New tool to evaluate a comprehensive antioxidant activity in food extracts: bleaching of 4-nitroso-N,N-dimethylaniline catalyzed by soybean lipoxygenase-1.

In this study the 4-nitroso-N,N-dimethylaniline (RNO) bleaching associated with linoleic acid hydroperoxidation catalyzed by the soybean lipoxygenase (LOX)-1 isoenzyme (LOX/RNO reaction) was used to determine the antioxidant activity (AA) of hydrophilic and lipophilic pure antioxidant compounds and of mixtures of antioxidants extracted from durum wheat whole flour (DWWF). By means of a simple and rapid experimental protocol (about 3 min/assay), the LOX/RNO reaction may simultaneously detect many antioxidant functions (scavenging of some physiological radical species, iron ion reducing and chelating activities, inhibition of the pro-oxidant apoenzyme), thus providing a comprehensive AA evaluation. Consistently, the LOX/RNO assay was very sensitive to hydrophilic, lipophilic, and phenolic antioxidant extracts from DWWF, providing AA values at least 35 and 30 times higher than those by TEAC and ORAC methods, respectively. Moreover, the new method was able to highlight synergism (among extracts) 3 times more than the ORAC method, whereas TEAC did not measure synergism under our experimental conditions.