Antibacterial performance of tetracycline-active drugs based on ionic liquids

•Glycolic acid and salicylic acid are selected as anions for the construction of tetracycline ionic liquids.•Tetracycline ionic liquids eliminates the polycrystalline form of tetracycline.•Hydrogen bonding or π-π interaction between tetracycline and anions improves the solubility of tetracycline.•Tetracycline ionic liquids effectively kills tetracycline-resistant Escherichia coli. Active Pharmaceutical Ingredients-Ionic liquids (API-ILs) can overcome the defects of solid drugs without changing the structure of drug molecules and increase drug solubility and bioavailability. In the present work, tetracycline (Tet) was used as the active drug and ethanoic acid (Gly) and salicylic acid (Sa) were selected as the anion to prepare tetracycline ionic liquid ([Tet][Gly] and [Tet][Sa]), respectively. The physical properties of [Tet][Gly] and [Tet][Sa], such as crystallinity, thermal stability and solubility, were investigated. And tetracycline-resistant Escherichia coli was selected as a bacterial model to study the bioavailability changes of tetracycline ionic liquids.