Abstract

This was the first study to use local Southern Thai ingredients, namely, nipa palm syrup (NS) and nipa palm vinegar (NV), in the formulation of natural deep eutectic solvent (NADES) for the recovery of bioactive curcumin from turmeric. Five NADES formulations (A to E) were obtained by varying concentration of liquid media (NS, NV, and water) and characterized using FTIR. When compared to other formulations and 80% methanol, the NADES D with a NS to NV to water ratio of 1:5:5 (w/w/w) recovered the most curcumin content (p < 0.05). The extraction conditions of microwave-assisted extraction (MAE) with selected NADES were optimized using response surface methodology (RSM) to maximize curcumin recovery. NADES D achieved the highest curcumin content (43.04 mg/g) from turmeric at a solvent ratio of 1:10, microwave power of 1000 W, and extraction time of 51 s. The NADES D-based curcumin extract outperformed all antioxidant activities (DPPH^∙ scavenging activity and FRAP). The NADES D–based extract is non-toxic to RAW264.7 cells at up to 62.50 µg/mL. As a result, NADES-based NS and NV are a viable green solvent for obtaining bioactive compounds, particularly curcumin from turmeric.