Novel Salt-Cocrystals of Berberine Hydrochloride with Aliphatic Dicarboxylic Acids: Odd-Even Alternation in Physicochemical Properties

Highly Soluble Dacarbazine Multicomponent Crystals Less Prone to Photodegradation

Dacarbazine (DTIC) is a widely prescribed oncolytic agent to treat advanced malignant melanomas. Nevertheless, the drug is known for exhibiting low and pH-dependent solubility, in addition to being photosensitive. These features imply the formation of the inactive photodegradation product 2-azahypoxanthine (2-AZA) during pharmaceutical manufacturing and even drug administration. We have focused on developing novel DTIC salt/cocrystal forms with enhanced solubility and dissolution behaviors to overcome or minimize this undesirable biopharmaceutical profile. By cocrystallization techniques, two salts, two cocrystals, and one salt-cocrystal have been successfully prepared through reactions with aliphatic carboxylic acids. A detailed structural study of these new multicomponent crystals was conducted using X-ray diffraction (SCXRD, PXRD), spectroscopic (FT-IR and 1H NMR), and thermal (TG and DSC) analyses. Most DTIC crystal forms reported display substantial enhancements in solubility (up to 19-fold), with faster intrinsic dissolution rates (from 1.3 to 22-fold), contributing positively to reducing the photodegradation of DTIC in solution. These findings reinforce the potential of these new solid forms to enhance the limited DTIC biopharmaceutical profile.

Modulating Pharmaceutical Properties of Berberine Chloride through Cocrystallization with Benzendiol Isomers

PURPOSE

To synthesize and characterize new cocrystals of berberine chloride (BCl) for potential pharmaceutical tablet formulation.

METHODS

Solutions of BCl with each of three selected cocrystal formers, catechol (CAT), resorcinol (RES), and hydroquinone (HYQ) were slowly evaporated at room temperature to obtain crystals. Crystal structures were solved using single crystal X-ray diffraction. Bulk powders were characterized by powder X-ray diffraction, thermogravimetric-differential scanning calorimetry, FTIR, dynamic moisture sorption, and dissolution (both intrinsic and powder).

RESULTS

Single crystal structures confirmed the formation of cocrystals with all three coformers, which revealed various intermolecular interactions that stabilized crystal lattices, including O-H···Cl- hydrogen bonds. All three cocrystals exhibited better stability against high humidity (up to 95% relative humidity) at 25 ℃ and higher intrinsic and powder dissolution rates than BCl.

CONCLUSION

The enhanced pharmaceutical properties of all three cocrystals, as compared to BCl, further contribute to the existing evidence that confirms the beneficial role of cocrystallization in facilitating drug development. These new cocrystals expand the structure landscape of BCl solid forms, which is important for future analysis to establish a reliable relationship between crystal structure and pharmaceutical properties.

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.

Development of Gelled-Oil Nanoparticles for the Encapsulation and Release of Berberine

In this study, a new drug carrier based on gelled-oil nanoparticles (GNPs) was designed and synthesized for the encapsulation and release of the model hydrophobic drug, berberine chloride (BCl). Two compositions with different oil phases were examined, sesame oil (SO) and cinnamaldehyde (Cin), which were emulsified with water, stabilized with Tween 80 (Tw80), and gelled using an N-alkylated primary oxalamide low-molecular-weight gelator (LMWG) to give stable dispersions of GNPs between 100 and 200 nm in size. The GNP formulation with Cin was significantly favored over SO due to (1) lower gel melting temperatures, (2) higher gel mechanical strength, and (3) significantly higher solubility, encapsulation efficiency, and loading of BCl. Also, the solubility and loading of BCl in Cin were significantly increased (at least 7-fold) with the addition of cinnamic acid. In vitro release studies showed that the release of BCl from the GNPs was independent of gelator concentration and lower than that for BCl solution and the corresponding nanoemulsion (no LWMG). Also, cell internalization studies suggested that the N-alkylated primary oxalamide LMWG did not interfere with the internalization efficiency of BCl into mouse mast cells. Altogether, this work demonstrates the potential use of these new GNP formulations for biomedical studies involving the encapsulation of drugs and nutraceuticals and their controlled release.

Novel multi-component crystals of berberine with improved pharmaceutical properties

