Beyond Bulk Oxidative Stress: Why Antioxidant Therapies Fail and Redox Biomarkers Disappoint

Reactive oxygen species (ROS), reactive nitrogen species (RNS) and reactive sulphur species (RSS) constitute a coupled molecular language whose marks, the reversible post-translational modifications of cysteine and tyrosine residues, are formed, interconverted and reversed within subcellular microdomains characterised by their own geometry and kinetics. Two decades of broad-spectrum antioxidant clinical trials using vitamin E, beta-carotene, and N-acetylcysteine, amongst other compounds, have produced predominantly neutral and in some settings harmful results, although the outcomes vary appreciably with the compound, the disease, the dose and the trial design, and several of the most studied polyphenols, curcumin, resveratrol and quercetin, display a broadly comparable pattern, compounded in their case by low oral bioavailability of the parent aglycone, which limits the concentration reaching the target tissue. The redox biomarkers available in clinical practice, plasma GSH/GSSG, urinary 8-oxo-dG, and serum MDA, show disappointing individual prognostic value. The present work argues that both failures are consistent with a shared mechanistic explanation: they treat the redox language as undifferentiated noise when it is, in fact, spatially structured information. While other contributing factors, including analytical variability, clinical heterogeneity, and cohort design, are acknowledged, this mechanistic convergence offers a parsimonious interpretive framework. We analyse the failure of global antioxidants from the logic of the microdomain, suggesting that non-specific scavenging suppresses eustress and distress with comparable efficacy, and the failure of conventional redox biomarkers from the loss of spatial and temporal resolution that occurs when signals from multiple compartments are collapsed into a systemic index. Building upon this dual analysis, we propose the principles of an alternative strategy: pharmacological interventions acting on specific microdomain levers (NOS recoupling, restoration of mitochondrial -SSH tone, and Prx/Trx system support) and a precision redox diagnostic framework that replaces global indices with compartment-resolved biomarker panels. The objective is not to silence the redox language, but to learn to read it and, when necessary, to correct its grammar with precision.