Optimization of phenolic acid extraction from Origanum species via novel deep eutectic solvents using response surface methodology

Abstract

In this study, novel deep eutectic solvents (DES) were synthesized and evaluated for their potential in extracting phenolic acids from Origanum micranthum and Origanum minutiflorum. The characterization of DES was carried out using FTIR and DSC techniques. Extraction parameters, including DES volume, extraction temperature, and vortex time, were optimized using the Box-Behnken design under the Response Surface Methodology (RSM) framework. The optimal conditions led to a high extraction efficiency, with a determination coefficient (R²) of 0.9727, a coefficient of variation (CV) of 5.08%, and a signal-to-noise ratio of 14.47. Seven phenolic compounds were identified, with benzoic acid being the most abundant. Antioxidant activities were assessed via CUPRAC, FRAP, and DPPH assays, revealing that 1-hexadecanol-thymol and 1-octadecanol-thymol DES mixtures provided significant activity enhancements. Antimicrobial tests demonstrated inhibitory effects against Candida albicans, Staphylococcus aureus, Bacillus cereus, and Staphylococcus epidermidis, while Escherichia coli remained unaffected. The results indicate that natural DESs are promising, sustainable solvents for phenolic extraction with notable biological activities. This study contributes to green chemistry by introducing environmentally friendly solvent systems for efficient bioactive compound recovery.