Chemical Composition and Biological Activities of the Essential Oils of Leptospermum petersonii and Eucalyptus gunnii Article Swipe
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· 2020
· Open Access
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· DOI: https://doi.org/10.3389/fmicb.2020.00409
· OA: W3016998420
The aim of this study was to characterize the chemical composition and to evaluate the antimicrobial and phytotoxic properties of the essential oils (EOs) obtained from leaves of <i>Leptospermum petersonii</i> chemotype "Variety B" and <i>Eucalyptus gunnii</i>, native to Australia. Geranyl acetate, γ-terpinene, geraniol, terpinolene, α-pinene, <i>p</i>-cimene, and linalool were the main components in <i>L. petersonii</i> EO, confirming also the existence of several chemotypes in such taxa; on the other hand, 1,8-cineole, <i>trans</i>-sabinene hydrate acetate, globulol, longicyclene, terpinolene, and camphene were present in major amounts in the <i>E. gunnii</i> EO. Chemical analysis of <i>L. petersonii</i> revealed that it belongs to the variety "B." <i>E. gunnii</i> EO showed good antibacterial activity, with an MIC of 0.5 and 2 μg/mL against <i>Staphylococcus aureus</i>, and <i>Pectobacterium carotovorum</i>, respectively. The activity of <i>E. gunnii</i> EO was stronger than <i>L. petersonii</i> EO, whose maximum MIC reached 5 μg/mL. <i>E. gunnii</i> and <i>L. petersonii</i> EOs were particularly effective in inhibiting the biofilm formation by <i>S. aureus</i>, already at a concentration of 0.01 μg/mL. The other strains were resistant to both EOs up to a dose of 0.05 μg/mL. The maximum inhibition on biofilm formed by <i>P. carotovorum</i> was recorded for <i>E. gunnii</i> EO, reaching a value of 93.12% at 1.0 μg/mL. This is the first manuscript which studies the biofilm inhibition by EOs and evaluates their effects on biofilm metabolism. Both EOs were more effective against <i>P. carotovorum</i>. In addition, even though <i>L. petersonii</i> EO 0.1 μg/mL was unable to inhibit biofilm formation by <i>Escherichia coli</i>, it decreased the metabolic activity of the biofilm to 78.55% compared to control; furthermore, despite it inducing a relatively low inhibition (66.67%) on biofilm formation, it markedly affected metabolic activity, which decreased to 16.09% with respect to the control. On the contrary, <i>L. petersonii</i> EO 0.5 μg/mL induced a 79.88% inhibition of <i>S. aureus</i> biofilm, maintaining a high metabolic activity (90.89%) compared to the control. Moreover, this EO showed inhibitory activity against radical elongation of <i>Solanum lycopersicum</i> and the germination of radish. On the contrary, <i>E. gunnii</i> EO showed no phytotoxic activity.
