title: Grape skins (Vitis vinifera L.) catalyze the in vitro enzymatic hydroxylation of p-coumaric acid to caffeic acid.
abstract: The ability of grape skins to catalyze in vitro conversion of p-coumaric acid to the more potent antioxidant caffeic acid was studied. Addition of different concentrations of p-coumaric to red grape skins (Cabernet Sauvignon) resulted in formation of caffeic acid. This caffeic acid formation (Y) correlated positively and linearly to p-coumaric acid consumption (X): Y = 0.5 X + 9.5; R (2) = 0.96, P < 0.0001. The kinetics of caffeic acid formation with time in response to initial p-coumaric acid levels and at different grape skin concentrations, indicated that the grape skins harboured an o-hydroxylation activity, proposedly a monophenol- or a flavonoid 3'-monooxygenase activity (EC 1.14.18.1 or EC 1.14.13.21). The K (m) of this crude o-hydroxylation activity in the red grape skin was 0.5 mM with p-coumaric acid.
authors.affiliation: Department of Chemical and Biochemical Engineering, Center for BioProcess Engineering, Building 229, Technical University of Denmark, 2800, Kgs. Lyngby, Denmark.
authors.forename: Anis
authors.initials: A
authors.lastname: Arnous
authors.forename: Anne S
authors.initials: AS
authors.lastname: Meyer
mesh_terms: D002109:Caffeic Acids / Q000378:metabolism*; D003373:Coumaric Acids / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D006900:Hydroxylation; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D011422:Propionates; D013997:Time Factors; D027843:Vitis / Q000378:metabolism*
chemical_list: D002109:Caffeic Acids; D003373:Coumaric Acids; D010940:Plant Proteins; D011422:Propionates; D003577:Cytochrome P-450 Enzyme System; C038888:flavonoid 3'-hydroxylase; D014442:Monophenol Monooxygenase; C495469:p-coumaric acid; C040048:caffeic acid