Characterization of bergamot essential oil: chemical, microbiological and colloidal aspects

Abstract

Citrus bergamia is a citric species known as bergamot. The species is widely used due to its derivatives, such as juices, extracts, and essential oil. Specifically, the bergamot essential oil (BEO) is of great interest, with a chemical composition rich in terpenes and esters. Considering its chemical composition, bioactivity, and great economic potential, the characterization of BEO should be studied. However, this essential oil is almost unexplored in terms of a characterization associated with colloids. Chemical characterization was carried out by gas-chromatography coupled to a mass spectrometer and by gas-chromatography coupled to a flame ionization detector. Antibacterial activity against Staphylococcus aureus and Escherichia coli was carried out to confirm the bioactivity of this important essential oil. Dynamic light scattering analysis was performed to create a pattern of droplet size distribution of BEO. Major compounds of BEO were linalyl acetate, limonene, and linalool. The BEO was active against E. coli and presented a MIC value of 2.000 µg/mL, while values of MIC and MBC higher than 2.000 µg/mL were observed for S. aureus. The dynamic light scattering analysis revealed a mean hydrodynamic diameter of 65.7 ± 2.2 nm. After a 1:10 dilution it was observed reduction of mean diameter and enhancement of the percentagem of low size droplets, resepctively 44.1 ± 1.2 nm and 14.5 ± 0.5 nm (28.8 ± 1.2%). Higher droplets and reduced polydispersity index were observed after 1:100 dilution. In the present study, the chemical characterization was in accordance with the species, as the characteristic chemical markers of the species were found. Moreover, it has presented antibacterial activity as expected for the BEO. The analysis of the colloid showed a pattern of droplet size distribution following the Ostwald ripening mechanism after dilution.