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.
Highlights
A few papers reporting the Pinaceae essential oils (EOs) chemical composition are present, and no report describes the volatile composition of the vapor phase of the conifer-derived EOs by HS-Gas Chromatography-Mass Spectrometry (GC/mass spectrometer (MS)), as we applied for our investigation
For the first time, the chemical composition of the liquid and vapor phase of four Pinaceae EOs was investigated by the HS-GC/MS technique
The results of analyses showed that these EOs are rich in monoterpenoids and highlight that α-pinene, one of the main compounds, is more abundant in the vapor phase of each oil than in the liquid phase
Summary
Plants are a source of different kinds of compounds that humans used for their numerous biological activities and as a source for drug development [1]. Numerous papers deal with the biological activities of the EOs such as antioxidant and anti-inflammatory properties, antibacterial and antifungal activities, immunomodulatory effects, and cytotoxic activities against different cancer cell lines [13,14,15,16,17,18,19]. Antioxidant, antibacterial, antifungal, insect larvicidal, anti-inflammatory, and antiproliferative activities are reported for different genus of the Pinaceae family [16,23,24,25,26,27,28,29,30]
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