Interaction of indomethacin–cyclodextrins in water by UV–Vis and ITC

Small molecules interfacial assembly regulate the crystallization transition process for nobiletin stabilization

Many bioactive nutraceuticals naturally occurring in food materials possess beneficial biological activities, while their use as functional supplements is subjected to hydrophobicity and crystallinity. Currently, inhibiting crystallization for such nutrients is of immense scientific interest. Here, we exploited diverse structural polyphenols as potential inhibitors for restraining Nobiletin crystallization. Specifically, the crystallization transition process could be influenced by the polyphenol gallol density, Nobiletin supersaturation (1, 1.5, 2, 2.5 mM), temperature (4, 10, 15, 25 and 37 ℃), and pH (3.5, 4, 4.5, 5), important factors for regulating the binding attachment and interactions. The optimized samples could be guided by NT100 lied in 4 ℃ at pH 4. Besides, the main assembly driving force was hydrogen-bonding cooperated with π-π stacking and electrostatic interaction, leading to a Nobiletin/TA combination ratio of ∼ 3:1. Our findings proposed an innovative synergistic strategy for inhibiting crystallization and broaden potential applications of polyphenol-based materials in advanced biological fields.

Complexation of caffeine and theophylline with epigallocatechin gallate in aqueous solution: Nuclear magnetic resonance, molecular docking and thermodynamics studies

Epigallocatechin gallate (EGCg) and methylxanthines are representative bioactive compounds in tea leaves, the strong affinity between them will elicit destruction of tea quality. In order to elucidate the mechanism of complexation between EGCg and methylxanthines, we compared the bindings of theophylline and caffeine to EGCg by nuclear magnetic resonance (NMR), molecular docking and isothermal titration calorimetry (ITC). The results revealed that the stoichiometries of caffeine to EGCg and theophylline to EGCg were both 1:1. Caffeine and theophylline were captured in the hydrophobic space formed by aromatic rings of EGCg. The affinity between EGCg and caffeine was stronger than that between EGCg and theophylline, which could be partially attributed to the two extra CH-π interactions between N₇-Me of caffeine and aromatic rings of EGCg. Furthermore, the results of ITC were agreed well with NMR and molecular docking, indicating that ITC was possible to accurately evaluate the complexation.

Role of green tea nanoparticles in process of tea cream formation - A new perspective

Green tea nanoparticles (gTNPs) are considered as the precursors of tea cream, while the role of gTNPs in the process of tea cream formation remains obscure. This study indicated that gTNPs could be coated with epigallocatechin gallate (EGCG)-caffeine (CAF) complexes to form a ternary aggregate participating in tea cream formation. First, the ζ-potentials of gTNPs and EGCG-CAF complexes were adjusted by charge screening. Then, gTNPs were introduced into EGCG + CAF mixture solutions under different ζ-potential conditions to examine their effect on turbidity, particle size and components of mixture solutions. Finally, isothermal titration calorimetry (ITC) was applied to investigate the influence of gTNPs on the thermal effects of the interaction between EGCG and CAF. Our results reveal that hydrophobic interaction exceeded electrostatic repulsion to dominate the interaction between gTNPs and EGCG-CAF complexes at the low ζ-potential condition, thus forming the gTNPs/EGCG/CAF ternary aggregate.

Thermodynamics of inclusion within cyclodextrins and structural evidence of Cu(indomethacin)2 and Zn(indomethacin)2 complexes in aqueous solutions

Cu(IMC)₂ and Zn(IMC)₂ inclusion within cyclodextrins is spontaneous, the former driven by entropic and the last by enthalpic contributions.