Indole-Derived Compounds as Redox-Modulators: Antioxidant Mechanisms in Neuronal Protection

Neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Amyotrophic lateral sclerosis, are distinguished by progressive neuronal dysfunction caused primarily by oxidative stress, mitochondrial impairment, neuroinflammation, and redox imbalance. Growing evidence suggests that indole-derived compounds have significant neuroprotective potential due to their antioxidant, anti-inflammatory, and redox-modulating properties. This review summarizes the structural and biological significance of indole scaffolds, focusing on the mechanisms by which natural, endogenous, microbiota-derived, and synthetic indole compounds protect neuronal networks. Indole-3-carbinol, 3,3'-diindolylmethane, indole-3-propionic acid, and melatonin are major indole derivatives that control important neuroprotective pathways like Nrf2/ARE signaling, mitochondrial bioenergetics, neurotrophic factor expression, apoptotic regulation, and suppression of proinflammatory mediators. These compounds also maintain synaptic plasticity, reduce reactive oxygen species production, and improve neuronal survival in neurodegenerative disease models. Additionally, updated information from translational and clinical research indicates that indole-based compounds may have promising therapeutic applications; however, obstacles like low bioavailability, metabolic instability, and blood-brain barrier penetration continue to be major obstacles to clinical application. Development in nanoparticle delivery systems, microbiome-targeted interventions, and rational structural optimization may improve therapeutic efficacy and translational potential. Overall, indole-derived compounds are a versatile class of redox modulators with potential applications in the prevention and treatment of neurodegenerative diseases via integrated antioxidant and neuroprotective mechanisms.