title: Isolation and identification of an antioxidant flavonoid compound from citrus-processing by-product.
abstract: BACKGROUND
  Large amounts of citrus by-products are released from juice-processing plants every year. Most bioactive compounds are found in the peel and inner white pulp. Flavonoids are a widely distributed group of bioactive compounds. The methanolic extract of citrus peel powder has been shown to possess strong antioxidant activity. Therefore the aim of this study was to isolate the major antioxidant flavonoid compound from Citrus unshiu (satsuma) peel as citrus by-product and evaluate its antioxidant activity.
  
  
  RESULTS
  The major flavonoid isolated from C. unshiu peel was identified as quercetagetin. The structure of the compound was determined by tandem mass spectrometry and ultraviolet spectroscopy. Its antioxidant activity was assessed by assays of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, hydroxyl radical and intracellular reactive oxygen species (ROS) scavenging and DNA damage inhibition. Quercetagetin showed strong DPPH radical-scavenging activity (IC₅₀ 7.89 µmol L⁻¹) but much lower hydroxyl radical-scavenging activity (IC₅₀ 203.82 µmol L⁻¹). Furthermore, it significantly reduced ROS in Vero cells and showed a strong protective effect against hydrogen peroxide-induced DNA damage.
  
  
  CONCLUSIONS
  The results of this study suggest that quercetagetin could be used in the functional food, cosmetic and pharmaceutical industries.
authors.affiliation: Department of Marine Life Science, Jeju National University, Jeju 690-756, Republic of South Korea.
authors.forename: Xiudong
authors.initials: X
authors.lastname: Yang
authors.forename: Sung-Myung
authors.initials: SM
authors.lastname: Kang
authors.forename: Byong-Tae
authors.initials: BT
authors.lastname: Jeon
authors.forename: Yong-Deog
authors.initials: YD
authors.lastname: Kim
authors.forename: Jin-Hwan
authors.initials: JH
authors.lastname: Ha
authors.forename: Yong-Tae
authors.initials: YT
authors.lastname: Kim
authors.forename: You-Jin
authors.initials: YJ
authors.lastname: Jeon
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D001713:Biphenyl Compounds / Q000378:metabolism; D002522:Chlorocebus aethiops; D002867:Chromones / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002957:Citrus / Q000737:chemistry*; D004249:DNA Damage; D047309:Flavones; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D005638:Fruit / Q000737:chemistry*; D006861:Hydrogen Peroxide; D017665:Hydroxyl Radical / Q000378:metabolism; D010851:Picrates / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D014709:Vero Cells; D014866:Waste Products
chemical_list: D000975:Antioxidants; D001713:Biphenyl Compounds; D002867:Chromones; D047309:Flavones; D005419:Flavonoids; D010851:Picrates; D010936:Plant Extracts; D017382:Reactive Oxygen Species; D014866:Waste Products; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; C004931:1,1-diphenyl-2-picrylhydrazyl; C079163:quercetagetin