Influence of the Oxidation States of 4-Methylcatechol and Catechin on the Oxidative Stability of β-Lactoglobulin.
Chemical interactions between proteins and phenols affect the overall oxidative stability of a given biological system. To investigate the effect of protein-phenol adduct formation on the oxidative stability of β-lactoglobulin (β-LG), the protein was left to react with an equimolar concentration of 4-methylcatechol (4MC), catechin (Cat), or their respective quinone forms, 4-methylbenzoquinone (4MBQ) and catechin-quinone (CatQ), and subsequently subjected to metal-catalyzed oxidation by Fe(II)/H2O2 for 20 days at 37 °C. The reaction with 4MBQ resulted in 60% thiol loss and 22% loss of amino groups, whereas the addition of 4MC resulted in 12% thiol loss. The reaction with Cat or CatQ resulted in no apparent modification of β-LG. The oxidative stability of β-LG after reaction with each of 4MC, 4MBQ, Cat, or CatQ was impaired. Especially 4MC and 4MBQ were found to be pro-oxidative toward α-aminoadipic semialdehyde and γ-glutamic semialdehyde formation as well as the generation of fluorescent Schiff base products. The changes observed were ascribed to the redirection of oxidation as a result of the blocking of thiol groups but also to the oxidative deamination pathway, accelerating the production of semialdehydes and subsequently Schiff base structures.
Department of Food Science, Faculty of Science, University of Copenhagen , Rolighedsvej 30, 1958 Frederiksberg, Denmark.
Sisse
S
Jongberg
IPROCAR Research Institute, TECAL Research Group, University of Extremadura , 10003 Cáceres, Spain.
Mariana
M
Utrera
IPROCAR Research Institute, TECAL Research Group, University of Extremadura , 10003 Cáceres, Spain.
David
D
Morcuende
Department of Food Science, Faculty of Science, University of Copenhagen , Rolighedsvej 30, 1958 Frederiksberg, Denmark.
Marianne N
MN
Lund
Department of Food Science, Faculty of Science, University of Copenhagen , Rolighedsvej 30, 1958 Frederiksberg, Denmark.
Leif H
LH
Skibsted
IPROCAR Research Institute, TECAL Research Group, University of Extremadura , 10003 Cáceres, Spain.
Mario
M
Estévez
D002392:Catechin / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry*; D010084:Oxidation-Reduction
D002396:Catechols; D007782:Lactoglobulins; C018599:4-methylcatechol; D002392:Catechin
4-methylcatechol; catechin; metal-catalyzed oxidation; protein oxidation; quinone; β-lactoglobulin