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.