Natural deep eutectic solvent extraction of xanthorrhizol and curcuminoids from Curcuma xanthorrhiza Roxb and simultaneous determination by high-performance liquid chromatography

Context: Curcuma xanthorrhiza, a native to Indonesia, has been recognized as a potential medicinal plant. Xanthorrhizol (XTZ), curcumin (Cur), bisdemethoxycurcumin (BDMC), and demethoxycurcumin (DMC) are the main major metabolites with different bioactivities. Thus, the selective extraction of these markers is required. Aims: To characterize and use natural deep eutectic solvents (NADES) for the extraction of XTZ and curcuminoids (CURS) from C. xanthorrhiza. Methods: Four NADES, comprising of glucose:lactic acid (Glu:LA, 1:3), choline chloride: malic acid (ChCl:MA, 1:1), choline chloride: glycerol (ChCl:Gly, 1:1), and choline chloride: sucrose (ChCl:Suc, 3:1) were synthesized and subjected to FTIR. The physicochemical properties of NADES were characterized, including polarity, viscosity, and density. Their antioxidant profiles were evaluated. The toxicity of NADES was assessed towards Escherichia coli by real-time growth monitoring. Tested NADES were employed to extract marker compounds from the rhizome of C. xanthorrhiza. A validated high-performance liquid chromatography (HPLC) method was applied to simultaneously quantify XTZ and CURS in NADES extracts. Results: FTIR spectra confirmed the formation of hydrogen bonds between components. Using the DPPH and FRAP methods, all NADES and NADES extracts displayed antioxidative activity, suggesting the contribution of NADES to the activity. Of the tested NADES, Glu:LA (1:3) obtained the highest content of XTZ over Cur, BDMC, and DMC, comparable to that of ethanol maceration. All tested NADES were harmless to E. coli, except for ChCl:MA (1:1). However, NADES extracts of Glu:LA (1:3) and ChCl:MA (1:1) suppressed the growth of the bacterium. Scanning electron micrographs demonstrated the destruction of the surface structure of the rhizome powder by NADES-ultrasonication. Conclusions: The study recommended the use of Glu:LA (1:3) to selectively extract XTZ to promote environmentally friendly and sustainable extraction.