A new bioactive cocrystal of coumarin-3-carboxylic acid and thiourea: detailed structural features and biological activity studies

Cocrystallization is a phenomenon widely used to enhance the biological and physicochemical properties of active pharmaceutical ingredients (APIs). The present study deals with the synthesis of a cocrystal of coumarin-3-carboxylic acid (2-oxochromene-3-carboxylic acid, C₁₀H₆O₄), a synthetic analogue of the naturally occurring antioxidant coumarin, with thiourea (CH₄N₂S) using the neat grinding method. The purity and homogeneity of the coumarin-3-carboxylic acid-thiourea (1/1) cocrystal was confirmed by single-crystal X-ray diffraction, FT-IR analysis and thermal stability studies based on differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Detailed geometry analysis via density functional theory (DFT) demonstrated that the 1:1 cocrystal stoichiometry is sustained by N-H...O hydrogen bonding between the amine (-NH₂) groups of thiourea and the carbonyl group of coumarin. The synthesized cocrystal exhibited potent antioxidant activity (IC₅₀ = 127.9 ± 5.95 µM) in a DPPH radical scavenger assay in vitro in comparison with the standard N-acetyl-L-cysteine (IC₅₀ = 111.6 ± 2.4 µM). The promising results of the present study highlight the significance of cocrystallization as a crystal engineering tool to improve the efficacy of pharmaceutical ingredients.

Sustainable solid form screening: mechanochemical control over nucleobase hydrogen-bonded organic framework polymorphism

The choice is yours! Liquid-assisted grinding can be used to control HOF polymorphism.

Mechanochemistry in Portugal-A Step towards Sustainable Chemical Synthesis

In Portugal, publications with mechanochemical methods date back to 2009, with the report on mechanochemical strategies for the synthesis of metallopharmaceuticals. Since then, mechanochemical applications have grown in Portugal, spanning several fields, mainly crystal engineering and supramolecular chemistry, catalysis, and organic and inorganic chemistry. The area with the most increased development is the synthesis of multicomponent crystal forms, with several groups synthesizing solvates, salts, and cocrystals in which the main objective was to improve physical properties of the active pharmaceutical ingredients. Recently, non-crystalline materials, such as ionic liquids and amorphous solid dispersions, have also been studied using mechanochemical methods. An area that is in expansion is the use of mechanochemical synthesis of bioinspired metal-organic frameworks with an emphasis in antibiotic coordination frameworks. The use of mechanochemistry for catalysis and organic and inorganic synthesis has also grown due to the synthetic advantages, ease of synthesis, scalability, sustainability, and, in the majority of cases, the superior properties of the synthesized materials. It can be easily concluded that mechanochemistry is expanding in Portugal in diverse research areas.

Efficient Screening for Ternary Molecular Ionic Cocrystals Using a Complementary Mechanosynthesis and Computational Structure Prediction Approach

The discovery of molecular ionic cocrystals (ICCs) of active pharmaceutical ingredients (APIs) widens the opportunities for optimizing the physicochemical properties of APIs whilst facilitating the delivery of multiple therapeutic agents. However, ICCs are often observed serendipitously in crystallization screens and the factors dictating their crystallization are poorly understood. We demonstrate here that mechanochemical ball milling is a versatile technique for the reproducible synthesis of ternary molecular ICCs in less than 30 min of grinding with or without solvent. Computational crystal structure prediction (CSP) calculations have been performed on ternary molecular ICCs for the first time and the observed crystal structures of all the ICCs were correctly predicted. Periodic dispersion-corrected DFT calculations revealed that all the ICCs are thermodynamically stable (mean stabilization energy=-2 kJ mol-1 ) relative to the crystallization of a physical mixture of the binary salt and acid. The results suggest that a combined mechanosynthesis and CSP approach could be used to target the synthesis of higher-order molecular ICCs with functional properties.