ethane-1,2-diol (EG), propane-1,2-diol (PG), polyethylene glycol-400 (PEG-400), ethyl acetate (EA), Transcutol-HP (THP), and dimethyl sulfoxide (DMSO) was studied at several temperatures and a fixed atmospheric pressure. The equilibrium approach was used to measure the solubility of ITN, and the Apelblat, van’t Hoff, and Buchowski−Ksiazczak λh models were used to correlate the results. The overall uncertainties were less than 5.0% for all the models examined. The highest ITN mole fraction solubility was achieved as 1.01 × 10−1 in DMSO at 318.2 K; however, the least was achieved as 3.16 × 10−7 in water at 298.2 K. ITN solubility was found to be enhanced with an increase in temperature and the order in which it was soluble in several green solvents at 318.2 K was as follows: DMSO (1.01 × 10−1) > EA (1.73 × 10−2) > PEG-400 (1.66 × 10−2) > THP (1.59 × 10−2) > 2-BuOH (6.32 × 10−3) > 1-BuOH (5.88 × 10−3) > PG (4.83 × 10−3) > EtOH (3.51 × 10−3) > EG (3.49 × 10−3) > MeOH (2.10 × 10−3) > water (1.38 × 10−6). ITN−DMSO showed the strongest solute−solvent interactions when compared to the other ITN and green solvent combinations. According to thermodynamic studies, ITN dissolution was endothermic and entropy-driven in all of the green solvents tested. The obtained outcomes suggested that DMSO appears to be the best green solvent for ITN solubilization.

Zein/Phospholipid Composite Nanoparticles for Successful Delivery of Gallic Acid into aHSCs: Influence of Size, Surface Charge, and Vitamin A Coupling

PURPOSE

Zein/phospholipid composite nanoparticles (CNPs) were developed as a delivery platform for gallic acid (GA), a polyphenolic compound with reported preclinical antifibrotic activities. However, the therapeutic applicability of GA is hampered owing to its low bioavailability and rapid clearance. Accordingly, we developed GA-loaded CNPs. The effect of their size, surface charge and targeting strategies was investigated and optimized, with the aim of enhancing their ability to deliver GA to the activated hepatic stellate cells (aHSCs) in order to suppress hepatic fibrosis progression.

METHODS

Different CNP systems were prepared and characterized with regard to their particle size, zeta potential, and GA entrapment efficiency (EE%). Also, they were statistically optimized via response surface methodology. The optimized systems were investigated with regard to their in vitro GA release, in vitro efficacy on aHSCs, and in vivo biodistribution in healthy rats.

RESULTS

The GA-loaded cationic CNPs coupled with vitamin A (GA-CACNP/VA; 192 nm) showed high GA EE% (60% w/w), highest cellular internalization via active targeting, and more selective hepatic distribution, relative to free GA solution, GA-loaded anionic, and GA-loaded cationic systems. Furthermore, GA-CACNP/VA markedly triggered the apoptosis of aHSCs, repressed collagen deposition, and inhibited HSCs' activation to a lesser extent.

CONCLUSION

The GA-CACNP/VA was shown to be a promising candidate for specific and controlled delivery of GA to aHSCs, which may provide an effective antifibrotic therapeutic approach.

Polymeric micelles of PEG-PE as carriers of all-trans retinoic acid for stability improvement

