Liquid and Vapor Phase of Four Conifer-Derived Essential Oils: Comparison of Chemical Compositions and Antimicrobial and Antioxidant Properties

Abstract

In this study, the chemical composition of the vapor and liquid phase of Pinus cembra L., Pinus mugo Turra, Picea abies L., and Abies Alba M. needles essential oils (EOs) was investigated by Headspace-Gas Chromatography/Mass Spectrometry (HS-GC/MS). In the examined EOs, a total of twenty-eight components were identified, most of which belong to the monoterpenes family. α-Pinene (16.6–44.0%), β-pinene (7.5–44.7%), limonene (9.5–32.5%), and γ-terpinene (0.3–19.7%) were the most abundant components of the liquid phase. Such major compounds were also detected in the vapor phase of all EOs, and α-pinene reached higher relative percentages than in the liquid phase. Then, both the liquid and vapor phases were evaluated in terms of antibacterial activity against three Gram-negative bacteria (Escherichia coli, Pseudomonas fluorescens, and Acinetobacter bohemicus) and two Gram-positive bacteria (Kocuria marina and Bacillus cereus) using a microwell dilution assay, disc diffusion assay, and vapor phase test. The lowest Minimum Inhibitory Concentration (MIC) (13.28 mg/mL) and Minimal Bactericidal Concentration (MBC) (26.56 mg/mL) values, which correspond to the highest antibacterial activities, were reported for P. abies EO against A. bohemicus and for A. alba EO against A. bohemicus and B. cereus. The vapor phase of all the tested EOs was more active than liquid phase, showing the inhibition halos from 41.00 ± 10.15 mm to 80.00 ± 0.00 mm for three bacterial strains (A. bohemicus, K. marina, and B. cereus). Furthermore, antioxidant activities were also investigated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis (3- ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) assays, and a concentration-dependent antioxidant capacity for all EOs was found. P. mugo EO showed the best antioxidant activity than the other Pinaceae EOs. The four Pinaceae EOs could be further investigated for their promising antibacterial and antioxidant properties, and, in particular, α-pinene seems to have interesting possibilities for use as a novel natural antibacterial agent.

Headspace/GC–MS Analysis and Investigation of Antibacterial, Antioxidant and Cytotoxic Activity of Essential Oils and Hydrolates from Rosmarinus officinalis L. and Lavandula angustifolia Miller

“…The Petri plates were sealed with parafilm in order to prevent any vapor leakage. After 24 h of incubation, the inhibition halo was measured by a vernier caliper rule [33]. The means and standard deviations were obtained by triplicate measures of the Agar disk-diffusion and VPT halos.…”

“…Their aroma can be more or less intense depending on their content of molecules that provide a potential biological effect, making the hydrolates useful for the food industry as preserving and/or aromatic agents [31]. In this study, for the first time, to better describe the vapor phase chemical profiles of Hys and EOs obtained from flowers and inflorescences of R. officinalis and inflorescences of L. angustifolia growing in Tuscany, we used the automated headspace sampler directly coupled with gas chromatography-mass spectrometry (HS/GC-MS) [32,33]. This sampling technique is conservative and non-destructive and does not require the use of solvent for the extraction process, thus avoiding a possible loss of components.…”

Chemical Composition of Fir, Pine and Thyme Essential Oils and Their Effect on Onion (Allium cepa L.) Seed Quality

“…The antimicrobial activity of fir and pine oils have been frequently reported as well, however, mostly with regard to bacteria and fungi pathogenic to humans. In the experiment of Garzoli et al [22], fir essential oil showed the highest antibacterial activity against Acinetobacter bohemicus and Bacillus cereus among four tested oils. Moreover, the authors observed that the vapor phase of all tested essential oils was more active than liquid phase.…”

Antioxidant and Antibacterial Properties of Norway Spruce (Picea abies H. Karst.) and Eastern Hemlock (Tsuga canadensis (L.) Carrière) Cone Extracts

“…Tanase et al [83] In a comparative study of the essential oils of four Pinus species, Mitic et al [86] observed that the sensitivity of the tested bacterial pathogens is related to the cell wall structure. Different mechanisms of action can explain the antimicrobial activities of cones, and their wide variety of molecular components can act at multiple levels [87]. Generally, Gram-negative bacteria are more resistant than Gram-positive bacteria because the cell wall does not allow entrance into the cell of hydrophobic molecules present in the cone extracts [88,89].…”