Charge equilibria and pKa of malvidin-3-glucoside by electrophoresis
Date
2003
Authors
Asenstorfer, R.
Iland, P.
Tate, M.
Jones, G.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Analytical Biochemistry, 2003; 318(2):291-299
Statement of Responsibility
Robert E. Asenstorfer, Patrick G. Iland, Max E. Tate and Graham P. Jones
Conference Name
Abstract
Paper electrophoresis has been used over the pH range 1.2 to 10.4 to measure apparent pKa values for malvidin-3-O-glucoside of pKa1 1.76 ± 0.07, pKa2 5.36 ± 0.04, and pKa3 8.39 ± 0.07. Using solvent partitioning between buffered aqueous solutions and n-octanol, several micro-pKa constants for malvidin-3-O-glucoside were also identified, highlighting the complex nature of malvidin-3-glucoside equilibria. As a nonspectrophotometric procedure, the charge-dependent electrophoretic mobility method provided independent information on the net charge and color of anthocyanin species at wine pH (ca. 3.6). At this pH, the color of malvidin-3-glucoside in red wines is consistent only with the uncharged quinonoidal base as a major colored component of the equilibria.