Phytochemical composition and antimicrobial, antioxidant, anti-quorum sensing, and antibiofilm activities of essential oil blends used in aromatherapy

Introduction

The present study aimed to investigate the chemical compositions of two commercial EO blends (EOBls: A and B) used in aromatherapy, named “Abundance oil”, by gas chromatography-mass spectrometry (GCMS–) and to compare their antioxidant, antimicrobial, antibiofilm, and anti-quorum sensing (QS) potentials.

Methods

The radical scavenging activities of EOBls were performed by DPPH and ABTS^●+assays. Agar well diffusion and broth microdilution assays were also performed to evaluate their antimicrobial activity. Quorum sensing (QS) inhibition of EOBls was assessed by the biosensor strains Chromobacterium violaceum ATCC 12,472 and Pseudomonas aeruginosa PAO1. Biofilm inhibition assay was also performed using crystal violet.

Results

The GC–MS analysis of EOBl-A and EOBl-B presented the main constituents of limonene (53.18 %) and α-phellandrene (71.49 %), respectively. In antioxidant assays, EOBl-A, with high phenolic content, exhibited higher DPPH and ABTS^●+ radical scavenging effects than EOBl-B and the standard BHT. In antimicrobial activity, EOBls inhibited the growth of all strains in the range of 0.390 %-0.012 % (v/v), and the MIC values of EOBls were the lowest for Candida species (0.048 %-0.012 %v/v). In addition, EOBl-A and EOBl-B at MIC/2-MIC/32 significantly inhibited (p < 0.05) the violacein production, and EOBls at MIC, MIC/2, and MIC/4 exhibited concentration-dependent antibiofilm activity on all the strains.

Conclusion

The results revealed that EOBls could be candidates for antioxidant, antimicrobial, and anti-QS agents. Despite their remarkable pharmacological activities, further studies of EOBls should investigate their therapeutic benefits and the mechanism of action on QS and biofilm.