Olive leaf extract is characterized by a high content of polyphenols (oleuropein, hydroxytyrosol and their derivatives), which is associated with its therapeutic properties. The objective of the present research was to evaluate the antifungal activity of olive leaf extract against Candida albicans ATCC 10231 and C. dubliniensis CBS 7987 strains. Minimum inhibitory concentrations (MIC) of the extract were determined by several in vitro assays. The extract showed a concentration depended effect on the viability of C. albicans with MIC value of 46.875 mg mL-1 and C. dubliniensis with MIC value 62.5 mg mL-1. Most sensitive methods for testing the antifungal effect of the extracts were the trypan blue exclusion method and fluorescent dye exclusion method while MIC could not be determined by the method according to the EUCAST recommendation suggesting that herbal preparations contain compounds that may interfere with this susceptibility testing. The fluorescent dye exclusion method was also used for the assessment of morphological changes in the nuclei of treated cells. According to the obtained results, olive leaf extract is less effective against the tested strains than hydroxytyrosol, an olive plant constituent tested in our previous study.
1. E. Medina, M. Brenes, C. Romero, A. García and A. De Castro, Main antimicrobial compounds in table olives, J. Agric. Food Chem. 55 (2007) 9817-9823.
2. Y. Khan, P. Siddharth, V. Niraj, B. Amee and K. Vimal, Olea europaea: A phyto-pharmacological review, Pharmacol. Rev. 1 (2007) 114-118.
3. F. Ortega-Garcia and J. Peragon, HPLC analysis of oleuropein, hydroxytyrosol and tyrosol in stems and roots of Olea europaea L. cv. picual during ripening, J. Sci. Food Agr. 90 (2010) 2295-2300; DOI: 10.1002/jsfa.4085.
4. G. Ciafardini and B. A. Zullo, Microbiological activity in stored olive oil, Int. J. Food Microbiol. 75 (2002) 111-118.
5. T. Perrinjaquet-Moccetti, A. Busjahn, C. Schmidlin, A. Schmidt, B. Bradl and C. Aydogan, Food supplementation with an olive (Olea europaea L.) leaf extract reduces blood pressure in borderline hypertensive monozygotic twins, Phytother. Res. 22 (2008) 1239-1242; DOI: 10.1002/ptr.2455.
6. S. Bulotta, R. Corradino and M. Celano, Antiproliferative and antioxidant effects on breast cancer cells of oleuropein and its semisynthetetic peracetylated derivatives, Food Chem. 127 (2011) 1609-1614; DOI: 10.1016/j.foodchem.2011.02.025.
7. S. H. Omar, Oleuropein in olive and its pharmacological effects, Sci. Pharm. 78 (2010) 133-154; DOI: 10.3797/scipharm.0912-18.
8. A. N. Sudjana, C. D`Orazio, V. Ryan, N. Rasool, J. Ng, N. Islam, T. V. Riley and K. A. Hammer, Antimicrobial activity of commercial Olea europaea (olive) leaf extract, Int. J. Antimicrob. Ag. 33 (2009) 461-463; DOI: 10.1016/j.ijantimicag.2008.10.026.
9. M. T. Khayyal, M. A. El-Ghazaly, D. M. Abdallah, N. N. Nassar, S. N. Okpanyi and M. H. Kreuter, Blood pressure lowering effect of an olive leaf extract (Olea europea) in L-NAME induced hypertension in rats, Arznemittelforsch. 52 (2002) 797-802.
10. E. Susalit, N. Agus, I. Effendi, R. R. Tjandrawinata, D. Nofiarny, T. Perrinjaquet-Moccetti and M. Verbruggen, Olive (Olea europaea) leaf extract effective in patients with stage-1 hypertension: Comparison with captopril, Phytomedicine 18 (2011) 251-258; DOI: 10.1016/j.phymed. 2010.08.016.
11. R. Fabiani, P. Rosignoli, A. De Bartolomeo, R. Fuccelli, M. Servili, G. F. Montedoro and G. Morozzi, Oxidative DNA damage is prevented by extracts of olive oil, hydroxytyrosol, and other olive phenolic compounds in human blood mononuclear cells and HL60 cells, J. Nutr. 138 (2008) 1411-1416.
