Pro-/antioxidant and antibacterial activity of olive leaf extracts according to bioavailability of phenolic compounds
The olive leaf extract (OLE) is an aqueous extract from dried olive leaves which contains high amount of phytochemicals with biological activities. The aim of this work was to study the changes in phenolic compounds content, antibacterial and antioxidant activity of the OLE after an in vitro gastrointestinal process in presence of intestinal microorganisms. In addition, the matrix effect of major individual phenolic compounds was evaluated. The OLE individual phenolic compounds quantification was determined by HPLC. The OLE contained different phenolic compounds, such as hydroxytyrosol, oleuropein and tyrosol and after digestion, these amount bioavailable detected decreased. Additionally, the antibacterial and antioxidant activity of the extract was also significantly reduced after gastrointestinal digestion. Individual phenolic compounds of OLE showed a high antimicrobial activity against pathogenic bacteria and these showed a synergic and matrix effect in extract. Besides, these compounds showed a concentration-depend pro-/anti-oxidant activity. Therefore, although the extract is rich in phenolic compounds, the levels of these were reduced along digestion process advances, and also their antioxidant and antibacterial activity. In addition, the pro-/anti-oxidant activity shown by the extract and its major phenolic compounds must be delved into, as this may or may not be convenient depending on the future application of the extract.
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