Plant Phenols as Antibiotic Boosters: In Vitro Interaction of Olive Leaf Phenols with Ampicillin

Abstract

The antimicrobial properties of olive leaf extract (OLE) have been well recognized in the Mediterranean traditional medicine. Few studies have investigated the antimicrobial properties of OLE. In this preliminary study, commercial OLE and its major phenolic secondary metabolites were evaluated in vitro for their antimicrobial activities against Escherichia coli and Staphylococcus aureus, both individually and in combination with ampicillin. Besides luteolin 7-O-glucoside, OLE and its major phenolic secondary metabolites were effective against both bacteria, with more activity on S. aureus. In combination with ampicillin, OLE, caffeic acid, verbascoside and oleuropein showed additive effects. Synergistic interaction was observed between ampicillin and hydroxytyrosol. The phenolic composition of OLE and the stability of olive phenols in assay medium were also investigated. While OLE and its phenolic secondary metabolites may not be potent enough as stand-alone antimicrobials, their abilities to boost the activity of co-administered antibiotics constitute an imperative future research area.

RETRACTED: CuO and CeO2 Nanostructures Green Synthesized Using Olive Leaf Extract Inhibits the Growth of Highly Virulent Multidrug Resistant Bacteria

“…The abundance of oleuropein over other phenolic compounds was observed in HPLC chromatogram of olive leaf extract ( Figure 2 ), as reported in previous studies ( Lim et al, 2016 ; Maalej et al, 2017 ). Oleuropein is highly unstable molecule and will rapidly breakdown into more polarizable hydroxytyrosol (C 8 H 10 O 3 ) usually in organic solvents ( Maqbool et al, 2016 ).…”

“…Due to the divergent physio-chemical characteristics of Cu and Ce, both of them have shown differential inhibitory behavior. Phyto-reductants from olive leaf extract have also shown mild inhibitory actions and these bactericidal properties of olive plant extract are well known in literature ( Lim et al, 2016 ; Maalej et al, 2017 ).…”

“…Olive leaf aqueous extract contains a variety of phyto-reductants for tailoring NS. The biomedical potential of olive is well known primarily due to the presence of antioxidants like oleuropein, oleuroside and apigenin-7-O-glucoside ( Lim et al, 2016 ; Maalej et al, 2017 ; Marslin et al, 2018 ).…”

The Potential of Systems Biology to Discover Antibacterial Mechanisms of Plant Phenolics

“…Synergistic effects have already been observed for many phenolic compounds when combined with antibiotics currently in use (reviewed by Aiyegoro and Okoh, 2009; Hemaiswarya and Doble, 2010; Amin et al, 2015; essential oil components reviewed by Langeveld et al, 2014; Oh and Jeon, 2015; Lim et al, 2016). Many synergistic effects have been attributed to membrane-disrupting compounds, including phenolics, which allow intracellular toxins faster/easier access to their targets (Hemaiswarya and Doble, 2010; Amin et al, 2015; Oh and Jeon, 2015).…”

Relationship between Adaptive Changing of Lysophosphatidylethanolamine Content in the Bacterial Envelope and Ampicillin Sensitivity of <b><i>Yersinia pseudotuberculosis</i></b>

“…A new aspect of plant polyphenols usefulness may be their synergistic or additive effects in combination with antibiotics [Lim et al, 2016]. However, the mechanism of plant polyphenols action is not yet clear.…”