Terahertz and Raman Spectroscopic Investigation of Monohydrate Cocrystal of Antitubercular Isoniazid with Protocatechuic Acid

Vibrational spectroscopic detection and analysis of salicylic acid and aspirin binary cocrystal

Salicylic acid is a raw material for preparing aspirin and holds an important position in medical history. Studying the crystallization of these two drugs is of great significance in improving their dissolution rate, bioavailability, and physical stability. Although various techniques have been used for structural characterization, there is still a lack of information on the collective vibrational behavior of aspirin and salicylic acid eutectic compounds. Firstly, two starting materials (salicylic acid and aspirin) were ground in a 1:1 M ratio to prepare eutectic compounds. The eutectic composition was studied using vibrational spectroscopy techniques, such as X-ray powder diffusion (XRPD), terahertz time-domain spectroscopy (THz-TDS), and Raman spectroscopy. Additionally, the structure of the aspirin and salicylic acid eutectic was simulated and optimized using density functional theory. It was found that the eutectic type II was the most consistent with the experiment, and the corresponding vibration modes of each peak were provided. These results offer a unique method for characterizing the structural composition of eutectic crystals, which can be utilized to enhance the physical and chemical properties, as well as the pharmacological activity, of specific drugs at the molecular level.

Investigation into polymorphism within ethenzamide-ethylmalonic acid cocrystal using Raman and terahertz vibrational spectroscopy

Two cocrystal polymorphs of ethenzamide (ETZ) and ethylmalonic acid (EMA) were synthesized by solvent evaporation. Crystal structure analysis revealed that the main amide - carboxyl heterosynthon in ETZ-EMA cocrystal Form I and Form II are the same, but the crystal structure of these two polymorphs are different. Terahertz (THz) and Raman vibrational spectroscopy were used to characterize ETZ, EMA, ETZ-EMA cocrystal polymorph Form I and Form II respectively. The experimental results showed that ETZ, EMA, ETZ-EMA cocrystal Form I and ETZ-EMA cocrystal Form II exhibited completely different characteristic peaks. Both THz and Raman vibrational spectroscopy can be used to distinguish ETZ-EMA cocrystal Form I from Form II. Furthermore, the investigation of phase transition induced by temperature and solid-state grinding was also performed. In the temperature phase transition experiments, when the powder sample was heated to a temperature range of 80-82 °C, the metastable ETZ-EMA cocrystal Form I transformed into the more stable ETZ-EMA cocrystal Form II. Solid-state grinding analysis revealed that the results of the ETZ-EMA cocrystal polymorph synthesis in grinding experiments depended on the polarity of the solvents used. Grinding without solvent or with high polarity solvents tended to result in the stable ETZ-EMA cocrystal Form II. Moreover, the metastable ETZ-EMA cocrystal Form I would transform into Form II after further grinding process. These results demonstrate that THz and Raman vibrational spectroscopy have high sensitivity and accuracy in the detection of both cocrystal synthesis and cocrystal polymorph phase transitions.

Novel co-crystal of 3-methylcinnamic acid with berberine (1:1): synthesis, characterization, and intestinal absorption property

OBJECTIVE

To synthesis a novel 'Pharmaceutical Cocrystal' of berberine (BBR) with coformer 3-methylcinnamic acid (3MCA) for increasing its solubility and intestinal absorption property.

SIGNIFICANCE

BBR-HCl has poor liposolubility, difficulty in penetrating the cell membrane and absorption in the gastrointestinal tract, low bioavailability, and limited clinical application. A new cocrystal is formed by the interaction between 3-MCA and BBR through molecular interaction, which improves the physicochemical properties, intestinal absorption property, and hygroscopicity.

METHODS

The solvent evaporation method was used to synthesize BCR-3MCA cocrystal. The physicochemical properties of the crystals were confirmed by different spectral techniques, i.e. by X-ray diffraction (PXRD, SXRD), thermogravimetry and differential thermal analysis (DSC, TGA), and scanning electron microscopy (SEM). Hygroscopicity of the cocrystal was evaluated by dynamic water vapor sorption (DVS). The intestinal absorption property was evaluated by the Ussing chamber system.

RESULTS

BBR and 3MCA can be directly self-assembled into uniform co-crystal by hydrogen bonds and π-π stacking interactions. Compared with BBR-HCl, the solubility of BBR-3MCA cocrystal in polar solvents of water, methanol, ethanol, and isopropanol increased by 13.9, 1.5, 4.7, and 15.8 times, respectively. The apparent absorption and the absorption rate constants were increased by 7.7 and 5.6 times, respectively. Surprisingly, BBR-3MCA co-crystal almost had no hygroscopicity.

CONCLUSION

The absolute molecular structure of the co-crystal was further confirmed by single crystal X-ray diffraction. The hydrogen bonds drove the formation of X-like one-dimensional unit. Compared to the BBR-HCl, BBR-3MCA cocrystal displayed superior dissolution and solubility performance, improved physical-chemical properties and significantly improved intestinal absorption.

