Antioxidative mechanisms of whole-apple antioxidants employing different varieties from Luxembourg

Many health beneficial functions of dietary ingredients, including antimutagenity and anticarcinogenity, have been discussed in relation to their antioxidant properties. In this study, antioxidative mechanisms of whole-apple antioxidants (from seven varieties) were investigated using the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity assay, the ferric-reducing antioxidant power (FRAP) assay, and the ferrous iron(II) chelating activity assay. Results indicated the ability of primary antioxidants to act as hydrogen or electron donors, with considerable differences depending on variety, with ABTS and FRAP values ranging from 270 to 1,142 mg of vitamin C equivalents/100 g and from 695 to 3,143 μmol of Fe/100 g, respectively. However, varieties did not display measurable chelating activity except for Florina and Graham, exhibiting a weak activity (0.1-0.2 μg of EDTA equivalents/100 g). Correlation analyses showed that polyphenols were major primary antioxidants contributing to antioxidative mechanisms (r>0.99, P<.001), whereas their involvement as secondary antioxidants (i.e., as chelating compounds) was negligible. Our findings further showed that the intake of 100 g of apple fruits can provide antioxidants equivalent to approximately 270-1,140 mg of vitamin C, with highest antioxidant concentrations for the older varieties Grauapfel and Goldparmäne.