Behaviour of Trolox with macromolecule-bound antioxidants in aqueous medium: Inhibition of auto-regeneration mechanism

•Trolox exerted antagonistic interactions with bound-antioxidants.•Antioxidant capacity changed due to concentrations of Trolox and bound-antioxidants.•pH made a significant effect on the resultant antioxidant capacity.•Inhibition of the auto-regeneration of Trolox by bound antioxidants was evidenced.

This work aimed at investigating the behaviour of Trolox, vitamin E analogue, in presence of macromolecule-bound antioxidants in aqueous radical medium. Three main groups of macromolecule-bound antioxidants were assayed: dietary fiber (DF), protein and lipid-bound antioxidants, represented by whole wheat, soybean and olive oil products, respectively. Experimental studies were carried out in aqueous ABTS (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) radical medium. Trolox and macromolecule-bound antioxidants were added to radical separately and together in different concentrations. Antioxidant capacities were determined using QUENCHER procedure. pH of radical media was altered for DF and protein-bound antioxidant studies to examine its effect. Chemometric tools were used for experimental design and multivariate data analysis. Results revealed antagonistic interactions for Trolox with all macromolecule-bound antioxidants. The reason behind this antagonism was investigated through oxidation reactions of Trolox via mass spectrometry analysis. Consequently, a proof was obtained for inhibitory effect of bound-antioxidants on auto-regeneration reactions of Trolox.