In Situ Cocrystallization via Spray Drying with Polymer as a Strategy to Prevent Cocrystal Dissociation

The aim of the present study was to investigate how different polymers affect the dissociation of cocrystals prepared by co-spray-drying active pharmaceutical ingredient (API), coformer, and polymer. Diclofenac acid-l-proline cocrystal (DPCC) was selected in this study as a model cocrystal due to its previously reported poor physical stability in a high-humidity environment. Polymers investigated include polyvinylpyrrolidone (PVP), poly(1-vinylpyrrolidone-co-vinyl acetate) (PVPVA), hydroxypropyl methyl cellulose, hydroxypropylmethylcellulose acetate succinate, ethyl cellulose, and Eudragit L-100. Terahertz Raman spectroscopy (THz Raman) and powder X-ray diffraction (PXRD) were used to monitor the cocrystal dissociation rate in a high-humidity environment. A Raman probe was used in situ to monitor the extent of the dissociation of DPCC and DPCC in crystalline solid dispersions (CSDs) with polymer when exposed to pH 6.8 phosphate buffer and water. The solubility of DPCC and solid dispersions of DPCC in pH 6.8 phosphate buffer and water was also measured. The dissociation of DPCC was water-mediated, and more than 60% of DPCC dissociated in 18 h at 40 °C and 95% RH. Interestingly, the physical stability of the cocrystal was effectively improved by producing CSDs with polymers. The inclusion of just 1 wt % polymer in a CSD with DPCC protected the cocrystal from dissociation over 18 h under the same conditions. Furthermore, the CSD with PVPVA was still partially stable, and the CSD with PVP was stable (undissociated) after 7 days. The superior stability of DPCC in CSDs with PVP and PVPVA was also demonstrated when systems were exposed to water or pH 6.8 phosphate buffer and resulted in higher dynamic solubility of the CSDs compared to DPCC alone. The improvement in physical stability of the cocrystal in CSDs was thought to be due to an efficient mixing between polymer and cocrystal at the molecular level provided by spray drying and in situ gelling of polymer. It is hypothesized that polymer chains could undergo gelling in situ and form a physical barrier, preventing cocrystal interaction with water, which contributes to slowing down the water-mediated dissociation.

Vibrational spectroscopic detection and analysis of isoniazid-nicotinamide-succinic acid ternary cocrystal

In this paper, binary and ternary cocrystals in the ternary cocrystal system of isoniazid-nicotinamide-succinic acid were prepared by solvent evaporation and grinding methods. All of them were characterized by terahertz time-domain spectroscopy (THz-TDS), confirming that the cocrystals could be obtained by the above two methods. In addition, to investigate the formation of hydrogen bonds and their influence in cocrystal, several possible forms of hydrogen bond in cocrystal were simulated by density functional theory (DFT). The simulated result was in good agreement with the experimental result, indicating that the hydrogen bonds in cocrystal were the carboxyl groups on both side of succinic acid forming a pyridine N-carboxylic acid heterosynthon with pyridine N of isoniazid or nicotinamide respectively. Meanwhile, the vibrational modes of the cocrystal were analyzed to investigate the effect of hydrogen bond to the molecules. To further understand the formation process of ternary cocrystal in this system, Raman spectroscopy was used to analyze the cocrystal samples with different time of grinding. Process information of cocrystal formation were obtained by analyzing the changes of the characteristic peaks in the corresponding Raman spectra. These results provide a wealth of information and a unique approach to the analysis of both structures and intermolecular interactions shown within ternary cocrystal.

Terahertz Spectroscopic Analysis of Lactose in Infant Formula: Implications for Detection and Quantification

Lactose plays a significant role in daily lives as a constituent of various food and pharmaceutical products. Yet, lactose intolerance conditions demand low-lactose and lactose-free products in the market. These increasing nutritional claims and labels on food products entail simple and reliable methods of analysis that can be used for meeting quality standards, nutritional claims and legal requirements. In this study, terahertz time-domain spectroscopy (THz-TDS) was employed to analyse α-lactose monohydrate qualitatively and quantitatively in food products. Both absorption spectra and absorption coefficient spectra were investigated for their prediction performance. Regression models for lactose quantification using peak area and height of the absorption peaks 0.53 and 1.37 THz were developed and assessed in infant formula samples. Satisfactory prediction results were achieved in ideal conditions with pure standards, but not in all predictions of infant formula samples. Reasons and further implications are discussed.

Multicomponent crystal compromising dasatinib and selected co-crystals formers: a patent evaluation of EP2861589B1

Cocrystallization has gained significant prominence in pharmaceutical product development because of the enhancement of physical, chemical and pharmacological properties of active pharmaceutical ingredients, such as stability, solubility, dissolution rate, taste, hygroscopicity, mechanical property, bioavailability, permeability and therapeutic activity. Traditionally, co-crystals can be prepared by a grinding, solvent evaporation and slurry method. However, sophisticated methods such as spa drying, hot-melt extrusion, supercritical fluid and laser irradiation are also reported to be used for producing co-crystals. The selected patent describes the development of multicomponent crystals of dasatinib, with an aim to enhance the aqueous solubility of a selected drug. However issues surrounding the toxicity, stability, large scale manufacture, in vivo performance in human beings and regulations require adequate addressal prior to exploring the commercial viability of pharmaceutical co-crystals.