title: Antioxidant activity of phenolic extracts from different cultivars of Italian onion (Allium cepa) and relative human immune cell proliferative induction.
abstract: BACKGROUND
  The total antioxidant activity (TAC) may vary considerably between onion cultivars. Immunological effects of onion phenolic compounds are still underestimated.
  
  
  OBJECTIVE
  The objective of this study is to determine the total phenol content (TPC) and the relative TAC of three Allium cepa L. (Liliaceae) onion cultivars cultivated in Cannara (Italy): Rossa di Toscana, Borettana di Rovato, and Dorata di Parma, and to evaluate the phenol extracts ability to induce human immune cell proliferation.
  
  
  METHODS
  TPC was determined by the Folin-Ciocalteu method, TAC with FRAP, TEAC/ABTS, and DPPH methods. Peripheral blood mononuclear cells from healthy human donors were incubated for 24 h at 37 °C with 1 ng/mL of phenolic extract in PBS, immunostained, and then analyzed by 4-color flow cytometry for the phenotypic characterization of T helper cells (CD4+ cells), cytotoxic T lymphocytes (CD8+ cells), T regulatory cells (CD25high CD4+ cells), and natural killer cells/monocytes (CD16+ cells).
  
  
  RESULTS
  Rossa di Toscana displayed the highest TPC (6.61 ± 0.87 mg GA equivalents/g onion bulb DW) and the highest TAC with the experienced methods: FRAP, 9.19 ± 2.54 μmol Trolox equivalents/g onion bulb DW; TEAC/ABTS, 21.31 ± 0.41 μmol Trolox equivalents/g onion bulb DW; DPPH, 22.90 ± 0.01 μmol Trolox equivalents/g onion bulb DW. Incubation with Rossa di Toscana extract determined an increase in the frequency of the antitumor/anti-infection NK CD16+ immune cells (23.0 ± 0.4%).
  
  
  CONCLUSIONS
  Content of health-promoting phenols and the deriving antioxidant and immunostimulating activity vary considerably among the investigated cultivars. Rossa di Toscana can be considered as a potential functional food.
authors.affiliation: a Department of Pharmaceutical Sciences , University of Perugia , Perugia , Italy and.
authors.forename: Antonella
authors.initials: A
authors.lastname: Lisanti
authors.affiliation: b Medical Oncology Unit, Tor Vergata University Hospital , Rome , Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Formica
authors.affiliation: a Department of Pharmaceutical Sciences , University of Perugia , Perugia , Italy and.
authors.forename: Federica
authors.initials: F
authors.lastname: Ianni
authors.affiliation: a Department of Pharmaceutical Sciences , University of Perugia , Perugia , Italy and.
authors.forename: Barbara
authors.initials: B
authors.lastname: Albertini
authors.affiliation: a Department of Pharmaceutical Sciences , University of Perugia , Perugia , Italy and.
authors.forename: Maura
authors.initials: M
authors.lastname: Marinozzi
authors.affiliation: a Department of Pharmaceutical Sciences , University of Perugia , Perugia , Italy and.
authors.forename: Roccaldo
authors.initials: R
authors.lastname: Sardella
authors.affiliation: a Department of Pharmaceutical Sciences , University of Perugia , Perugia , Italy and.
authors.forename: Benedetto
authors.initials: B
authors.lastname: Natalini
mesh_terms: D000975:Antioxidants / Q000302:isolation & purification / Q000494:pharmacology*; D049109:Cell Proliferation / Q000187:drug effects* / Q000502:physiology; D002478:Cells, Cultured; D006801:Humans; D007558:Italy; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000502:physiology; D019697:Onions; D010636:Phenols / Q000302:isolation & purification / Q000494:pharmacology*; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000502:physiology
chemical_list: D000975:Antioxidants; D010636:Phenols; D010936:Plant Extracts
keywords: Immunological effect; onion bulb extracts; total antioxidant capacity; total phenol content