Preparation, physico-chemical characterization and solubility evaluation of pharmaceutical cocrystals of cinnamic acid
Trans-cinnamic acid. Coformer. Cocrystals. Physical-chemical characterization. Solubility.
Trans-cinnamic acid (CA) is a secondary metabolite found in plants and has several pharmacological activities, including antimicrobial, antifungal, antioxidant and antitumor, with low toxicity and low aqueous solubility. In this context, cocrystallization appears as an important tool to improve aqueous solubility and other physical-chemical properties, such as dissolution rate, physical and thermal stability. The objective is to prepare pharmaceutical cocrystals of CA, conduct the physico-chemical characterization and promote studies of solubility and dissolution in vitro. Pharmaceutical cocrystals were prepared by the solvent evaporation method employing stoichiometric amounts of drug and copolymer with molar ratio 1: 1. The physical-chemical characterization was based on the use of Differential Exploration Calorimetry (DSC), Thermogravimetry (TG), X-ray Diffraction (XRD) and Infrared with Fourier Transform (FTIR). The solubility evaluation was performed using the shaker-flask method for 24h in aqueous medium, with quantification in UV-vis spectrophotometry at 271.0 nm. Through the XRD analysis, the formation of three cocrystals was evaluated, characterized by the appearance of new peaks in the DRX pattern, different from the individual components. DSC curves showed a decrease in the melting temperature of the samples obtained after cocrystallization, characteristics of eutectic mixtures, being characteristic of the formation of cocrystals. TG curves showed a better thermal stability provided with the CA in the cocrystals. Through the FTIR spectrum, it was possible to evaluate the occurrence of intermolecular interactions between drug-coformers in the formed cocrystals, presenting changes in the frequency of absorption of the main functional groups involved in the formation of hydrogen bonds. A fairly significant increase in aqueous solubility of the drug was observed for the three cocrystals that were formed. Results demonstrated the importance of the use of solid state characterization techniques in the determination of new pharmaceutical cocrystals. The increase in the solubility of drugs is an important factor evaluated by cocrystals, directly influencing their oral bioavailability.