Systematic study on active compounds as antibacterial and antibiofilm agent in aging onions

J Food Drug Anal. 2018 Apr;26(2):518-528. doi: 10.1016/j.jfda.2017.06.009. Epub 2017 Jul 26.


Quantitative investigation and systematic studies of quercetin, total phenolics, flavonoids, antioxidants, antibacterial and antibiofilm or antibiofouling properties of methanolic extracts of onions obtained from six different varieties have been carried out to explore their relative merits in terms of biological activities of fresh and aging onions. Total phenolic content in the extracts was examined spectrophotometrically using Folin-Ciocalteau's phenol reagent and total antioxidant activity was studied by FRAP and DPPH methods. In vitro antibacterial activity of the extracts was investigated on Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus and Bacillus cereus) respectively, by using a modified Kirby-Bauer disc diffusion method. Antibiofilm activity was tested by crystal violet assay. The best results against biofilm formation were observed for the extracts obtained from onions stored for three months. The total phenolic and antioxidant content found to be increased upon aging in all the six varieties; red skinned onion (Happyhong) showed the highest level of total phenolics (5110.07 ± 196.56 μg GAEg-1 FW) and total flavonoids (2254.00 ± 154.82 μg QEg-1 FW) after three months. The results showed that in all the varieties, quercetin content as well as biological activity increases with aging in the stored onions compared with the fresh ones.

Keywords: Antibacterial activity; Antioxidant activity; Deteriorated onion; Quercetin; Total phenolics.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / chemistry*
  • Anti-Bacterial Agents / pharmacology
  • Antioxidants / chemistry
  • Antioxidants / pharmacology
  • Biofilms / drug effects*
  • Microbial Sensitivity Tests
  • Onions / chemistry*
  • Phenols / chemistry
  • Phenols / pharmacology
  • Plant Extracts / chemistry*
  • Plant Extracts / pharmacology
  • Staphylococcus aureus / drug effects*
  • Staphylococcus aureus / physiology


  • Anti-Bacterial Agents
  • Antioxidants
  • Phenols
  • Plant Extracts

Grants and funding

This research was supported by the Nano Material Technology Development Program of the Korean National Research Foundation (NRF) funded by Korean Ministry of Education, Science, and Technology (2012M3A7B4049675). This work was also supported by the National Research Foundation of Korea (NRF) grant funded by Priority Research Centers Program (2014R1A6A1031189).