Study on Efficient Extraction of Curcuma longa Essential Oil Using Natural Deep Eutectic Solvents Screened by COSMO-RS Combined with Ultrasonic Assistance and Its Mechanism

This study developed an eco-friendly and efficient natural deep eutectic solvent-based ultrasound-assisted hydrodistillation (NADES-U-HD) method for Curcuma longa essential oil (CEO) extraction. First, 4 ideal NADESs were screened from 1225 combinations via the Conductor-like Screening Model for Real Solvents (COSMO-RS). Then, structural and physical property characterizations were carried out. Combined with extraction experiments, [Lauric acid] [Oleic acid] ([LA][OA]) was identified as the best-performing NADES, consistent with COSMO-RS predictions. The best extraction parameters were determined: ultrasonic temperature = 40 °C, time = 28 min, power = 320 W, and ratio of NADES to turmeric powder = 1.71:1 mL/g, achieving an average CEO yield of 12.049%. The NADES-U-HD method delivered the highest yield (74.70% higher than HD), elevated relative contents of key active components (Ar-turmerone, turmerone, curlone), and enhanced cell viability and antioxidant activity. Mechanistic investigations by powder characterizations, quantum chemical (QC) calculations, and molecular dynamics (MD) simulations revealed that LA and OA form hydrogen bonds (HBs) with cellulose, disrupting the cell wall HB network to facilitate CEO release. The main CEO components interact with LA/OA hydroxyl groups via O–H···O HBs (through their carbonyl O) and van der Waals (vdW) forces, promoting dissolution in NADES and boosting extraction efficiency. This work provides a green and efficient method for CEO extraction, deepens insight into the NADES-U-HD process and its extraction mechanism, and offers a theoretical basis for industrial applications.