Characteristics of Xanthorrhizol Rich Extract from Curcuma xanthorrhiza in the Choline Chloride-Based Natural Deep Eutectic Solvents: DNA Protective Activity and Toxicity Profiles

Xanthorrhizol, a bioactive compound with different health benefits, is present in the rhizomes of Curcuma xanthorrhiza in abundance. In this work, natural deep eutectic solvent (NADES) based on choline chloride (CC) and organic acids (lactic acid, malic acid, and citric acid) were used as green solvent alternatives to organic solvents to extract xanthorrhizol from C. xanthorrhiza. CC-based NADESs and xanthorrhizol extracts were characterized. Three different native NADES were applied in this study, namely choline chloride-citric acid (CC-CA), choline chloride-malic acid (CC-MA), and choline chloride-lactic acid (CC-LA). The antioxidant, DNA damage protective, and toxicity activities were investigated. The results showed that all NADES were more polar than ethanol. All NADES were viscous and had density more than water and ethanol. The FTIR studies confirmed the formation of hydrogen bonds between the two components (choline chloride and organic acids). Due to its lowest viscosity, CC-MA was selected for xanthorrhizol extraction. HPLC analysis showed that extraction using CC-MA obtained similar amounts of xanthorrhizol and curcuminoids. NADES and their extracts showed DPPH radical scavenging and Fe³⁺ reducing activities. Although weaker than ethanol extract, all solvents and their extracts mitigated H2O2-induced oxidative damage to pBR322 plasmid DNA. Based on a real-time bacterial assay, all NADES and their extracts were benign to Staphylococcus aureus. However, NADES were more active against Escherichia coli, although their respective extracts are less toxic to E. coli. In conclusion, CC-MA NADES is the novel green extraction solvent for xanthorrhizol. Its low toxicity allows for potential application as a protective DNA damage agent.