The topical application of all-trans retinoic acid (ATRA) is an effective treatment for several skin disorders, including photo-aging. Unfortunately, ATRA is susceptible to light, heat, and oxidizing agents. Thus, this study aimed to investigate the ability of polymeric micelles prepared from polyethylene glycol conjugated phosphatidylethanolamine (PEG-PE) to stabilize ATRA under various storage conditions. ATRA entrapped in polymeric micelles with various PEG and PE structures was prepared. The critical micelle concentrations were 97-243 μM, depending on the structures of the PEG and PE molecules. All of the micelles had particle diameters of 6-20 nm and neutral charges. The highest entrapment efficiency (82.7%) of the tested micelles was exhibited by ATRA in PEG with a molecular weight of 750 Da conjugated to dipalmitoyl phosphatidylethanolamine (PEG(750)-DPPE) micelles. The PEG(750)-DPPE micelle could significantly retard ATRA oxidation compared to ATRA in 75% methanol/HBS solution. Up to 87% of ATRA remained in the PEG(750)-DPPE micelle solution after storage in ambient air for 28 days. This result suggests that PEG(750)-DPPE micelle can improve ATRA stability. Therefore, ATRA in PEG(750)-DPPE micelle is an interesting alternative structure for the development of cosmeceutical formulations.

Desenvolvimento e validação de método analítico em CLAE-UV para a quantificação de ácido retinóico em microcápsulas de alginato e quitosana

O ácido retinóico (AR) tem sido utilizado para o tratamento de acne severa, rugas, estrias e celulite, no entanto, provoca irritação na pele e sofre rápida degradação quando exposto à luz e ao calor. Métodos analíticos rápidos para quantificação do AR são, portanto, necessários para ensaios de cinética de liberação in vitro. Nesse contexto, o objetivo deste trabalho foi desenvolver e validar um método rápido e sensível para o doseamento do AR em microcápsulas de alginato/quitosana contendo óleo de babaçu dispersas em gel natrosol® por cromatografia líquida de alta eficiência associada à espectroscopia UV e aplicá-lo na avaliação do perfil de liberação in vitro dessas formulações. As análises foram realizadas em modo isocrático utilizando coluna C18 de fase reversa 150 x 4,6 mm (5 μm) com detecção a 350 nm. A fase móvel foi constituída de metanol e ácido acético 1% (85:15 v/v) com vazão de 1,8 mL/minuto. A faixa de linearidade do método foi de 0,5 a 60 μg/mL (r² = 0,999). O método validado mostrou-se sensível, específico, exato, preciso, de baixo custo e o tempo de retenção do AR foi de 5,8 ± 0,4 minutos sendo, desta forma, mais rápido do que os relatados na literatura.

Physical Characterization of Anhydrous and Hydrous Forms of the Hydrochloride Salt of BVT.5182 A Novel 5-HT6Receptor Antagonist

The physicochemical properties of 1-benzenesulfonyl-4-(piperazin-1-yl)-indole hydrochloride, a novel 5-HT(6) receptor antagonist for the treatment of obesity were characterized. Two solid state forms were identified at ambient conditions (23 degrees C): an anhydrate form (1) and a hydrate form (2), with 1.5 moles of H(2)O. The latter easily dehydrates and rehydrates without affecting the crystal morphology. Investigations of the propensity for interconversion between the two forms reveal that a) conversion of 2-->1 takes place above 145 degrees C and that b) conversion of 1-->2 only occurs after crystallization from supersaturated aqueous solutions at a water activity >or=0.94 or in the presence of comparable amounts of crystals of 2 in water at ambient conditions. However, in an equimolar suspension of 1 and 2 at 37 degrees C no phase transformation was observed. Thus, the difference in chemical potential between the two forms is small. Form 1 was shown to have overall favorable solid state properties and, hence, considered the preferred form for continued pharmaceutical development. The characterization was performed by means of light microscopy, scanning electron microscopy, powder X-ray diffraction, FTIR/NIR-spectroscopy, differential scanning calorimetry, hot stage microscopy, thermogravimetry, dynamic vapor sorption, Karl Fischer water content determination, phase stability studies of suspensions, solubility, and intrinsic dissolution rate measurements.

