Antioxidant activity and protective effect of the outer scales hydroalcoholic extract of Allium cepa L. var. Tropea on toxicity damage induced by Cadmium in Caco-2 cells

Food Chem Toxicol. 2022 Dec:170:113495. doi: 10.1016/j.fct.2022.113495. Epub 2022 Oct 22.


The characterization of bioactive metabolites and the protective effects against Cadmium (Cd) of the hydroalcoholic extract from Allium cepa var. Tropea (Tropea red onion) in human Caco-2 colon adenocarcinoma cells and in vitro antioxidant effects were investigated. Tropea red onion extract showed high levels of bioactive compounds and a strong activity as radical scavenger and inhibitor of lipid peroxidation. The most abundant specialized metabolites were quercetin derivatives. In addition, the extract inhibited NO release in a dose-dependent manner. Exposure of Cd treated human Caco-2 cells to the Tropea red onion extract resulted in a higher cytoprotection with a significant falloff of cells damage produced by Cd. The effect of Tropea red onion evaluated with the MTT assay and LDH test, was time-dependent and more evident after 24h of treatment. Caco-2 cells treated with the Tropea red onion extract and CdCl2 at 24h showed a significant cytoprotection at concentrations equal to 50 μg/mL + 25 μM and 100 μg/mL + 25 μM while at 72h at a concentration of 25 μg/mL + 25 μM. We observed with MTT and LDH assays that treatment of cells with Tropea red onion extract at 24h was able to significantly prevent Cd-induced cytotoxicity alone.

Keywords: Cadmium; Human adenocarcinoma; Lipid peroxidation; Quercetin derivatives; Radical scavenging; Tropea red onion.

MeSH terms

  • Adenocarcinoma*
  • Antioxidants / metabolism
  • Antioxidants / pharmacology
  • Caco-2 Cells
  • Cadmium / metabolism
  • Cadmium / toxicity
  • Colonic Neoplasms*
  • Humans
  • Onions
  • Plant Extracts / metabolism
  • Plant Extracts / pharmacology


  • Antioxidants
  • Cadmium
  • Plant Extracts