Exploring the potential anti-thyroid activity of Acetyl-L-carnitine: Lactoperoxidase inhibition profile, iodine complexation and scavenging power against H2O2. Experimental and theoretical studies.

L-Acetylcarnitine (ALC), a versatile compound, has demonstrated beneficial effects in depression, Alzheimer's disease, cognitive impairment, and other conditions. This study focuses on its antithyroid activity. The precursor molecule, L-carnitine, inhibited the uptake of triiodothyronine (T3) and thyroxine (T4), and it is possible that ALC may reduce the iodination process of T3 and T4. Currently, antithyroid drugs are used to control the excessive production of thyroid hormones (TH) through various mechanisms: (i) forming electron donor-acceptor complexes with molecular iodine, (ii) eliminating hydrogen peroxide, and (iii) inhibiting the enzyme thyroid peroxidase. To understand the pharmacological properties of ALC, we investigated its plausible mechanisms of action. ALC demonstrated the ability to capture iodine (Kc = 8.07 ± 0.32 x 105 M-1), inhibit the enzyme lactoperoxidase (LPO) (IC50 = 17.60 ± 0.76 µM), and scavenge H2O2 (39.82 ± 0.67 mM). A comprehensive physicochemical characterization of ALC was performed using FTIR, Raman, and UV-Vis spectroscopy, along with theoretical DFT calculations. The inhibition process was assessed through fluorescence spectroscopy and vibrational analysis. Docking and molecular dynamics simulations were carried out to predict the binding mode of ALC to LPO and to gain a better understanding into the inhibition process. Furthermore, albumin binding experiments were also conducted. These findings highlight the potential of ALC as a therapeutic agent, providing valuable insights for further investigating its role in the treatment of thyroid disorders.

Copper-flavonoid family of complexes involved in alkaline phosphatase activation.

The flavonoid naringenin and a family of naringenin derivative Cu(II) complexes having phenanthroline-based second ligands were selected to study alkaline phosphatase activation. This enzyme plays a critical role in tissue formation, increasing the inorganic phosphate formation, favoring mineralization, and being essential to producing bone mineralization. The effects of those compounds on the function and structure of the enzyme were evaluated by kinetic measurements, fluorescence, FTIR, and UV-Vis spectroscopies. The results showed that naringenin did not affect alkaline phosphatase activity, having a value of the Michaelis-Menten-constant close to the enzyme (Km = 3.07 × 10-6). The binary complex, Cu(II)-naringenin, and the ternary complex Cu(II)-naringenin-phenanthroline behaved as an enzyme activator in all the concentrations range used in this study. Those complexes increased in c.a. 1.9% the catalytic efficiency concerning enzyme and naringenin. The ternary complex Cu(II)-naringenin-bathophenanthroline, provokes an activator mixed effect, dependent on the substrate concentrations. The different kinetic behavior can be correlated with different conformational changes observed under the interaction with ALP. Fluorescence experiments showed a raising of the binding constant with temperature. FTIR determinations showed that the complex with bathophenanthroline modifies the ALP structure but maintains the helical structure. The other copper complexes provoked a structural unfolding, decreasing the α-helix content. None of them affect the dephosphorylation enzyme ability. Even though the interactions and structural modifications on ALP are different, it is evident that the presence of copper favors enzymatic activity. The observed electrostatic interactions probably benefit the dissociation of the bound phosphate. The results suggest potential biological applications for the studied compounds.

Copper(II) cation and bathophenanthroline coordination enhance therapeutic effects of naringenin against lung tumor cells.

The development of new anticancer compounds is one of the challenges of bioinorganic and medicinal chemistry. Naringenin and its metal complexes have been recognized as promising inhibitors of cell proliferation, having enormous potential to act as an antioxidant and antitumorigenic agent. Lung cancer is the second most commonly diagnosed type of cancer. Therefore, this study is devoted to investigate the effects of Cu(II), naringenin (Nar), binary Cu(II)-naringenin complex (CuNar), and the Cu(II)-naringenin containing bathophenanthroline as an auxiliary ligand (CuNarBatho) on adenocarcinoma human alveolar basal epithelial cells (A549 cells) that are used as models for the study of drug therapies against lung cancer. The ternary complex shows selectivity being high cytotoxic against malignant cells. The cell death generated by CuNarBatho involves ROS production, loss of mitochondrial membrane potential, and depletion of GSH level and GSH/GSSG ratio. The structure-relationship activity was assessed by comparison with the reported Cu(II)-naringenin-phenanthroline complex. The CuNarBatho complex was synthesized and characterized by elemental analysis, molar conductivity, mass spectrometry, thermogravimetric measurements and UV-VIS, FT-IR, EPR, Raman and 1H-NMR spectroscopies. In addition, the binding to bovine serum albumin (BSA) was studied at the physiological conditions (pH = 7.4) by fluorescence spectroscopy.