Screening of Hydrophilic Deep Eutectic Solvents for Ultrasound Probe-assisted Extraction of Rosmarinic Acid from Salvia officinalis with High Performance Liquid Chromatography Analysis

Abstract

This study investigates the potential of hydrophilic deep eutectic solvents (DESs) for the extraction of rosmarinic acid (RA) and antioxidant compounds from Salvia officinalis (sage) using ultrasound probe-assisted extraction. Six DESs were formulated using choline chloride (ChCl) as the hydrogen bond acceptor and either ethylene glycol or glycerol as the hydrogen bond donor, in molar ratios of 1:1, 1:2, and 2:1. All DESs were prepared without added water. Under fixed extraction conditions (10 min, 30% amplitude, 1:10 solid–liquid ratio), the RA content was quantified by high-performance liquid chromatography (HPLC). Among the DESs, ChCl:glycerol, 1:2 (DES-5) showed the highest extraction potential exhibited by the highest peak intensity in the chromatogram and was selected for further investigation. Antioxidant activity of DES-5 was assessed via the ORAC assay. Methanol was used as a reference solvent for comparison. The ORAC value of methanol extract was 9,270 ± 2.82 µmol TE/ 100 ml, while that of DES-5 was 33,690 ± 4.98 µmol TE/100 ml, indicating a stronger radical scavenging capacity in DES-5 extract. Based on the promising ORAC value observed, DES-5 extract was further explored by modifying its composition through the addition of water; 10%, 20% and 30%, to evaluate it effect on RA yield. Results revealed that moderate water addition of 10% enhanced RA recovery, resulting in the highest yield of 73.38 mg/g DW RA compared to 66.59 mg/g DW at 20% water and 72.39 mg/g DW at 30% water. The study demonstrates the viability of DESs, particularly DES-5, as sustainable alternatives to conventional solvents for the recovery of bioactives from medicinal plants.