Radical chemistry of epigallocatechin gallate and its relevance to protein damage
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Radical chemistry of epigallocatechin gallate and its relevance to protein damage. / Hagerman, Ann E; Dean, Roger T; Davies, Michael Jonathan.
In: Nitric Oxide: Biology and Chemistry, Vol. 414, No. 1, 01.06.2003, p. 115-20.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Radical chemistry of epigallocatechin gallate and its relevance to protein damage
AU - Hagerman, Ann E
AU - Dean, Roger T
AU - Davies, Michael Jonathan
PY - 2003/6/1
Y1 - 2003/6/1
N2 - The radical chemistry of the plant polyphenolics epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were investigated using electron paramagnetic resonance spectroscopy. Radical species formed spontaneously in aqueous solutions at low pH without external oxidant and were spin stabilized with Zn(II). The spectra were assigned to the gallyl radical and the anion gallyl radical, with only 10% of the signal assigned to a radical from the galloyl ester. Spectral simulations were used to establish a pK(a) of 4.8 for the EGCG radical and a pK(a) of 4.4 for the EGC radical. The electrochemical redox potentials of EGCG and EGC varied from 1000 mV at pH 3 to 400 mV at pH 8. The polyphenolics did not produce hydroxyl radicals unless reduced metal ions such as iron(II) were added to the system. Zinc(II)-stabilized EGCG radicals were more effective protein-precipitating agents than unoxidized EGCG and produced irreversibly complexed protein. EGCG and other naturally occurring polyphenolics are effective radical scavengers but their radical products have the potential to damage biological molecules such as proteins.
AB - The radical chemistry of the plant polyphenolics epigallocatechin gallate (EGCG) and epigallocatechin (EGC) were investigated using electron paramagnetic resonance spectroscopy. Radical species formed spontaneously in aqueous solutions at low pH without external oxidant and were spin stabilized with Zn(II). The spectra were assigned to the gallyl radical and the anion gallyl radical, with only 10% of the signal assigned to a radical from the galloyl ester. Spectral simulations were used to establish a pK(a) of 4.8 for the EGCG radical and a pK(a) of 4.4 for the EGC radical. The electrochemical redox potentials of EGCG and EGC varied from 1000 mV at pH 3 to 400 mV at pH 8. The polyphenolics did not produce hydroxyl radicals unless reduced metal ions such as iron(II) were added to the system. Zinc(II)-stabilized EGCG radicals were more effective protein-precipitating agents than unoxidized EGCG and produced irreversibly complexed protein. EGCG and other naturally occurring polyphenolics are effective radical scavengers but their radical products have the potential to damage biological molecules such as proteins.
KW - Antioxidants
KW - Catechin
KW - Electron Spin Resonance Spectroscopy
KW - Free Radicals
KW - Hydrogen-Ion Concentration
KW - Oxidation-Reduction
KW - Serum Albumin, Bovine
KW - Zinc Acetate
M3 - Journal article
C2 - 12745262
VL - 414
SP - 115
EP - 120
JO - Nitric Oxide: Biology and Chemistry
JF - Nitric Oxide: Biology and Chemistry
SN - 1089-8603
IS - 1
ER -
ID: 138275960