Fermentation enhances the biological activity of Allium cepa bulb extracts

Area of Science:

• Food Science
• Biochemistry
• Microbiology

Background:

• Onion (Allium cepa) is recognized for its health benefits, often attributed to its flavonoid content.
• Traditional processing and fermentation can alter the phytochemical profile and bioactivity of plant-based foods.
• Understanding these changes is crucial for developing functional foods and nutraceuticals.

Purpose of the Study:

• To compare the chemical profiles and biological activities of aqueous, methanol, and fermented aqueous onion extracts.
• To investigate the role of fermentation in enhancing the bioactivity of onion compounds.
• To identify potential bioactive metabolites generated during lactic acid fermentation of onions.

Main Methods:

• High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD), Liquid Chromatography-Mass Spectrometry (LC-MS), and Gas Chromatography-Mass Spectrometry (GC-MS) for chemical characterization.
• Agar disk diffusion and bacterial growth kinetics assays for antibacterial activity.
• Comet assay, cell cycle distribution analysis, and cell viability testing for antigenotoxic and antiproliferative effects.

Main Results:

• Aqueous and methanolic onion extracts exhibited characteristic flavonol profiles but limited bioactivity.
• The fermented aqueous extract, lacking typical onion flavonoids, displayed significant antibacterial, antigenotoxic, and antiproliferative activities.
• Metabolites formed during lactic acid fermentation were identified as the primary drivers of enhanced bioactivity.

Conclusions:

• Lactic acid fermentation transforms onion compounds into metabolites with markedly enhanced bioactivity.
• Fermented onion extract represents a promising source of functional ingredients with potential health benefits.
• Metabolites, rather than precursor flavonoids, may be responsible for the observed biological effects of fermented onion.