title: Fermentation enhances the in vitro antioxidative effect of onion (Allium cepa) via an increase in quercetin content.
abstract: Yellow onion (Allium cepa) extract showed enhanced antioxidative effects in 2,2-diphenyl-1-picrylhydrazyl (DPPH), Trolox equivalent antioxidant capacity (TEAC) and 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate and acetyl ester (CM-H(2)DCFDA) assay after being treated with a crude enzyme extract from soybean paste fungi, Aspergillus kawachii. HPLC analysis showed two increased and two decreased peaks after enzyme treatment. The decreased peaks were identified as quercetin-3,4'-di-O-β-d-glucoside (1) and quercetin-4'-O-β-d-glucoside (2), and peaks that increased were quercetin-3-O-β-d-glucoside (3) and quercetin (4), respectively. It was expected that 3 and 4 were originated from the glucosidic cleavage of their glucosides, 1 and 2. Among the increased compounds, only quercetin (4) showed strong antioxidative activity in the DPPH assay. In addition, the protective effect against glutamate-induced neurotoxicity in HT22 cells was increased when treated with 25 μg/ml of fermented onion. The enhanced neuroprotective effect was also originated from the increased quercetin content. As a consequence, fermentation raised the quercetin content in onion, and subsequently increased the antioxidative and neuroprotective activities.
authors.affiliation: BK21 Research Team for Developing Functional Health Food Materials, Kyungpook National University, 1370, Sankyuk-Dong, Daegu 702-701, Republic of Korea.
authors.forename: Eun-Ju
authors.initials: EJ
authors.lastname: Yang
authors.forename: Sang-In
authors.initials: SI
authors.lastname: Kim
authors.forename: Sang-Yun
authors.initials: SY
authors.lastname: Park
authors.forename: Han-Yeol
authors.initials: HY
authors.lastname: Bang
authors.forename: Ji Hye
authors.initials: JH
authors.lastname: Jeong
authors.forename: Jai-Hyun
authors.initials: JH
authors.lastname: So
authors.forename: In-Koo
authors.initials: IK
authors.lastname: Rhee
authors.forename: Kyung-Sik
authors.initials: KS
authors.lastname: Song
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology*; D001230:Aspergillus / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism; D001713:Biphenyl Compounds / Q000737:chemistry; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D005285:Fermentation; D047309:Flavones / Q000032:analysis; D005511:Food Handling; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology; D051379:Mice; D018696:Neuroprotective Agents / Q000494:pharmacology; D019697:Onions / Q000737:chemistry*; D010851:Picrates / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology; D011794:Quercetin / Q000737:chemistry*; D012997:Solvents
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D047309:Flavones; D016166:Free Radical Scavengers; D018696:Neuroprotective Agents; D010851:Picrates; D010936:Plant Extracts; D012997:Solvents; D011794:Quercetin; C004931:1,1-diphenyl-2-picrylhydrazyl