SOLVENT OPTIMIZATION FOR EXTRACTION OF PHENOLIC COMPOUNDS FROM ROSEMARY: A TOOL FOR ALTERING ANTIMICROBIAL ACTIVITY

The antimicrobial activity of phenolic compounds extracted from natural sources has been explored by many industries. In the wound care sector, for example, the application of such extracts may be an alternative to decrease the application of synthetic antibiotics in dressings’ formulations. It is known, however, that the composition and antimicrobial activity of such extracts depend on many factors, including the characteristics of solvents applied. Therefore, this study evaluated the antimicrobial activity of rosemary extracts against microorganisms commonly found in skin wounds, and also investigated the impact of solvent alterations in such activities. For this purpose, ultrasound assisted extractions were carried out using three different solvents: ethanol, acetone and isopropanol, with different water proportions, all selected using computational predictions by conductor-like screening model for real solvents (COSMO-RS), aiming the optimization of rosmarinic acid (RA) extraction. The extracts were characterized by ultra-performance liquid chromatography coupled to a photodiode array and mass spectrometry, had RA quantified, and also had its antimicrobial activity against Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis evaluated through minimal inhibitory concentration (MIC) tests. Extracts produced with ethanol 50%, acetone 50%, isopropanol 50%, ethanol 80%, acetone 90% and isopropanol 80% presented the following RA concentrations, respectively: 7.87, 10.75, 11.23, 21.15, 17.37 and 20.63 mg/g of dry sample. Besides, the different extracts presented distinct antimicrobial activities. For S.epidermidis the best activity was verified in extracts produced with acetone 90% (MIC: 0.0625 mg/mL). For S. aureus, only extracts produced with ethanol 50% presented antimicrobial activity (MIC: 0.5 mg/mL). Regarding P. aeruginosa, all extracts presented similar activities (MIC 2.0 mg/mL), except for ethanol 50% extracts, which did not present antimicrobial activity. The obtained results evidenced the efficiency of COSMO-RS for solvent optimization, and also revealed that the resulting composition alterations affected the antimicrobial activities of the extracts.