Development of a novel antioxidant assay technique based on G-quadruplex DNAzyme

Study on antioxidants' radical scavenging processes and antioxidant capabilities is important for understanding the protective role of antioxidants against oxidative damages associated with some chronic diseases and food degradation. Traditional methods to monitor the radical scavenging by antioxidant require expensive instrument and sophisticated synthesis process. Herein, we report a novel, simple, colorimetric DNAzyme-based method to detect radical-scavenging capacity of antioxidant. In this new strategy, horseradish peroxidase (HRP) mimicking DNAzyme catalyzes the oxidation of ABTS2- (2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) by H2O2 to generate blue/green ABTS.- radical, which can be scavenged by antioxidants resulting in color change. The typical kinetic curve of antioxidant-inhibited generation of ABTS.- shows distinct biphasic pattern, involving a lag phase (stage I) and a linear increase phase (stage II). kt value, the product of lag time (t) and the slope of the curve in stage II (k), was used as the parameter for antioxidant capacity determination. This DNAzyme-based antioxidant assay has been effectively used to quantitatively detect the concentrations of antioxidants and evaluate the antioxidant capabilities of a variety of antioxidants and some real samples. Compared with traditional antioxidant assays, this method is thermostable, pH stable, and time-saving, which presents a promising platform for antioxidant assay.