Maniçoba, a quercetin-rich Amazonian dish

A large quantity of quercetin was characterized from a local dish known as maniçoba in Pará, Brazil. The fresh leaf of Manihot esculenta Crantz (Euphorbiaceae), a principal ingredient for maniçoba, was found to contain a large amount of rutin or quercetin 3-O-rutinoside which was completely hydrolyzed to quercetin during cooking processes. Antioxidant activity of quercetin and its microfloral metabolites was examined. Quercetin scavenged the superoxide anion generated by xanthine oxidase (EC 1.1.3.22) and inhibited uric acid formation on xanthine oxidase, while rutin scavenged the superoxide anion but without inhibiting the enzyme. 3,4-Dihydroxyphenylacetic acid, a microfloral metabolite of quercetin, also scavenged the superoxide anion generated by xanthine oxidase and inhibited uric acid formation on xanthine oxidase. In addition, quercetin inhibited the oxidation of linoleic acid catalyzed by soybean lipoxygenase-1 (EC 1.13.11.12, Type 1).