Hydrazide-hydrazones as novel antioxidants - in vitro, molecular docking and DFT studies

The pathogenesis of many diseases, such as obesity, depression, cancer, cataract, and neurodegenerative diseases, is related to the generation of reactive oxygen species (ROS). Structures possessing radical-scavenging properties act as antioxidants and they could prevent the progression of the aforementioned diseases. Therefore, the current work was focused on the resynthesis and the antioxidant evaluation of 13 hydrazide-hydrazones. Two in vitro tests - DPPH and ABTS, were applied for the determination of the antioxidant capacities. The free-radical scavenging assays displayed that the hydrazide-hydrazone synthesized after condensation with a salicylaldehyde (5b) is the most potent antioxidant. The in vitro evaluation through the ABTS test showed that the former structure has greater antioxidant properties compared with the used standard - Trolox (6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid). In concentrations of 31 µM, the pyrrole-based structure showed 35.77% radical-scavenging effects. A possible binding conformation of the most active hydrazide-hydrazone in the active site of NADPH oxidase was visualised through docking simulations. The active amino acids involved in the stabilisation of the complexes were discussed. DFT studies demonstrated that 5b is a stable structure with good hydrogen and electron donating properties. Overall, the pyrrole-based hydrazide-hydrazone possesses promising antioxidant properties, however further in vitro/in vivo biological evaluations are required.