Camphene, C12-C18 fatty acids, and titanium sulfate were used as raw materials to study the synthesis of long-chain fatty acid isobornyl esters. Products were analyzed quantitatively by gas ...chromatography (GC), characterized by nuclear magnetic resonance spectroscopy (hydrogen and carbon), and evaluated using toxicity tests. The optimum reaction conditions were as follows: n(lauric acid):n(camphene) = 2.5:1, m(titanium sulfate):m(camphene) = 0.25:1, reaction temperature of 80 °C, and reaction time of 25 h. Under these conditions, the content of isobornyl laurate in the product was 74.49%, and the content of purified product was 95.02%. The reaction kinetics for isobornyl laurate showed an apparent first-order reaction in the first 9 h with an activation energy of 31.01 kJ/mol. The reaction conditions of myristic acid, palmitic acid, and stearic acid were similar to those of lauric acid, but the reaction time had to be increased as the molecular weight of the fatty acid increased. Toxicity tests for four types of long-chain fatty acid isobornyl esters showed that the samples had low toxicity.
Currently, antibiotic resistance is widespread among bacteria. This problem requires greater awareness because bacterial resistance increases, reducing antibiotic use effectiveness. Consequently, new ...alternative treatments are needed because the treatment options for these bacteria are limited. This work aims to determine the synergistic interaction and mechanism of action of Boesenbergia rotunda essential oil (BREO) against methicillin-resistant Staphylococcus aureus (MRSA). Gas chromatography-mass spectrometry identified 24 BREO chemicals (GC-MS). The main components of BREO were β-ocimene (36.73%), trans-geraniol (25.29%), camphor (14.98%), and eucalyptol (8.99%). BREO and CLX inhibited MRSA DMST 20649, 20651, and 20652 with a minimum inhibitory concentration (MIC) of 4 mg/mL and 512 µg/mL, respectively. The checkerboard method and the time-kill assay revealed synergy between BREO and CLX with fractional inhibitory concentration (FIC) <0.5 and log reduction >2log10 CFU/mL at 24 hours compared to the most effective chemical. BREO inhibited biofilm formation and increased membrane permeability. Exposure alone to BREO or in combination with CLX inhibited biofilm formation and increased cytoplasmic membrane (CM) permeability. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results revealed that alterations in the cell walls, cytoplasmic membrane, and leakage of intracellular components of MRSA DMST 20651 after treatment with BREO alone and in combination with CLX were observed. These results indicate that BREO synergizes and could reverse the antibacterial activity of CLX against MRSA strains. The synergy of BREO may lead to novel drug combinations that increase the effectiveness of antibiotics against MRSA.
