TY - JOUR
T1 - Beer-thiol-containing compouds and redox stability
T2 - kinetic study of 1-Hydroxyethyl radical scavenging ability
AU - Almeida, Natália E.C. de
AU - Lametsch, Marianne Lund
AU - Andersen, Mogens Larsen
AU - Cardoso, Daniel R.
PY - 2013/10/2
Y1 - 2013/10/2
N2 - The 1-hydroxyethyl radical is a central intermediate in oxidative reactions occurring in beer. The reactivity of thiol-containing compounds toward 1-hydroxyethyl radical was evaluated in beer model solutions using a competitive kinetic approach, employing the spin-trap 4-POBN as a probe and by using electron paramagnetic resonance to detect the generated 1-hydroxyethyl/4-POBN spin adduct. Thiol-containing compounds were highly reactive toward the 1-hydroxyethyl radical with apparent second-order rate constants close to the diffusion limit in water and ranging from 0.5 × 109 L mol -1 s-1 for the His-Cys-Lys-Phe-Trp-Trp peptide to 6.1 × 109 L mol-1 s-1 for the reduced lipid transfer protein 1 (LTP1) isolated from beer. The reactions gave rise to a moderate kinetic isotope effect (kH/kD = 2.3) suggesting that reduction of the 1-hydroxyethyl radical by thiol-containing compounds takes place by hydrogen atom abstraction from the RSH group rather than electron transfer. The content of reduced thiols in different beers was determined using a previously established method based on ThioGlo-1 as the thiol derivatization reagent and detection of the derivatized thiols by reverse-phase liquid chromatography coupled to a fluorescence detector. The total level of thiol in beer (oxidized and reduced) was determined after a reduction step employing 3,3′,3″-phosphanetriyltripropanoic acid (TCEP) as the disulfide reductant. A good correlation among total protein and total thiol content in different beers was observed. The results suggest a similar ratio between reduced thiols and disulfides in all of the tested beers, which indicates a similar redox state.
AB - The 1-hydroxyethyl radical is a central intermediate in oxidative reactions occurring in beer. The reactivity of thiol-containing compounds toward 1-hydroxyethyl radical was evaluated in beer model solutions using a competitive kinetic approach, employing the spin-trap 4-POBN as a probe and by using electron paramagnetic resonance to detect the generated 1-hydroxyethyl/4-POBN spin adduct. Thiol-containing compounds were highly reactive toward the 1-hydroxyethyl radical with apparent second-order rate constants close to the diffusion limit in water and ranging from 0.5 × 109 L mol -1 s-1 for the His-Cys-Lys-Phe-Trp-Trp peptide to 6.1 × 109 L mol-1 s-1 for the reduced lipid transfer protein 1 (LTP1) isolated from beer. The reactions gave rise to a moderate kinetic isotope effect (kH/kD = 2.3) suggesting that reduction of the 1-hydroxyethyl radical by thiol-containing compounds takes place by hydrogen atom abstraction from the RSH group rather than electron transfer. The content of reduced thiols in different beers was determined using a previously established method based on ThioGlo-1 as the thiol derivatization reagent and detection of the derivatized thiols by reverse-phase liquid chromatography coupled to a fluorescence detector. The total level of thiol in beer (oxidized and reduced) was determined after a reduction step employing 3,3′,3″-phosphanetriyltripropanoic acid (TCEP) as the disulfide reductant. A good correlation among total protein and total thiol content in different beers was observed. The results suggest a similar ratio between reduced thiols and disulfides in all of the tested beers, which indicates a similar redox state.
U2 - 10.1021/jf402159a
DO - 10.1021/jf402159a
M3 - Journal article
C2 - 24007263
SN - 0021-8561
VL - 61
SP - 9444
EP - 9452
JO - Journal of Agricultural and Food Chemistry
JF - Journal of Agricultural and Food Chemistry
IS - 39
ER -