Abstract
Atriplex semibaccata R.Br. is a perennial halophyte that has received much attention for studies of revegetation of marginal lands in arid and semi-arid environments. It was, recently, demonstrated that there are no risks in terms of contamination of essential oil (EO) from growing plant on such land. Interest in exploring the antibacterial and antioxidant potential of A. semibaccata EO has consequently been renewed. The objective of this study was to investigate the chemical composition, as well as the antioxidant and antibacterial activities of A. semibaccata EO. The antibacterial activity was evaluated against native (drug-sensitive) and multidrug-resistant (MDR) bacteria by testing the EO alone and in combination with conventional antibiotics. The chemical composition of EO was analyzed by gas chromatography/mass spectrometry, 52 chemical compounds were identified, and 2-Methoxy-4-vinyl phenol (48.9%), benzaldehyde (6.7%), and benzyl alcohol (6.3%) were found to be the main constituents of EO. Furthermore, the antioxidant activity was evaluated using a 2,2-diphenyl-1-picrylhydrazyl reducing–scavenging test. The EO from this species possessed high antioxidant activity (938.65 μg TE/g EO). The antibacterial test demonstrated an inhibitory effect on six native and MDR bacterial strains. We found that Staphylococcus aureus (Gram+), Klebsiella pneumoniae (Gram−), and Escherichia coli (Gram−) were more sensitive than MDR strains, with an inhibition zone ranging from 11.16 mm to 12 mm. Moreover, the minimum inhibitory concentration ranged from 3.12 mg/mL to 6.25 mg/mL. The combination of gentamicin and EO revealed a high synergistic effect. The effect on S. aureus and K. pneumoniae showed lower fractional inhibitory concentration indices of 0.39 and 0.27, respectively. The results also revealed that A. semibaccata EO contained compounds with antibacterial potential against MDR bacteria, with antioxidant properties, and with a moderate synergistic effect in combination with gentamicin. The EO from A. semibaccata could be considered a new and potential source of natural antioxidant and antibacterial agents. These findings make A. semibaccata an excellent choice for the revegetation of marginal lands with the subsequent use of biomass for the production of EO with significant potential in the control of microbial infection.
Highlights
The exploitation of marginal and saline land to produce useful biomass has attracted interest worldwide [1,2,3,4]
The present study demonstrates promising results since the Minimal Inhibitory Concentration (MIC) values were found to be equal to the Minimal Bactericidal Concentration (MBC) values, indicating a bactericidal effect on both native and methicillinresistant S. aureus and K. pneumoniae, and native E. coli (ATCC 25922)
The present study demonstrated that the interaction between the essential oil (EO) of A. semibaccata and a standard antibiotic was notably effective using lower doses (MIC/4)
Summary
The exploitation of marginal and saline land to produce useful biomass has attracted interest worldwide [1,2,3,4]. Plant species with valuable biomass in terms of bioenergy, biomaterials, and essential oil (EO) production may play a primary role in the revegetation of these lands, providing environmental and socioeconomic benefits [5,6,7]. Species Atriplex L. genus have been recommended for the restoration of saline and marginal lands [8]. A. portulacoides L., and others [13,14]. Interest in these species is currently increasing due to their eminent content of bioactive compounds [14], such as A
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