title: Antioxidative compounds from the outer scales of onion.
abstract: Antioxidative compounds were isolated from the methanol extract of dry outer scales of onion (Allium cepa L.). Nine phenolic compounds (1-9) were finally obtained by reversed-phase high-performance liquid chromatography, and their structures were elucidated by NMR and mass spectrometry analyses. They were the six known compounds, protocatechuic acid (1), 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (2), quercetin 4'-O-beta-D-glucopyranoside (3), quercetin (5), 4'-O-beta-d-glucopyranoside of quercetin dimer (7), and quercetin dimer (8), and three novel compounds, condensation products of quercetin with protocatechuic acid (4), adduct of quercetin with quercetin 4'-O-beta-D-glucopyranoside (6), and quercetin trimer (9). These phenolic compounds were tested for their antioxidant properties using autoxidation of methyl linoleate in bulk phase or free radical initiated peroxidation of soybean phosphatidylcholine in liposomes. The flavonoid compounds having o-dihydroxy substituent in the B-ring were shown to be effective antioxidants against nonenzymic lipid peroxidation.
authors.affiliation: Department of Applied Life Science, Faculty of Applied Biological Sciences, and Division of Instrumental Analysis, Life Science Research Center, Gifu University, 1-1 Yanagido, Gifu City, Gifu 501-1193, Japan.
authors.forename: Tram Ngoc
authors.initials: TN
authors.lastname: Ly
authors.forename: Chiharu
authors.initials: C
authors.lastname: Hazama
authors.forename: Makoto
authors.initials: M
authors.lastname: Shimoyamada
authors.forename: Hiromune
authors.initials: H
authors.lastname: Ando
authors.forename: Koji
authors.initials: K
authors.lastname: Kato
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamauchi
mesh_terms: D000975:Antioxidants / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D005419:Flavonoids / Q000032:analysis / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D019697:Onions / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry*; D011794:Quercetin / Q000031:analogs & derivatives / Q000032:analysis / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D011794:Quercetin