Designing Natural Deep Eutectic Solvents for Extraction of Phenolic Compounds and Antioxidant Application: A Case Study with Diverse Thai Rice Bran Varieties

Green solvents, like natural deep eutectic solvents (NaDES) derived from biobased molecules, are gaining prominence over conventional solvents due to their eco-friendly, less toxic, biodegradable, and cost-effective attributes. This study focuses on NaDES derived from food-grade compounds for extracting phenolic compounds and anthocyanins from different rice bran types, comparing them with ethanol and 10% acidic water. NaDES formulations displayed superior extraction efficiency for both phenolic compounds and anthocyanins in bound and free forms. Notably, the betaine/sucrose/water NaDES extracted the highest antioxidant compounds from the Niaw Dum Mor variety, showing 7 times higher antioxidant activity than ethanol in (2,2)-diphenyl-1-picrylhydrazyl assays and 2.5 times higher in oil-in-water emulsion systems. This study highlights the effectiveness of betaine-based NaDES with sucrose in extracting phenolic compounds, offering a sustainable approach for future antioxidant extract formulations.