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Glioblastoma, a fatal brain cancer with limited treatments and poor prognosis, could benefit from targeting the L-type amino acid transporter I (LAT1). LAT1 is essential for cancer cells to acquire necessary amino acids. Tetrahydrocurcumin (THC), a key curcumin derivative, shows potential for glioblastoma treatment. However, its effectiveness is hindered by poor physicochemical and pharmacokinetic properties. Therefore, this study aims to improve the therapeutic efficacy of THC against glioblastoma by chemically modifying it to target LAT1. A novel series of THC-amino acid conjugates were synthesized by conjugating five amino acids: glycine, leucine, isoleucine, and phenylalanine to THC via carbamate bonds. The therapeutic efficacy of THC-amino acid conjugates was further examined in C6 glioma cells, including the role of LAT1 in their therapeutic effects. Among the conjugates tested, THC conjugated with two phenylalanines (THC-di-Phe) showed remarkably higher cytotoxicity against C6 glioma cells (35.8 μM) compared to THC alone (110.7 μM). THC-di-Phe induced cellular death via necrosis and apoptosis, outperforming THC. Additionally, THC-di-Phe inhibited C6 cell proliferation and migration more effectively than THC. Co-incubation of THC-di-Phe with the LAT1 inhibitor 2-Aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) further increased cellular death. THC-di-Phe also significantly inhibited the P70SK/S6 pathway, regulated by LAT1 inhibitors, more effectively than THC and displayed a similar binding mode with both JX-075 and BCH to the active site of LAT1. Findings suggest the potential role of THC-di-Phe as a LAT1 inhibitor and provide novel insight into its use as a potent antitumor agent in glioma with increased therapeutic efficacy. [ABSTRACT FROM AUTHOR]

Oxyresveratrol (ORV) is a naturally extracted compound with many pharmacological activities. However, information about the crystalline form is not known when considering the development of a form for oral dosage. Cocrystal engineering offers drug molecular understanding and drug solubility improvements. Thus, we attempted cocrystallization of ORV using 10 carboxylic acids as a coformer at a 1:1 M ratio. Each combination was processed with liquid-assisted grinding, solvent evaporation and a slurry method, then characterized by powder X-ray powder diffraction (PXRD), conventional and low-frequency Raman spectroscopy and thermal analysis. The solubility, dissolution and permeation studies across Caco-2 cell monolayers were conducted to evaluate the ORV samples. A screening study revealed that an ORV and citric acid (CTA) cocrystal formed by ethyl acetate-assisted grinding had characteristic PXRD peaks (14.0 and 16.5°) compared to those of ORV dihydrate used as a starting material. Low-frequency Raman measurements, with peaks at 100 cm -1 , distinguished potential cocrystals among three processing methods while conventional Raman could not. An endothermic melt (142.2°C) confirmed the formation of the novel crystalline complex. The solubility of the cocrystal in the dissolution media of pH 1.2 and 6.8 was approximately 1000 µg/mL, a 1.3-fold increase compared to ORV alone. In vitro cytotoxicity studies showed that the cocrystal and physical blend were not toxic at concentrations of 25 and 12.5 µM ORV, respectively. The ORV-CTA cocrystal enhanced the cellular transport of ORV across Caco-2 monolayers. Therefore, cocrystallization could be used to improve aqueous solubility and permeability, leading to better oral bioavailability of ORV.