Chemical Composition, In Vitro and In Situ Antimicrobial and Antibiofilm Activities of Syzygium aromaticum (Clove) Essential Oil

Abstract

The essential oil of <i>Syzygium</i> (<i>S.</i>) <i>aromaticum</i> (CEO) is known for its good biological activity. The aim of the research was to evaluate <i>in vitro</i> and <i>in situ</i> antimicrobial and antibiofilm activity of the essential oil produced in Slovakia. The main components of CEO were eugenol 82.4% and (E)-caryophyllene 14.0%. The antimicrobial activity was either weak or very strong with inhibition zones ranging from 4.67 to 15.78 mm in gram-positive and gram-negative bacteria and from 8.22 to 18.56 mm in yeasts and fungi. Among the tested bacteria and fungi, the lowest values of MIC were determined for <i>Staphylococcus</i> (<i>S.</i>) <i>aureus</i> and <i>Penicillium</i> (<i>P.</i>) <i>expansum</i>, respectively. The vapor phase of CEO inhibited the growth of the microscopic filamentous fungi of the genus <i>Penicillium</i> when tested <i>in situ</i> on bread. The strongest effect of mycelia inhibition in a bread model was observed against <i>P. expansum</i> at concentrations of 250 and 500 μL/mL. The best antimicrobial activity of CEO in the carrot model was found against <i>P. chrysosenum</i>. Differences between the mass spectra of <i>Bacillus</i> (<i>B.</i>) <i>subtilis</i> biofilms on the tested surfaces (wood, glass) and the control sample were noted from the seventh day of culture. There were some changes in mass spectra of <i>Stenotrophomonas</i> (<i>S.</i>) <i>maltophilia</i>, which were observed in both experimental groups from the fifth day of culture. These findings confirmed the impact of CEO on the protein structure of older biofilms. The findings indicate that, besides being safe and sensorially attractive, <i>S. aromaticum</i> has antimicrobial activity, which makes it a potential substitute for chemical food preservatives.