Antioxidant Properties of Curcuma caesia Extracted Using Natural Deep Eutectic Solvent

Plants serve as viable sources for obtaining natural antioxidants. Among the potentially rich sources of antioxidants, black turmeric rhizome (Curcuma caesia) stands out. Traditionally, the conventional method for extracting bioactive chemicals from plants has relied on the utilisation of organic solvents, despite its recognised environmental drawbacks. However, an alternate technique that aligns with environmental consciousness involves the application of natural deep eutectic solvents (NADES). This study targeted to create and characterize four types of NADES designated as follows: NADES 1-citric acid:sucrose (1:1); NADES 2-sucrose:glucose:fructose (1:1:1); NADES 3-choline chloride:glycerol (1:1:2); and NADES 4- glycerol:urea (1:1) at 70°C. The investigation involved the determination of the physical properties of these NADES, including pH, temperature, and density. All formulated NADES were used to ascertain the entire phenolic and flavonoid content of C. caesia rhizomes, and their antioxidant potential was determine using 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging and ferric reducing antioxidant power (FRAP) methods. The results revealed a pH sequence of NADES 1<NADES 2