PubMed:15388161 JSONTXT

{"target":"http://pubannotation.org/docs/sourcedb/PubMed/sourceid/15388161","sourcedb":"PubMed","sourceid":"15388161","source_url":"http://www.ncbi.nlm.nih.gov/pubmed/15388161","text":"Oxidation products of quercetin catalyzed by mushroom tyrosinase.\nQuercetin was oxidized as a substrate catalyzed by mushroom tyrosinase to the corresponding o-quinone and subsequent isomerization to p-quinone methide type intermediate; followed by the addition of water on C-2 yielding a relatively stable intermediate, 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone. In the presence of a catalytic amount of l-DOPA as a cofactor, the rate of this oxidation was enhanced. Fisetin, which lacks the C-5 hydroxyl group, was also oxidized but the rate of oxidation was faster than that of quercetin, indicating that the C-5 hydroxyl group is not essential but is associated with the activity.","tracks":[]}