12. J. Anter, Z. Fernandez-Bedmar, M. Villatoro-Pulido, S. Demyda-Peyras, M. Moreno-Millán, A. Alonso-Moraga, A. Munoz-Serrano and M. D. Luque de Castro, A pilot study on the DNA-protective, cytotoxic, and apoptosis-inducing properties of olive-leaf-extracts, Mutat. Res. 723 (2011) 165-170; DOI: 10.1016/j.mrgentox.2011.05.005.
13. B. Le Tutour and D. Guedon, Antioxidative activities of Olea europaea leaves and related phenolic compounds, Phytochemistry 31 (1992) 1173-1178; DOI: 10.1016/0031-9422(92)80255-D.
14. A. P. Pereira, I. C. F. R. Ferreira, F. Marcelino, P. Valentão, P. B. Andrade, R. Seabra, L. Estevinho, A. Bento and J. A. Pereira, Phenolic compounds and antimicrobial activity of olive (Olea europaea L. cv. cobrancosa) leaves, Molecules 12 (2007) 1153-1162; DOI: 10.3390/12051153.
15. G. Bisignano, A. Tomaino, R. Lo Cascio, G. Crisafi, N. Uccella and A. Saija, On the in-vitro antimicrobial activity of oleuropein and hydroxytyrosol, J. Pharm. Pharmacol. 51 (1999) 971-974.
16. N. Caturla, L. Perez-Fons, A. Estepa and V. Micol, Differential effects of oleuropein, a biophenol from Olea europaea, on ionic and zwitterionic phospholipid model membranes, Chem. Phys. Lipids 137 (2005) 2-17.
17. D. Markin, L. Duek and I. Berdicevsky, In vitro antimicrobial activity of olive leaves, Mycoses 46 (2003) 132-136, DOI: 10.1046/j.1439-0507.2003.00859.x.
18. O. H. Lee and B. Y. Lee, Antioxidant and antimicrobial activities of individual and combined phenolics in Olea europaea leaf extract, Bioresour. Technol. 101 (2010) 3751-3754; DOI: 10.1016/j.biortech.2009.12.052.
19. N. Zorić, I. Horvat, N. Kopjar, A. Vučemilović, D. Kremer, S. Tomić and I. Kosalec, Hydroxytyrosol expresses antifungal activity in vitro, Curr. Drug Targets. 14 (2013) 992-998.
20. IOOC - International Olive Oil Council COI/T.20/Doc.29 - Determination of biophenols in olive oils by HPLC, 2009; http://www.internationaloliveoil.org/web/aa-ingles/corp/AreasActivitie/economics/ Areas Activitie.html; access date May 15, 2009.
21. EUCAST DEFINITIVE DOCUMENT EDef 7.2. Method for the determination of broth dilution minimum inhibitory concentrations of antifungal agents for yeasts, March 2012; http://www.eucast.org/fileadmin/src/media/PDFs/EUCAST_files/AFST/EUCAST_EDef_7_2_revision.pdf; access date April 15, 2014.
22. A. Klančnik, S. Piskernik, B. Jeršek and S. Smole Možina, Evaluation of diffusion and dilution methods to determine the antibacterial activity of plant extracts, J. Microbiol. Meth. 81 (2010) 121-126; DOI: 10.1016/j.mimet.2010.02.004.
23. T. Mosmann, Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays, J. Immunol. Methods 65 (1983) 55-63.
24. L. Karygianni, M. Cecere, A. L. Skaltsounis, A. Argyropoulou, E. Hellwig, N. Aligiannis, A. Wittmer and A. Al-Ahmad, High level antimicrobial efficacy of representative mediterranean natural plant extracts against oral microorganisms, Biomed. Res. Int. 2014 (2014) 1-8; DOI: 10.1155/2014/839019.
25. M. H. Halawi, S. M. Abdel Rahman and H. Yusef, Comparative study of the antifungal activity of Olea europaea L. Against some pathogenic Candida albicans isolates in Lebanon, Int. J. Curr. Microbiol. AppSci. 4 (2015) 970-984.
26. I. Kosalec, O. Puel, M. Delaforge, N. Kopjar, R. Antolović, D. Jelić, B. Matica, P. Galtier and S. Pepeljnjak, Isolation and cytotoxicity of low-molecular-weight metabolites of Candida albicans, Front. Biosci. 13 (2008) 6893-6904.