Biomass‐Derived Carbon Dots–Based FRAP Analog for Sensitive Evaluation of Antioxidant Activity: Application to Pharmaceutical Products and Plant Extracts

ABSTRACT

Ferric reducing antioxidant power (FRAP) is a well‐established antioxidant in vitro assay. This work introduces an innovative FRAP‐analog assay based on green‐synthesized carbon dots (GCDs) for the sensitive evaluation of antioxidant activity. The GCDs were prepared via ordinary roasting of sweet potato, which is considered a natural and renewable precursor, yielding highly fluorescent (quantum yield 53%), water‐soluble CDs with excellent ferric (Fe ³⁺ ) complexing activity. In this system, the addition of Fe ³⁺ leads to quenching of the fluorescence of GCDs. Antioxidant‐induced reduction of Fe ³⁺ to Fe ²⁺ leads to a measurable turn on effect. Using ascorbic acid as a reference antioxidant, the sensor exhibited a linear response between 2 and 14 μg/mL ( R ² 0.996) with a limit of detection of 0.82 μg/mL, very good accuracy (recovery = 103.27% ± 3.48%) and acceptable precision (RSD = 1.01%–5.61%). The developed assay was applied successfully to pharmaceutical products and plant extracts. The GCD‐based FRAP analog demonstrated strong correlation with traditional FRAP assays. The devised approach eliminated the use of toxic nonrenewable reagents, rendering it excellent green on both analytical Eco‐scale, Analytical GREEnness (AGREE), and Nano Eco‐Scale metrics. This green, nanomaterial‐based approach provides a promising alternative for antioxidants' analysis in food and pharmaceuticals.