As an extremely popular natural product, berberine (BER) is mainly used for gastroenteritis and diarrhoea caused by bacteria. Research has also revealed the potent and extensive pharmacological properties of BER including its anti-arrhythmic, anti-tumour, anti-inflammatory and hypoglycemic activities and so on; therefore, BER is a promising drug for further development. However, its commercial form with hydrochloride exhibits poor stability and solubility, which are detrimental to its clinical therapeutic effects. For these purposes, the salt form was regulated via the reactive crystallization of 8-hydroxy-7,8-dihydroberberine (8H-HBER) with five pharmaceutically suitable organic acids including malonic acid (MA), L-tartaric acid (LTA), D-tartaric acid (DTA), DL-tartaric acid (DLTA) and citric acid (CA), resulting in the six novel solid forms 1BER-1LTA-1W, 1BER-1DTA-1W, 1BER-1DLTA and 2BER-2CA as well as two rare multi-stoichiometric solid forms 1BER-1MA and 1BER-2MA-2W. The preparation of the multi-stoichiometric products was greatly influenced by both the crystallization solvent type and the molar ratio of reactants. The structures of these multi-component solid forms were determined using single-crystal X-ray diffraction and further characterized by powder X-ray diffraction, thermal analysis and Fourier transform infrared spectroscopy. Stability experiments showed that all samples prepared had superior physical stability under high temperature and high humidity. Furthermore, dissolution experiments demonstrated that the maximum apparent solubilities (MAS) of all the products were significantly improved compared with the commercial form of BER in dilute hydrochloric solution (pH = 1.2). In particular, the MAS of 1BER-1MA in dilute hydrochloric solution is as high as 34 times that of the commercial form. In addition, it is preliminarily confirmed that the MAS of the samples prepared in pure water and dilute hydrochloric solution is primarily influenced by a combination of factors including the packing index, intermolecular interactions, affinity of the counter-ion to the solvent, the molar ratio of the drug to counter-ion in the product and the common ion effect. These novel solids are potential candidates for BER solid forms with improved oral dosage design and may prompt further development.

Formulation Strategies to Improve the Stability and Handling of Oral Solid Dosage Forms of Highly Hygroscopic Pharmaceuticals and Nutraceuticals

Highly hygroscopic pharmaceutical and nutraceutical solids are prone to significant changes in their physicochemical properties due to chemical degradation and/or solid-state transition, resulting in adverse effects on their therapeutic performances and shelf life. Moisture absorption also leads to excessive wetting of the solids, causing their difficult handling during manufacturing. In this review, four formulation strategies that have been employed to tackle hygroscopicity issues in oral solid dosage forms of pharmaceuticals/nutraceuticals were discussed. The four strategies are (1) film coating, (2) encapsulation by spray drying or coacervation, (3) co-processing with excipients, and (4) crystal engineering by co-crystallization. Film coating and encapsulation work by acting as barriers between the hygroscopic active ingredients in the core and the environment, whereas co-processing with excipients works mainly by adding excipients that deflect moisture away from the active ingredients. Co-crystallization works by altering the crystal packing arrangements by introducing stabilizing co-formers. For hygroscopic pharmaceuticals, coating and co-crystallization are the most commonly employed strategies, whereas coating and encapsulation are popular for hygroscopic nutraceuticals (e.g., medicinal herbs, protein hydrolysates). Encapsulation is rarely applied on hygroscopic pharmaceuticals, just as co-crystallization is rarely used for hygroscopic nutraceuticals. Therefore, there is potential for improved hygroscopicity reduction by exploring beyond the traditionally used strategy.

Complexation with aromatic dicarboxylic acids expands the solid-state landscape of berberine

Two novel salt cocrystals of berberine chloride (BCl) with 4-aminobenzoic acid (BCl-4ABA) and 4-hydroxybenzoic acid (BCl-4HBA) and one new berberine salt with 2,6-dihydroxybenzoic acid (B)⁺(26DHBA)^- were prepared and characterized. The chloride anions form N-H···Cl^- hydrogen bonds in BCl-4ABA and O-H···Cl^- hydrogen bonds in BCl-4HBA. In (B)⁺(26DHBA)^-, the ionic interactions between 26DHBA^- and quaternary ammonium cation of berberine contribute to a stronger crystal lattice and a higher melting point. All three new crystal forms exhibit a lower hygroscopicity at 25 ℃ than BCl, which is the crystal form used in the commercial tablets. Compared to BCl, the dissolution rates of BCl-4ABA and BCl-4HBA in water are higher but that of (B)⁺(26DHBA)^- is lower. Among the three crystal forms, the form with a higher melting point also exhibits a lower dissolution rate, which is explained by the stronger intermolecular interactions in these crystals.

Assessment of Computational Tools for Predicting Supramolecular Synthons

The ability to predict the most likely supramolecular synthons in a crystalline solid is a valuable starting point for subsequently predicting the full crystal structure of a molecule with multiple competing molecular recognition sites. Energy and informatics-based prediction models based on molecular electrostatic potentials (MEPs), hydrogen-bond energies (HBE), hydrogen-bond propensity (HBP), and hydrogen-bond coordination (HBC) were applied to the crystal structures of twelve pyrazole-based molecules. HBE, the most successful method, correctly predicted 100% of the experimentally observed primary intermolecular-interactions, followed by HBP (87.5%), and HBC = MEPs (62.5%). A further HBC analysis suggested a risk of synthon crossover and synthon polymorphism in molecules with multiple binding sites. These easy-to-use models (based on just 2-D chemical structure) can offer a valuable risk assessment of potential formulation challenges.