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Open AccessArticle

Anti-Haemophilus Activity of Selected Essential Oils Detected by TLC-Direct Bioautography and Biofilm Inhibition

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Department of Pharmacognosy, Faculty of Pharmacy, University of Pécs, H-7624 Pécs, Hungary
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Institute of Pharmaceutical Technology and Biopharmacy, Faculty of Pharmacy, University of Pécs, H-7624 Pécs, Hungary
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Department of Microbiology, Faculty of Science and Informatics, University of Szeged, H-6726 Szeged, Hungary
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Department of Medical Microbiology and Immunology, Medical School, University of Pécs, H-7624 Pécs, Hungary
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Institute of Pharmacognosy, Faculty of Pharmacy, Semmelweis University, H-1085 Budapest, Hungary
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Department of Genetics and Molecular Biology, Institute of Biology, Faculty of Sciences, University of Pécs, H-7624 Pécs, Hungary
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Department of Food Engineering, Faculty of Engineering, University of Szeged, H-6724 Szeged, Hungary
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Author to whom correspondence should be addressed.
Molecules 2019, 24(18), 3301; https://doi.org/10.3390/molecules24183301
Received: 7 August 2019 / Revised: 5 September 2019 / Accepted: 10 September 2019 / Published: 11 September 2019
(This article belongs to the Section Natural Products Chemistry)
Essential oils (EOs) are becoming increasingly popular in medical applications because of their antimicrobial effect. Direct bioautography (DB) combined with thin layer chromatography (TLC) is a screening method for the detection of antimicrobial compounds in plant extracts, for example, in EOs. Due to their lipophilic character, the common microbiological assays (etc. disk diffusion) could not provide reliable results. The aim of this study was the evaluation of antibacterial and anti-biofilm properties of the EO of cinnamon bark, clove, peppermint, thyme, and their main components against Haemophilus influenzae and H. parainfluenzae. Oil in water (O/W) type Pickering nano-emulsions stabilized with silica nanoparticles from each oil were prepared to increase their water-solubility. Samples with Tween80 surfactant and absolute ethanol were also used. Results showed that H. influenzae was more sensitive to the EOs than H. parainfluenzae (except for cinnamon bark oil). In thin layer chromatography-direct bioautography (TLC-DB) the ethanolic solutions of thyme oil presented the best activity against H. influenzae, while cinnamon oil was the most active against H. parainfluenzae. Pickering nano-emulsion of cinnamon oil inhibited the biofilm formation of H. parainfluenzae (76.35%) more efficiently than samples with Tween80 surfactant or absolute ethanol. In conclusion, Pickering nano-emulsion of EOs could inhibit the biofilm production effectively. View Full-Text
Keywords: essential oil; clove; thyme; cinnamon bark; peppermint; anti-biofilm activity; Pickering nano-emulsion; Haemophilus influenzae; Haemophilus parainfluenzae essential oil; clove; thyme; cinnamon bark; peppermint; anti-biofilm activity; Pickering nano-emulsion; Haemophilus influenzae; Haemophilus parainfluenzae
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Balázs, V.L.; Horváth, B.; Kerekes, E.; Ács, K.; Kocsis, B.; Varga, A.; Böszörményi, A.; Nagy, D.U.; Krisch, J.; Széchenyi, A.; Horváth, G. Anti-Haemophilus Activity of Selected Essential Oils Detected by TLC-Direct Bioautography and Biofilm Inhibition. Molecules 2019, 24, 3301.

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