Design and Synthesis of Caffeine-Based Derivatives with Antioxidant and Neuroprotective Activity: In Vitro Evaluation...

Oxidative stress and excitotoxicity are key contributors to neuronal damage in various neurodegenerative diseases. Caffeine, a widely used neuroactive compound with moderate antioxidant properties, may benefit from structural modifications to enhance its neuroprotective potential. In this study, a series of novel caffeine derivatives was synthesized and evaluated for antioxidant and potential neuroprotective relevance using in vitro models of oxidative stress and glutamate-induced excitotoxicity in SH-SY5Y human neuroblastoma cells. Antioxidant capacity was assessed using ABTS•⁺ radical cation decolorization and DPPH radical scavenging assays. Most derivatives exhibited strong free radical scavenging activity, surpassing both caffeine and the reference antioxidant Trolox at low concentrations (5 µM). Notably, compounds AL-7, AL-8, AL-9, and AL-10 demonstrated particularly high activity. Cytotoxicity evaluation using the MTT assay revealed low toxicity for all compounds, with calculated IC₅₀ values above 500 µM. Intracellular reactive oxygen species (ROS) levels measured by the DCFH-DA assay showed that several derivatives, especially AL-4, significantly reduced H₂O₂-induced oxidative stress. In neuroprotection assays, compounds AL-0, AL-1, and AL-4 markedly protected against hydrogen peroxide-induced damage, restoring cell viability up to 73%, while AL-7 achieved up to 85% protection against L-glutamate-induced excitotoxicity, outperforming caffeine. In silico SwissADME analysis indicated favorable oral bioavailability, with predicted gastrointestinal absorption and limited blood-brain barrier permeability. Overall, these findings highlight structurally modified caffeine derivatives as promising antioxidant and neuroprotective agents warranting further mechanistic and therapeutic investigation.