Preparation of All-Trans Retinoic Acid Nanosuspensions Using a Modified Precipitation Method

All-Trans Retinoic Acid (ATRA) nanosuspensions were prepared with a modified precipitation method. The ATRA solution in acetone was injected into pure water by an air compressor under the action of ultrasonication. Photon correlation spectroscopy results showed that the mean particle size of ATRA nanoparticles in nanosuspensions reduced from 337 nm to 155 nm as the injection velocity increased and the polydispersity index was 0.45-0.50. The morphology of ATRA nanoparticles varied with the different concentration of ATRA solution in acetone. ATRA nanoparticles showed an amorphous state and stable in 6 months. It could be concluded that this modified precipitation method could produce stable and controllable ATRA nanosuspension to a certain extent, thus benefit for higher saturation solubility.

Analysis of Quil A–phospholipid mixtures using drift spectroscopy

The aim of this study was to investigate molecular interactions between Quil A and phosphatidylcholine in the solid state using diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS). Analysis of the interactions was characterized on the different regions of phosphatidylcholine: hydrophobic chain, interfacial and headgroup regions. The spectra of the hydrocarbon region of phosphatidylcholine alone compared to that for the binary mixture of Quil A and phosphatidylcholine were similar. These findings suggest that Quil A did not cause conformational disorder of the fatty acyl chains of the phospholipid. In contrast, a shift in the wavenumber of the choline group and a broad band in this moiety indicate a modification of the phospholipid in the headgroup region due to interaction between Quil A and phosphatidylcholine. These results suggest possibly ionic interactions between the negatively charged glucuronic acid moiety of the Quil A molecule with the positively charged choline group. The findings could also be the result of conformational changes in the choline group because of the intercalation of sugar moieties in Quil A between the choline and phosphate groups due to hydrogen bonding. Shift of wavenumbers to lower values on the carbonyl group was observed suggesting hydrogen bonding between Quil A and phosphatidylcholine. The difference in degrees of wavenumber shift (choline>phosphate>carbonyl group) and observed broad bands indicated that Quil A preferentially interacted with phosphatidylcholine on the hydrophilic headgroup. Cholesterol influenced such interactions at relatively high concentration (60%, w/w).

Study of retinoic acid polymorphism

Some authors recently hypothesized the existence of a new retinoic acid (RA) phase in addition to the two already known polymorphs. We investigated RA polymorphism and our results exclude the presence of new modifications and refine the properties of the known forms. By comparison of simulated and acquired X-Ray Powder Diffraction (XRPD) it was possible to identify only the known monoclinic (I) and the triclinic (II) modifications; the same were also characterized by DSC, IR, and Raman spectroscopy. A solubility study associated to DSC allowed establishing an enantiotropic relationship between the two forms, with form II being less stable (DeltaGII/I=0.71 kJ/mol at 37 degrees C) below the transition temperature (136.6 degrees C; DeltaH=3.2 kJ/mol). The intrinsic dissolution rate (IDR) (I=61 microg/cm2xmin-1; II=125 microg/cm2xmin-1) confirmed this energetic relationship. The kinetics of solid transition I-->II was examined and its activation energy estimated (356 kJ/mol). The attempts to produce new phases allowed the development of methods to obtain the two polymorphs with high chemical and polymorphic purity. A validated DSC method is presented that enables detection of the presence of form I at a level of 1% (w/w) when in mixture with form II.

Development of a gas chromatography method for the determination of isotretinoin and its degradation products in pharmaceuticals

This paper describes the development of a gas chromatography (GC) method used for the assay of isotretinoin in its isolated form and in pharmaceutical formulations. Isotretinoin soft and hard gelatin capsules were prepared with various excipients. The performance of the proposed gas chromatography method was compared to that of traditional high performance liquid chromatography (HPLC) systems for this substance, and the GC parameters were established based on several preliminary tests, including thermal analysis of isotretinoin. Results showed that gas chromatography-flame ionization detector (GC-FID) exhibited a separation efficiency superior to that of HPLC, particularly for separating isotretinoin degradation products. This method was proven to be effectively applicable to stability evaluation assays of isotretinoin and isotretinoin based pharmaceuticals.