Related Experiment Video
Updated: Apr 19, 2026
Comparative Study on the Polysaccharide Contents and Antioxidant Activities of Hippophae rhamnoides subsp. sinensis and Hippophae gyantsensis
Published on: August 15, 2025
Structural analyses and immunomodulatory properties of fructo-oligosaccharides from onion (Allium cepa)
V Prasanna Kumar1, K V Harish Prashanth2, Y P Venkatesh1
1Department of Biochemistry and Nutrition, CSIR-Central Food Technological Research Institute (CFTRI), Mysore, Karnataka, India.
Abstract:
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.
Insights
Onion fructo-oligosaccharides (FOS) were isolated and characterized. These compounds demonstrated significant in vitro immunostimulatory effects on mouse lymphocytes and macrophages.
Area of Science:
- Food Science
- Immunology
- Carbohydrate Chemistry
Background:
- Onions (Allium cepa) are recognized for their health benefits, particularly their rich fructan content.
- Fructans, including fructo-oligosaccharides (FOS), are known to modulate the immune system.
- Understanding the specific immunomodulatory properties of onion-derived FOS is crucial for functional food development.
Purpose of the Study:
- To isolate and structurally characterize fructo-oligosaccharides (FOS) from onion bulbs.
- To investigate the in vitro immunomodulatory activities of onion FOS on immune cells.
Main Methods:
- Hot 80% ethanol extraction of FOS from onion bulbs, followed by gel permeation chromatography for purification.
- Structural analysis using Nuclear Magnetic Resonance (NMR), Thin-Layer Chromatography (TLC), and Electrospray Ionization Mass Spectrometry (ESI-MS).
- In vitro assays measuring lymphocyte proliferation, nitric oxide production, intracellular free radical production, and phagocytic activity of isolated immune cells.
Main Results:
- Onion FOS were successfully isolated with a yield of approximately 4.5 g/100 g fresh weight.
- Structural analysis revealed onion FOS as inulin-type fructans ranging from trisaccharides to hexasaccharides, with an unusual β-D-Glc terminal residue.
- Onion FOS significantly enhanced mouse splenocyte/thymocyte proliferation and augmented nitric oxide production, free radical scavenging, and phagocytic activity in murine peritoneal exudate cells.
Conclusions:
- Onion FOS, composed of tri- to hexasaccharide units, possess significant in vitro immunostimulatory properties.
- These findings highlight the potential of onion FOS as functional ingredients for immune system support.
- Further research into the in vivo effects and mechanisms of action of onion FOS is warranted.
