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In this study the physicochemical characterization of the pulp and almond fixed oil was carried out; their antibacterial activity and aminoglycoside antibiotic modifying action against standard and multiresistant Gram-positive and -negative bacteria were investigated using the broth microdilution assay. Physical properties such as moisture, pH, acidity, peroxide index, relative density and refractive index indicate stability and chemical quality of the oils. In the GC/MS chemical composition analysis, a high unsaturated fatty acid content and the presence of oleic and palmitic acids were observed in the oils. In the antibacterial assay, more significant results were obtained for Escherichia coli, while other standard and multi-resistant strains presented MIC values ≥ 1024 μg/mL. Furthermore, the fixed oils in association with antibiotics were able to significantly improve antibacterial activity against S. aureus with a reduction in MICs. [ABSTRACT FROM AUTHOR]

Essential oils are new natural medicines, which have been studied extensively in recent years. In this paper, the chemical composition of the essential oil from Alpinia zerumbet leaves and its ability to modulate the activity of aminoglycoside antibiotics is reported. The essential oil was extracted by hydrodistillation and analyzed by gas chromatography (GC) and GC–mass spectrometry (GC/MS). The antibacterial activity of the essential oil alone or in association with aminoglycosides was determined by a microdilution test against twelve strains (standards and multi-resistant clinical isolates obtained from sputum and wounds), seven Gram negative and five Gram positive. The major components identified by GC/MS were 4-terpineol (32.9 ± 4.0%), 1,8-cineole (21.4 ± 1.2%), γ-terpinolene (10.0 ± 1.8%) and sabinene (7.1 ± 4.6%), with a strong predominance of monoterpenes. The results indicated that the multi-resistant clinical isolates Staphylococcus aureus 358 and Escherichia coli 27 were more sensitive to the essential oil, exhibiting minimum inhibitory concentrations (MICs) of 32 and 128 μg/mL, respectively. The essential oil was capable of enhancing the antimicrobial activity of aminoglycosides against all strains tested, except for S. aureus 358. Very significant reductions in the MICs of the antibiotics were found, with a 94% decrease in MIC of neomycin against Klebsiella pneumoniae ATCC 10031. The results obtained indicate that the A. zerumbet essential oil has a significant synergistic antibiotic effect when combined with aminoglycosides, demonstrating that its constituents may act as potentiators of the antibiotic activity of aminoglycosides. [ABSTRACT FROM AUTHOR]