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Thiazolium salts are structurally analogous to the most common imidazolium-based ionic liquids (ILs), and are supposed to be a new class of ILs. However, there are up to now only a few reports and absence of systematic study on thiazolium ILs. In this work, several thiazolium-based ILs were prepared, characterized and comparatively studied. Most of the thiazolium ILs are liquid at room temperature, with melting points below 43.0 °C. Good thermal stability was observed for thiazolium ILs, resulting in thermal decomposition temperatures up to 264 ∼ 358 °C. In comparison with the conventional imidazolium ILs, thiazolium ILs exhibit moderate density, refractive index and surface tension, which all generally decrease with temperature. According to the temperature-dependent viscosity and conductivity, thiazolium ILs follow fractional Walden’s rule, indicating strong ion-ion coupling. Besides, thiazolium ILs display relatively narrow electrochemical window (3.1 ∼ 4.0 V).

Green extraction of natural products from plants is of high importance to the pharmaceuticals and fine chemicals industry. Novel bio-renewable ionic liquids, a class of safe and powerful medium, has aroused broad attention from the field of extraction and separation. In the present study, the 1-amino-2-propanol-based ionic liquids (PA-ILs) were used to selectively extract the antioxidants from Mugwort (Artemisia argyi Levl. et Vant.). As revealed from the results, among ten PA-ILs carrying different counter anions, the PA/mandelic acid, PA/EDTA and PA/lactic acid exhibited the best extraction efficiency to polyphenols (120.34 mg/g), flavones (128.87 mg/g) and polysaccharides (43.62 mg/g), respectively. Furthermore, the time-dependent DPPH radical scavenging shown that flavones are the major antioxidants and PA-ILs extractants were higher than those of conventional solvents. According to the reversed-phase HPLC profiles, more polar substances (e.g. glycosides) existed in ILs extract compared with alcohols solvent. The Fermi resonance in the FT-IR spectrum indicated the complex H-bonding framework in ILs, which may act as a crucial factor to assess extraction performance. Moreover, the in vitro studies reported that the cytotoxicity of PA-ILs for HaCaT and Caco-2 cell lines was less than that of pure PA. It was, therefore, demonstrated that PA-ILs are a secure medium that can help alternate organic solutions.