Surfactant assisted extraction for the recovery of bioactive compounds from solid wastes of lavender (Lavandula angustifolia Mill): Optimization by Box-Behnken Design

This study explored the potential of solid waste from the essential oils industry as a source of valuable phenolic compounds. The extraction of bioactive compounds as well the assessment of antioxidant activity and antimicrobial properties from the solid residues of Lavandula angustifolia Mill. was investigated using surfactant assisted extraction. Nonionic surfactant: Genapol X-080 was chosen as the additive for the extraction process. Response Surface Methodology (RSM) utilizing the Box-Behnken Design (BBD) was selected to optimize the effects of solvent-to-solid ratio (10-30 mL/g), ethanol concentration (40-80 %), time of extraction (120-360 min), and Genapol X-080 concentration (0-3 %). The optimal conditions for extraction were: 10 mL/g a ratio of solvent-tosolid, 80 % an ethanol concentration, 248.64 min an extraction time and 2.13 % a surfactant concentration. Using these conditions, the total polyphenol content was 52.21 +/- 0.61 mg GAE/g, the flavonoid content was 11.28 +/- 0.14 mg QE/g, and the IC50 value for DPPH inhibition was 0.447 +/- 0.013 mg/mL. Additionally, HPLC analysis revealed the presence of seven phenolic acids and four flavonoids compounds. Antimicrobial testing revealed that the extract was effective against Staphylococcus aureus, Listeria monocytogenes, and Bacillus subtilis, but not against Escherichia coli and the fungus Umbelopsis ramanniana. Listeria monocytogenes showed the greatest sensitivity to the tested extract.