Determination of total antioxidant capacity of Cynara Scolymus L. (globe artichoke) by using novel nanoparticle-based ferricyanide/Prussian blue assay

A novel ferricyanide/Prussian blue (PB) assay for total antioxidant capacity (TAC) determination was developed exploiting the formation of PB nanoparticles in the presence of polyvinylpyrrolidone (PVP) as stabilizer. This improved method, named as "nanoparticle-based ferricyanide/Prussian blue assay (PBNP)", was applied to the TAC measurement of Cynara Scolymus L. (globe artichoke). The calibration results of the novel (PBNP) method were compared with those of a similar nanoparticle PB method performed in the absence of PVP, and of a sodium dodecyl sulfate-modified and acid-optimized ferricyanide reference assay. Compared to similar common Fe(III)-based TAC assays, much higher molar absorptivities, pointing out higher response to different kinds of antioxidants, were obtained with PBNP for all tested antioxidants, and lower LOD and LOQ values were achieved for thiols. As an additional advantage, methionine, not responding to other electron-transfer based TAC reagents, could be measured. PBNP could detect various antioxidants with one-two orders-of-magnitude lower LOD values than those of widely used TAC assays like CUPRAC and Folin-Ciocalteau well correlating with the proposed assay.