Microplate ORAC-pyranine spectrophotometric assay for high-throughput assessment of antioxidant capacity

•The target molecule defines free-radical scavenging mechanisms in ORAC assays.•Pyranine reports on stoichiometry and pyrogallol red accounts on chemical reactivity.•Microchemical analysis of ORAC-pyranine with green chemistry features.•Dual-probe approach for comparative study of structure-antioxidant activity.•Application to complex samples, including antioxidant-rich beverages.