Abstract

Hydrogen atom transfer (HAT) underlies free-radical chain-breaking by phenolic compounds. Using linear free energy relationship (LFER) analysis, proton transfer kinetics was hypothesized as a surrogate rate process for HAT. Phenol red is a probe that is easily oxidized to highly absorbing specie by hydroxyl ion. Absorbance decay of oxidized phenol red was induced by incremental proton transfer from a model phenolic (resorcinol). Global best-fit kinetics profile of resorcinol approximates a mono-exponential decay model (R² = 0.991) as a limiting law. Proton transfer rate constant (K_ptt) versus concentration reveal the utility of the slope (α_aoc) of the linear plot (r²= 0.990) as a sensitive predictor of phenolic antioxidant capacity. Superior antioxidant capacity profile of a polyphenol-rich dietary supplement: Garcinia kola seed extract, optimally obeyed a mixed linear/mono-exponential decay equation. Model robustness and selectivity for phenolics was achieved by specifying mathematical constraints as acceptance criteria. The method is more biologically relevant for chain-breaking antioxidants than free-radical-based assays because it captures antioxidant structure-function relationships. Further validation studies, using structurally diverse polyphenols, are warranted to ascertain general utility of the kinetic assay for achieving quality by design (QbD) in phenolic dietary supplement products.

Recommended Citation

Idowu, Sunday O.; Adeyemo, Morenikeji A.; and Itiola, Ademola J. (2009) "Computational Models for the Determination of Antioxidant Capacity and Phenolics in Dietary Supplements Using Real-Time Proton Transfer Kinetics Data," Chemical Product and Process Modeling: Vol. 4 : Iss. 1, Article 41.
DOI: 10.2202/1934-2659.1385
Available at: http://www.bepress.com/cppm/vol4/iss1/41