Synthesis of a New Imidazole Amino Acid Ionic Liquid Polymer and Selective Adsorption Performance for Tea Polyphenols

Preparation of imidazolium ionic liquid functionalized paper membrane for selective extraction of caffeic acid and its structural and functional analogues from Taraxaci Herba

In the search for pharmaceutically active compounds from natural products, it is crucial and challenging to develop separation or purification methods that target not only structurally similar compounds but also those with specific pharmaceutical functions. The adsorption-based method is widely employed in this field and holds potential for this application, given the diverse range of functional monomers that can be chosen based on structural or functional selectivity. In this work, an imidazolium ionic liquid (IL) modified paper membrane was synthesized via microwave reaction. Caffeic acid (CA), with potential interactions with imidazolium IL and a representative component of phenolic acids in Taraxaci Herba, was chosen as a target compound. After optimization of synthesis and extraction parameters, the resulting extraction membrane could be used to quantitatively analyze CA at ng/ml level, and to extract CA's analogues from the sample matrix. Cheminformatics confirmed the presence of structural and functional similarity among these extracted compounds. This study offers a novel approach to preparing a readily synthesized extraction membrane capable of isolating compounds with structural and functional analogies, as well as developing a membrane solid-phase extraction-based analytical method for natural products.

Advances of Imidazolium Ionic Liquids for the Extraction of Phytochemicals from Plants

In this review, we present the research from 2013 to 2022 about the character of ionic liquids, the categories of phytochemicals, and the reasons for selecting imidazolium ionic liquids for phytochemical extraction. Then we introduce the structural formulae of the imidazolium ionic liquids commonly used in the extraction of phytochemicals, the methods used to prepare imidazolium ionic liquids, and a comprehensive introduction of how imidazolium ionic liquids are applied to extract phytochemicals from plants. Importantly, we discuss the strategies for studying the extraction mechanisms of imidazolium ionic liquids to extract phytochemicals, and the recovery methods regarding imidazolium ionic liquids and their recyclability are analyzed. Then the toxicity in imidazolium ionic liquids is pointed out. Finally, the challenges and prospects of extracting phytochemicals by imidazolium ionic liquids are summarized, and they are expected to provide some references for researchers.

Exploring the Absorption Mechanisms of Imidazolium-Based Ionic Liquids to Epigallocatechin Gallate

Imidazolium-based ionic liquids are wildly used in natural product adsorption and purification. In this work, one typical polymeric ionic liquid (PIL) was synthesized by using L-proline as the anion, which exhibited excellent adsorption capacity toward tea polyphenol epigallocatechin gallate (EGCG). The adsorption conditions were optimized with the response surface method (RSM). Under the optimum conditions, the adsorption capacity of the PIL for EGCG can reach as high as 552 mg/g. Dynamics and isothermal research shows that the adsorption process of EGCG by the PIL particularly meets the quasi-second-order kinetic equation and monolayer adsorption mechanism. According to thermodynamic parameter analysis, the adsorption process is endothermic and spontaneous. The results of theoretical calculation by molecular docking also demonstrated the interaction mechanisms between EGCG and the ionic liquid. Considering the wide application of imidazolium-based ionic liquids in component adsorption and purification, the present study can not only be extended to other similar experimental mechanism validation, but also be representative for guiding the synthesis of PIL and optimization of adsorption conditions.

Synthesis and photophysical properties of benzoxazolyl-imidazole and benzothiazolyl-imidazole conjugates

Materials that have higher fluorescence emission in the solid state than molecules in solution have recently been paid more attention by the scientific community due to their potential applications in various fields. In this work, we newly synthesized benzoxazolyl-imidazole and benzothiazolyl-imidazole conjugates, which show aggregation-induced emission (AIE) features in their solid and aggregate states. It was found that oxygen and sulfur substitutions can dramatically influence the molecular structures and polarities of the dyes, leading to different degrees of the AIE phenomenon. The benzothiazolyl-imidazole molecule has lower polarity compared to that of benzoxazolyl-imidazole; therefore, the dye bearing a benzothiazolyl group shows higher emission intensity and dual emission in aqueous solution. Theoretical calculation results suggest that the benzothiazolyl-imidazole molecules might have electrostatic interactions between sulfur and nitrogen atoms, explaining the experimental observations of lower critical aggregation concentration and photophysical properties both in solution and in the solid state. The theoretical calculations agree with the experimental data, thus demonstrating a potent strategy to gain a deep understanding of the structure–property relationships to design solid-state fluorescent materials.

The effect of heteroatoms on the structural and photophysical properties of donor-π-acceptor molecules, comprising imidazole and benzoxazolyl as well as imidazole and benzothiazolyl units, was investigated.