Evaluation of the volatiles’ chemical profile and antibacterial activity of Lavandula stoechas L. extracts obtained by supercritical carbon dioxide

The goal of this study was to establish a green methodology for obtaining safe, high-quality, and potent antibacterial extracts of Lavandula stoechas flowers. Supercritical carbon dioxide (scCO2) at different conditions (pressure 100–300 bar, temperature 40 and 60 °C, and CO2 flow 10–30) was applied. Moreover, the impact of the parameters on the extraction yield, chemical profile of the extracts, and the activity against Gram-positive and Gram-negative bacteria was investigated. ScCO2 extraction kinetics was investigated by modelling the extraction curves using the models described by Brunner, Martinez, and their modifications. In vitro assays were applied to estimate the susceptibility of Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus to extracts. A pattern recognition approach was applied to explore the correlations between the employed scCO2 parameters, detected volatile compounds, and extracts’ antibacterial properties. The achieved yield ranged from 1.17 to 2.4% (w/w), with oxygenated monoterpenes fenchone (5.76–22.72%) and verbenone (8.04.-18.65%) as the most abundant ones. The most significant susceptibility of Gram-positive and Gram-negative bacteria was attributed to extracts obtained at 200 bar, with minimal inhibitory concentration in the range 2.71 ± 1.31–20.69 ± 0.91 mgmL−1 and 3.39 ± 0.48–34.28 ± 5.94 mgmL−1, respectively. The obtained extracts represent safe, viable, and promising alternatives for tackling antimicrobial resistance. Moreover, by varying process conditions, it is possible to adjust the chemical profile and the activity of the extracts according to the target purpose. Furthermore, the requirements of clean and sustainable technologies, such as environmental preservation, rational use of renewable resources, and provision of natural, safe, and high-quality extracts can be met.