Direct Terpene extraction from aromatic herbs: Comparative evaluation of ultrasound-assisted stir bar sorptive extraction and ultrasound-assisted extraction by HPLC-PDA with AGREE/AGREEprep greenness assessment

This study presents the development and comparison of two extraction methods: ultrasound- assisted stir bar sorptive extraction with liquid desorption (UA-SBSE-LD) and ultrasound-assisted extraction (UAE) for the isolation and quantification of six major terpenes and terpenoids (thymol, carvacrol, eugenol, p-cymene, γ-terpinene, and α-pinene) from culinary aromatic herbs. The analytes were analyzed by high-performance liquid chromatography with photodiode array detection (HPLC-PDA). For UA-SBSE-LD, the effects of key extraction parameters, including adsorption time, ionic strength, pH, desorption solvent composition, desorption time, and solid:liquid ratio, were investigated, while UAE was evaluated using a water–ethanol system without pH adjustment. Both techniques demonstrated excellent linearity (R² ≥ 0.9805), acceptable detection limits (0.21–17 µg/mL), and satisfactory recoveries (82–120%), meeting validation requirements. Applied to thyme, oregano, rosemary, and basil, UA-SBSE-LD outperformed UAE for volatile hydrophobic compounds like γ-terpinene and α-pinene, yielding higher extraction efficiencies without organic solvent pretreatment. UA-SBSE-LD achieved up to 6.89 mg/g of α-pinene from rosemary and 4.04 mg/g of eugenol from basil. The sustainability of the methods was evaluated using AGREE and AGREEprep tools, indicating a greener profile for UAE. The direct application of UA-SBSE-LD to solid plant matrices, coupled with HPLC-PDA, represents a sensitive alternative to gas chromatography-based methods for determining terpenes in food matrices.