Properties of Therapeutic Deep Eutectic Solvents of l-Arginine and Ethambutol for Tuberculosis Treatment

The treatment for tuberculosis infection usually involves a prolonged regimen of multiple antibacterial drugs, which might lead to various secondary effects. For preventing drug resistance and side-effects of anti-tuberculosis drugs, new methods for improving the bioavailability of APIs were investigated. The strategy proposed consists of the preparation of therapeutic deep eutectic solvents (THEDES), that incorporate l-arginine and ethambutol. The eutectic mixtures were prepared by mixing the components at a certain molar ratio, until a clear liquid solution was formed. The prepared mixtures were characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and nuclear magnetic resonance spectroscopy (¹H and ¹³C-NMR). The solubility and permeability of the drugs when they are in the THEDES form was evaluated at 37 °C, in phosphate buffered saline (PBS). Solubility studies showed an increase of the solubility of ethambutol when incorporated in the eutectic system. The cytotoxicity was evaluated using a model cell line (Caco-2), comparing the cytotoxicity of the API incorporated in the eutectic system. We observed that the cell viability in the THEDES was affected by the presence of citric acid, and higher cytotoxicity values were observed. Nonetheless, these findings do not compromise the possibility to use these systems as new delivery systems for ethambutol and arginine.

Design, synthesis and evaluation of N13-substituted evodiamine derivatives against human cancer cell lines

Attempting to improve the anticancer activity and solubility of evodiamine in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) solutions, thirty-eight N13-substituted evodiamine derivatives were designed, synthesized and tested for antitumor activities against six kinds of human cancer cell lines, namely prostate cancer (DU-145 and PC-3), lung cancer (H460), breast cancer (MCF-7), colon cancer (HCT-5) and glioblastoma (SF-268). The solubility of these compounds in SGF and SIF solutions was evaluated, and apoptosis induced by 2-2, 2-3, 2-16 and 3-2 was determined. The results showed: (1) among all compounds examined, 2-16 showed the highest antitumor activity and a broader spectrum of activity, with IC₅₀ values ranging from 1–2 µM; (2) their solubility was obviously improved; (3) 2-3, 2-16 and 3-2 had a significant impact inducing apoptosis in some cancer cell lines. The preliminary structure-activity relationships of these derivatives were discussed.