Structural analyses and immunomodulatory properties of fructo-oligosaccharides from onion (Allium cepa)

Carbohydr Polym. 2015 Mar 6;117:115-122. doi: 10.1016/j.carbpol.2014.09.039. Epub 2014 Sep 28.


Onion (Allium cepa) is an immune-boosting food rich in fructans. The major aim of this study is to characterize and investigate the immunomodulatory properties of onion fructo-oligosaccharides (FOS). FOS was isolated from onion bulbs by hot 80% ethanol extraction (yield: ∼4.5 g/100 g fw) followed by gel permeation chromatography. NMR of onion FOS revealed unusual β-D-Glc terminal residue at the non-reducing end. TLC and ESI-MS analyses showed that onion FOS ranged from trisaccharides to hexasaccharides. Onion FOS (50 μg/mL) significantly increased (∼3-fold) the proliferation of mouse splenocytes/thymocytes vs. control. Further, onion FOS enhanced (∼2.5-fold) the production of nitric oxide by peritoneal exudates cells (PECs) from Wistar rats; intracellular free radicals production and phagocytic activity of isolated murine PECs were also augmented. Our structural and in vitro results indicate that onion FOS comprising of tri- to hexasaccharide units belongs to inulin-type fructans, and possess immunostimulatory activities towards murine lymphocytes and macrophages.

Keywords: Fructo-oligosaccharides; Immunomodulation; Inulin; Mitogenicity; Onion; Phagocytosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Proliferation / drug effects
  • Ethanol / chemistry
  • Free Radicals / metabolism
  • Fructans / chemistry*
  • Fructans / isolation & purification
  • Fructans / pharmacology*
  • Immunologic Factors / chemistry*
  • Immunologic Factors / isolation & purification
  • Immunologic Factors / pharmacology*
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Lymphocytes / drug effects
  • Lymphocytes / immunology
  • Macrophages, Peritoneal / drug effects
  • Macrophages, Peritoneal / metabolism
  • Male
  • Mice
  • Nitric Oxide / metabolism
  • Oligosaccharides / chemistry*
  • Onions / chemistry*
  • Phagocytosis / drug effects
  • Rats
  • Spleen / cytology


  • Free Radicals
  • Fructans
  • Immunologic Factors
  • Oligosaccharides
  • Nitric Oxide
  • Ethanol