Niosomes Consisting of Tween-60 and Cholesterol Improve the Chemical Stability and Antioxidant Activity of (−)-Epigallocatechin Gallate under Intestinal Tract Conditions

In order to improve the chemical stability and antioxidant activity of (−)-epigallocatechin gallate (EGCG) in the gastrointestinal tract, niosomes composed of Tween-60 and cholesterol were developed to encapsulate EGCG in this investigation. EGCG loaded niosomes with encapsulation efficiency around 76% exhibited a small <i>Z</i>-average diameter about 60 nm. Compared to free EGCG, the EGCG remaining in dialysis tubes was significantly improved for niosomes at pH 2 and 7.4. Meanwhile, the residual EGCG for niosomes increased from 3% to 49% after 2 h incubation in simulated intestinal fluid (SIF). Pancreatin was found to impact the stability of niosomes in SIF mainly. Furthermore, the results from ferric reducing antioxidant power and cellular antioxidant activity tests indicated that EGCG loaded niosomes exhibited stronger antioxidant ability than free EGCG during intestinal digestion. Thus, we can infer that niosomal encapsulation might be a promising approach to improve the oral bioavailability of EGCG in the body

Exploring the Binding of Barbital to a Synthetic Macrocyclic Receptor. A Charge Density Study

Experimental charge density distribution studies, complemented by quantum mechanical theoretical calculations, of a host–guest system composed of a macrocycle (<b>1</b>) and barbital (<b>2</b>) in a 1:1 ratio (<b>3</b>) have been carried out via high-resolution single-crystal X-ray diffraction. The data were modeled using the conventional multipole model of electron density according to the Hansen–Coppens formalism. The asymmetric unit of macrocycle <b>1</b> contained an intraannular ethanol molecule and an extraannular acetonitrile molecule, and the asymmetric unit of <b>3</b> also contained an intraannular ethanol molecule. Visual comparison of the conformations of the macrocyclic ring shows the rotation by 180° of an amide bond attributed to competitive hydrogen bonding. It was found that the intraannular and extraannular molecules inside were orientated to maximize the number of hydrogen bonds present, with the presence of barbital in <b>3</b> resulting in the greatest stabilization. Hydrogen bonds ranging in strength from 4 to 70 kJ mol^–1 were the main stabilizing force. Further analysis of the electrostatic potential among <b>1</b>, <b>2</b>, and <b>3</b> showed significant charge redistribution when cocrystallization occurred, which was further confirmed by a comparison of atomic charges. The findings presented herein introduce the possibility of high-resolution X-ray crystallography playing a more prominent role in the drug design process