Chemical Composition, Antibacterial, Antibiofilm and Synergistic Properties of Essential Oils from Eucalyptus globulus Labill. and Seven Mediterranean Aromatic Plants

Abstract

Essential oils (EOs) from Eucalyptus globulus Labill. ssp. globulus and from Mediterranean autochthonous aromatic plants - Thymus mastichina L., Mentha pulegium L., Rosmarinus officinalis L., Calamintha nepeta (L.) Savi ssp. nepeta, Cistus ladanifer L., Foeniculum vulgare L., Dittrichia viscosa (L.) Greuter ssp. viscosa - were extracted by hydrodistillation and characterized by GC-FID and NMR spectroscopy. EOs were evaluated for antimicrobial properties against several bacterial strains, using diverse methods, namely, the agar disc-diffusion method, the microdilution method, the crystal violet assay and the Live/Dead staining for assessment of biofilm formation. Potential synergy was assessed by a checkerboard method. EOs of R. officinalis and C. ladanifer showed a predominance in monoterpene hydrocarbons (> 60%); EOs of C. nepeta, M. pulegium, T. mastichina, E. globulus and F. vulgare were rich in oxygenated monoterpenes (62 - 96%) whereas EO of D. viscosa was mainly composed of oxygenated sesquiterpenes (54%). All EOs showed antimicrobial activity; M. pulegium and E. globulus generally had the strongest antimicrobial activity. EO of C. nepeta was the most promising in hampering the biofilm formation. The combinations D. viscosa/C. nepeta and E. globulus/T. mastichina were synergistic against Staphylococcus aureus. These results support the notion that EOs from the aromatic plants herein reported should be further explored as potential pharmaceuticals and/or food preservatives.

Chemical Composition and in Vitro Cytotoxic Screening of Sixteen Commercial Essential Oils on Five Cancer Cell Lines

“…Zidane et al . and Vieira et al . found that Cis.la‐EO was rich in α ‐pinene and camphene while Gomes, Mata, and Rodrigues reported viridifloral and globulol as the major components.…”

Repellent, Insecticidal and Antimicrobial Activities of Leaf Essential Oils from Three Eucalyptus Species

“…Essential oils are complex mixtures of volatile organic substances, consisting of oxygenated compounds and hydrocarbons, such as sesquiterpenes and monoterpenes, were widely applied in food, perfumes, toiletries, chemical additives, medicine and pharmaceutical science . Many plant essential oils and their major constituents exhibit a wide range of biological properties, such as insecticidal, antibacterial, antifungal, spasmolytic, and so on . Due to the great value, the development of essential oils from plants and evaluation on their activities is still highly desirable.…”

Cistus ladanifer (Cistaceae): a natural resource in Mediterranean-type ecosystems

“…C. ladanifer shows a different terpene profile from other Cistus species, with a close taxonomic relationship (Gulz 1984;Oller-López et al 2005). Regarding mono-and sesquiterpenes, the most common reported major compounds are the monoterpenes α-pinene (Gomes et al 2005;Gulz 1984;Mariotti et al 1997;Rincón et al 2000;Robles et al 2003;Teixeira et al 2007;Vieira et al 2017), camphene (Zidane et al 2013) and pinocarveol (Oller-López et al 2005;Verdeguer et al 2012) and the sesquiterpene viridiflorol (Gomes et al 2005;Greche et al 2009;Weyerstahl et al 1998). In their literature review, Gomes et al (2005) also observed that α-pinene was the most commonly reported major compound.…”

“…Another important compound found in high proportions in C. ladanifer extracts is the carotenoid derivative norisoprene called 2,2,6-trimethylcyclohexanone (Gomes et al 2005;Greche et al 2009;Mariotti et al 1997;Oller-López et al 2005;Ramalho et al 1999;Robles et al 2003;Santos et al 2017;Teixeira et al 2007;Verdeguer et al 2012;Weyerstahl et al 1998;Zidane et al 2013), which is one Barros et al (2013); Chaves et al (1997aChaves et al ( , b, 1998Chaves et al ( , 2001); Fernández-Arroyo et al 2010; Guimarães et al (2009); Gomes et al (2005); Greche et al (2009); Gulz (1984); Mariotti et al (1997);Oller-López et al (2005); Pascual et al (1982); Proksch and Gulz (1980a, b); Ramalho et al (1999); Rincón et al (2000); Robles et al (2003); Santos et al (2017); Sosa et al (2004); Teixeira et al (2007); Verdeguer et al (2012); Vieira et al (2017); Vogt et al (1987); Weyerstahl et al (1998); Wollenweber and Mann (1984) Extracts (Gomes et al 2005;Greche et al 2009;Gulz 1984;Mariotti et al 1997;…”