Chelation studies have been underestimated among antioxidant activities evaluation and the measurement of chelation % is incompariable among published studies. There is limited data regarding chelation ability of olive pomace (OP). We evaluated Iron(II) chelation using chemical standards of olive phenolics to investigate olive phenolics chelation ability and to provide OP chelation data. Chemical standards of OP were analyzed for iron chelation ability in mM Iron(II)/ mM molecule through a Ferrozine-iron complex assay in pH 3.78 and 6.81 in triplicates and a phenolic concentration range of 0.04-0.5 mM. The standard curves showed no changes in absorption due to pH. A least significant difference (LSD) test at α=0.05 was performed to compare significant differences. High chelation OP phenolics were determined to include caffeic acid (0.9942 mM Iron(II)/ mM molecule) and verbascoside (1.047 mM Iron(II)/ mM molecule) both at pH 6.81 in which there is no significant difference as compared to gallic acid at pH 6.81 (0.9708 mM Iron(II)/ mM molecule). At pH 3.78, caffeic acid, verbascoside, and gallic acid had values of (0.123 mM Iron(II)/ mM molecule), (-0.113 mM Iron(II)/ mM molecule), and (-0.067 mM Iron(II)/ mM molecule) respectively. At pH 3.78, all the chelating ability significantly reduced. This assay would be used as a standardized protocol for the comparison of chelating ability among studies. The assay responsiveness to pH buffers allows for the potential for this method to be adopted in studies with different pH environments. Discovery of high chelation compounds in OP would allow repurposing and waste reduction of OP by-products as effective chelation reagents for inhibition of oxidative stress in both biological and oleaginous food systems as means of protection and preservation.

Reevaluation of Ferrozine assay for rapid testing iron(II) chelation ability of phenolics in mole ratio: Case study by evaluating chelation of chemical standards of olive phenolics

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