Determination of the p Ka Values of trans-Resveratrol, a Triphenolic Stilbene, by Singular Value Decomposition. Comparison with Theory

László Zimányi; Shareefa Thekkan; Brett Eckert; Alanna R Condren; Olga Dmitrenko; Leah R Kuhn; Igor V Alabugin; Jack Saltiel

doi:10.1021/acs.jpca.0c04792

Determination of the p K_a Values of trans-Resveratrol, a Triphenolic Stilbene, by Singular Value Decomposition. Comparison with Theory

J Phys Chem A. 2020 Aug 6;124(31):6294-6302. doi: 10.1021/acs.jpca.0c04792. Epub 2020 Jul 22.

Authors

László Zimányi¹, Shareefa Thekkan², Brett Eckert², Alanna R Condren², Olga Dmitrenko³, Leah R Kuhn², Igor V Alabugin², Jack Saltiel²

Affiliations

¹ Institute of Biophysics, Biological Research Centre, P.O. Box 521, Szeged, Hungary H-6701.
² Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States.
³ Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.

PMID: 32635729
DOI: 10.1021/acs.jpca.0c04792

Abstract

Several independent determinations of the pK_a values of trans-resveratrol in water have led to conflicting results. Singular value decomposition analysis of UV absorption spectra of trans-resveratrol (t-Resv) in N₂-outgased aqueous solutions buffered to pH values in the 7.0-13.6 range yielded the UV spectra of the three anionic forms and the corresponding pK_a values: pK_a1 = 9.1₆, pK_a2 = 9.7₇, and pK_a3 = 10.5₅ in very good agreement with calculated theoretical values. The analysis of the absorption spectra guided the assignment of the fluorescence spectrum of each anionic form. With the resolved spectra on hand, we applied the Förster equation to estimate pK_a* values of 2.5 and 0, respectively, for the p- and m-OH substituents of t-Resv in S₁. Theory supports a proposed mechanism for the reaction of t-Resv anions with O₂.