Oleuropein Is Responsible for the Major Anti-Inflammatory Effects of Olive Leaf Extract

J Med Food. 2018 Mar;21(3):302-305. doi: 10.1089/jmf.2017.0070. Epub 2017 Nov 3.

Abstract

Olive leaves are rich in polyphenolic compounds that are known to have antioxidant, antimicrobial, and anti-inflammatory activities. Therefore, olive leaf extract (OLE) is considered as a natural supplement. In this study we evaluated the antibacterial and the anti-inflammatory effect of OLE and its individual phenolic components in vitro. Polymorphonuclear cells (PMNCs) were isolated from the whole blood using Histopaque solution and cultured in RPMI-enriched medium. Tumor necrosis factor α (TNFα) level was determined by ELISA after 24 h of lipopolysaccharide stimulation. The antibacterial activity of OLE was determined by well diffusion assay. We found a significant decrease in TNFα secretion level in PMNCs culture treated with OLE. Oleuropein is the only OLE component that has shown anti-inflammatory effects at a concentration of 20 μg/mL. Furthermore, OLE exhibited antibacterial activity against some gram positive bacterial strains; however, gram negative bacterial strains were resistant to OLE. Downregulation of TNFα secretion in PMNCs culture in response to OLE treatment indicates that this polyphenol-rich extract has an anti-inflammatory effect, and oleuropein is the major OLE component responsible for this effect. The antibacterial activity of OLE is limited to gram positive bacteria.

Keywords: OLE; TNFα; gallic acid; oleuropein; olive leaf extract; phenolic compounds.

MeSH terms

  • Anti-Bacterial Agents / analysis
  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / pharmacology
  • Anti-Inflammatory Agents, Non-Steroidal / adverse effects
  • Anti-Inflammatory Agents, Non-Steroidal / analysis
  • Anti-Inflammatory Agents, Non-Steroidal / chemistry
  • Anti-Inflammatory Agents, Non-Steroidal / pharmacology*
  • Cell Survival / drug effects
  • Cells, Cultured
  • Dietary Supplements / adverse effects
  • Dietary Supplements / analysis*
  • Disk Diffusion Antimicrobial Tests
  • Drug Resistance, Bacterial
  • Escherichia coli / drug effects
  • Escherichia coli / growth & development
  • Food Preservatives / adverse effects
  • Food Preservatives / analysis
  • Food Preservatives / chemistry
  • Food Preservatives / pharmacology
  • Humans
  • Iridoids / adverse effects
  • Iridoids / analysis
  • Iridoids / pharmacology*
  • Lipopolysaccharides / toxicity
  • Neutrophils / cytology
  • Neutrophils / drug effects*
  • Neutrophils / immunology
  • Neutrophils / metabolism
  • Olea / chemistry*
  • Osmolar Concentration
  • Plant Extracts / adverse effects
  • Plant Extracts / chemistry
  • Plant Extracts / pharmacology*
  • Plant Leaves / chemistry*
  • Pseudomonas aeruginosa / drug effects
  • Pseudomonas aeruginosa / growth & development
  • Staphylococcus / drug effects
  • Staphylococcus / growth & development
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Anti-Bacterial Agents
  • Anti-Inflammatory Agents, Non-Steroidal
  • Food Preservatives
  • Iridoids
  • Lipopolysaccharides
  • Plant Extracts
  • TNF protein, human
  • Tumor Necrosis Factor-alpha
  • oleuropein