Microwave‐Assisted Preparation of an Acidic Deep Eutectic Solvent: Green Analysis, Characterization and Application

• Published in: ChemistrySelect (Weinheim) 2024-05, Vol.9 (18), p.n/a
• Main Authors: Yap, Pei Gee, Wang, Yong, Gan, Chee Yuen
• Format: Article
• Language: English
• Subjects: and polysaccharide; antioxidants; deep eutectic solvent; green chemistry; microwave approach
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.202400836

Microwave irradiation was postulated to reduce time and energy for deep eutectic solvent (DES) production which is in line with the principle of green chemistry. In this study, the choline chloride (ChCl)‐malic acid (MA) DES was prepared using microwave‐assisted (DES‐Mic) and conventional (DES‐Con) approaches. Microwave was a relatively greener approach as it was rapid (5 min) and consumed 92.8 % energy less than DES‐Con. Moreover, DES‐Mic and DES‐Con exhibited similar physicochemical profiles (pH, solubility, density) and rheological properties. Structural profiling through FTIR analysis suggested hydrogen bond formation between the functional groups of ChCl and MA. The FTIR spectra also did not show structural differences in the DES synthesized using different methods. DES‐Mic and DES‐Con exhibited superior 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) (80.8±0.1 and 83.2±0.3 %, respectively) free radical scavenging activities than ChCl (15.6±0.8 %), MA (20.0±1.4 %) and ChCl:MA aqueous mixture without subjected to DES synthesis conditions (ChCl:MAaq; 23.3±0.8 %). Both DES were also proven as more efficient solvents for the extraction of polysaccharides from ramie leaf, as they recorded higher yields (21.4±1.9 and 22.2±1.0 %, respectively) than equimolar of MA (17.7±2.6 %) and ChCl (6.4±0.2 %). Overall, microwave was proven as a more sustainable approach for DES preparation compared to conventional method, which could be further improvised for industrial applications. Microwave irradiation as a greener approach for deep eutectic solvent (DES) preparation. This approach consumes less time (5 min) and energy (92.8 %) than conventional heating and stirring method. The DES exhibits similar physicochemical and rheological properties with conventionally prepared DES. It also shows antioxidant and polysaccharide extraction properties with potential application in the food processing industry.