title: Evaluation of anti-oxidant activity and identification of major polyphenolics of the invasive weed Oxalis pes-caprae.
abstract: BACKGROUND
  Phytochemical analyses of weeds, many of which have been used in traditional medicine worldwide, could lead to the identification of secondary metabolites with significant biological activity.
  
  
  OBJECTIVE
  To perform an assessment of the chemical composition and exploitation potential of the invasive weed Oxalis pes-caprae. To evaluate the anti-oxidant activity of its extracts and isolate and characterise polyphenolic metabolites using LC-DAD-MS (ESI+) and NMR methods.
  
  
  METHODS
  Aerial parts of the invasive weed O. pes-caprae were extracted with solvents of increasing polarity and their major polyphenolic metabolites were identified by LC-DAD-MS (ESI+). The total phenolic content of the extracts was determined using the Folin-Ciocalteu method, while their anti-oxidant activity was evaluated on the basis of their ability to scavenge the stable free radical 1,1-diphenyl-2-picrylhydrazyl and hydrogen peroxide.
  
  
  RESULTS
  The major polyphenolic constituents of the extracts were tentatively characterised as chlorogenic acid, quinic ferulate, luteolin glucoside and cernuoside according to their MS and UV spectroscopic data. Cernuoside, an aureusidin glucoside, was isolated from the methanolic extract of the weed's flowers and its structure was unambiguously identified by 1D- and 2D-NMR spectroscopy. The butanol extract of O. pes-caprae displayed the highest anti-oxidant activity.
  
  
  CONCLUSIONS
  The metabolic profile of O. pes-caprae was studied and the structures of the major polyphenolic metabolites based on their MS and UV-vis spectra were tentatively assigned. The aureusidin glucoside cernuoside was isolated and characterised for the first time from O. pes-caprae. The extracts exhibited high levels of anti-oxidant activity.
authors.affiliation: Department of Food Quality and Chemistry of Natural Products, Mediterranean Agronomic Institute of Chania/ Centre International de Hautes Etudes Agronomiques Méditerranéennes, 73100, Chania, Crete, Greece.
authors.forename: Ilknur
authors.initials: I
authors.lastname: Güçlütürk
authors.forename: Anastasia
authors.initials: A
authors.lastname: Detsi
authors.forename: Erika Krisztina
authors.initials: EK
authors.lastname: Weiss
authors.forename: Efstathia
authors.initials: E
authors.lastname: Ioannou
authors.forename: Vassilios
authors.initials: V
authors.lastname: Roussis
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Kefalas
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002726:Chlorogenic Acid / Q000032:analysis; D002853:Chromatography, Liquid; D004353:Drug Evaluation, Preclinical; D006027:Glycosides / Q000032:analysis / Q000737:chemistry; D047311:Luteolin / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D019684:Magnoliopsida / Q000737:chemistry*; D009828:Oleanolic Acid / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D035261:Plant Components, Aerial / Q000737:chemistry; D010936:Plant Extracts / Q000494:pharmacology; D057685:Plant Weeds / Q000737:chemistry; D059808:Polyphenols / Q000032:analysis / Q000494:pharmacology*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000975:Antioxidants; D006027:Glycosides; D010936:Plant Extracts; D059808:Polyphenols; C406770:cernuoside A; D002726:Chlorogenic Acid; D009828:Oleanolic Acid; D047311:Luteolin