Preparation, characterization, and evaluation of HP-ß-CD inclusion complex with alcohol extractives from star anise.

The active compounds in star anise alcohol extractives (SAAE) have potent bioactivity. However, their poor solubility and stability limit their applications. In this study, SAAE/hydroxypropyl-ß-cyclodextrin (HP-ß-CD) inclusion complexes were prepared as a strategy to overcome the abovementioned disadvantages. The phase solubility results indicated that the solubility of the inclusion complex was enhanced. Complexation was confirmed by complementary methods, including Fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, and transmission electron microscopy, which proved to be extremely insightful for studying the inclusion formation phenomenon between SAAE and HP-ß-CD. Despite there being no apparent improvements in the antioxidant capacity and antimicrobial activity, the results of the stability studies presented higher thermal, volatile, and photostability after encapsulation. Further, molecular modeling was used to investigate the factors influencing complex formation and provide the most stable molecular conformation. Thus, based on the obtained results, this study strongly demonstrates the potential of the SAAE/HP-ß-CD inclusion complex in the food industry.

Enantioseparation of three isomeric α-(chlorophenyl)propanoic acid by countercurrent chromatography and investigation of chlorine substituent through characterization of inclusion interaction.

The influence of chlorine substituents in chiral separation of three racemic 2-(chlorophenyl)propanoic acids by countercurrent chromatography using hydroxypropyl-ß-cyclodextrin as a chiral additive were mainly investigated in the present paper, including 2-(2-chlorophenyl)propanoic acids, 2-(3-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids. The influences of chromatographic conditions on the retention behavior were studied by enantioselective liquid-liquid extraction experiments using the methodology of response surface It was found that 2-(3-chlorophenyl)propanoic acids could be successfully chiral separated by countercurrent chromatography, while no resolution was achieved for racemic 2-(2-chlorophenyl)propanoic acids and 2-(4-chlorophenyl)propanoic acids under optimized separation conditions. The formation of 1:1 stoichiometric inclusion compounds between 2-(3-chlorophenyl)propanoic acids and HP-ß-CD was determined by UV spectra measurements. The inclusion constants for 2-(3-chlorophenyl)propanoic acids and HP-ß-CD were determined by the Benesi-Hildebrand equation. Meanwhile, the inclusion constants of 2-(3-chlorophenyl)-propanoic acid enantiomer and HP-ß-CD were obtained by the pesudophase retention equation in countercurrent chromatography. Furthermore, the inclusion interactions of the three racemates with HP-ß-CD were also investigated by the molecular docking. The results obtained from UV spectra measurements and molecular docking showed that the racemate with chlorine substituents in meta-position presented the highest enantiorecognition while the racemates with chlorine substituents in ortho-position had the lowest enantiorecognition. The above results further indicated that forming a stable inclusion complex between racemate and chiral selector is a prerequisite for a successful enantioseparation and at the same time, the difference in inclusion capacity between the two enantiomers is also essential for the enantioseparation.

Spectroscopic methods for aqueous cyclodextrin inclusion complex binding measurement for 1,4-dioxane, chlorinated co-contaminants, and ozone.

Recalcitrant organic contaminants, such as 1,4-dioxane, typically require advanced oxidation process (AOP) oxidants, such as ozone (O3), for their complete mineralization during water treatment. Unfortunately, the use of AOPs can be limited by these oxidants' relatively high reactivities and short half-lives. These drawbacks can be minimized by partial encapsulation of the oxidants within a cyclodextrin cavity to form inclusion complexes. We determined the inclusion complexes of O3 and three common co-contaminants (trichloroethene, 1,1,1-trichloroethane, and 1,4-dioxane) as guest compounds within hydroxypropyl-ß-cyclodextrin. Both direct (ultraviolet or UV) and competitive (fluorescence changes with 6-p-toluidine-2-naphthalenesulfonic acid as the probe) methods were used, which gave comparable results for the inclusion constants of these species. Impacts of changing pH and NaCl concentrations were also assessed. Binding constants increased with pH and with ionic strength, which was attributed to variations in guest compound solubility. The results illustrate the versatility of cyclodextrins for inclusion complexation with various types of compounds, binding measurement methods are applicable to a wide range of applications, and have implications for both extraction of contaminants and delivery of reagents for treatment of contaminants in wastewater or contaminated groundwater.