Deep eutectic solvent-based extraction of rosemary leaves: optimization using central composite design and evaluation of antioxidant and antimicrobial activities

Abstract

Rosemary (Rosmarinus officinalis) is a member of the Lamiaceae family with antioxidant and antimicrobial properties. Traditional extraction methods often require large amounts of organic solvents, decreasing extract quality. This study used deep eutectic solvents (DESs) as an alternative for extracting bioactive compounds from rosemary leaves. The effects of ultrasonic time, temperature, and plant amount on extraction were optimized. Under optimized conditions, the yield of total polyphenols was 18.50 ± 1.65 mg GAE g⁻¹. The DES extract showed superior antioxidant activity (88–92% inhibition) and potent antimicrobial activity against various microbial strains, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. The DES extract exhibited larger inhibition zones compared to the methanolic extract. Cytotoxicity assessments revealed no adverse effects. These findings highlight the potential of DESs as green and efficient extraction solvents for bioactive compounds from rosemary, with implications for natural products with antioxidant, antimicrobial, and therapeutic applications.