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 inhibited the oxidation of linoleic acid catalyzed by soybean lipoxygenase-1 (EC 188.8.131.52, Type 1) with an IC50 of 4.5 μM, while rutin did not inhibit this oxidation up to 200 μM. The progress curves for the enzyme reaction indicate that quercetin shows slow binding kinetics. In the pseudoperoxidase activity, hydroperoxides slowly oxidize quercetin to a rather stable intermediate, 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone. A microfloral metabolite of quercetin and rutin after ingestion, 3,4-dihydroxyphenylacetic acid, also scavenged superoxide anion generated by xanthine oxidase and inhibited uric acid formation. The antioxidant activity observed with the methanol extract of maniçoba is due mainly to multifunctional quercetin's response.
|Title of host publication||Quercetin|
|Subtitle of host publication||Dietary Sources, Functions and Health Benefits|
|Publisher||Nova Science Publishers, Inc.|
|Number of pages||26|
|Publication status||Published - Dec 1 2012|
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