Conformationally constrained, stable, triplet ground state (S = 1) nitroxide diradicals. Antiferromagnetic chains of S = 1 diradicals

Nitroxide diradicals, in which nitroxides are annelated to m-phenylene forming tricyclic benzobisoxazine-like structures, have been synthesized and characterized by X-ray crystallography, magnetic resonance (EPR and 1H NMR) spectroscopy, as well as magnetic studies in solution and in solid state. For the octamethyl derivative of benzobisoxazine nitroxide diradical, the conformationally constrained nitroxide moieties are coplanar with the m-phenylene, leading to large values of 2J (2J/k > 200 K in solution and 2J/k > 300 K in the solid state). For the diradical, in which all ortho and para positions of the m-phenylene are sterically shielded, distortion of the nitroxide moieties from coplanarity is moderate, such that the singlet-triplet gaps remain large in both solution (2J/k > 200 K) and the solid state (2J/k approximately 400-800 K), though an onset of thermal depopulation of the triplet ground state is detectable near room temperature. These diradicals have robust triplet ground states with strong ferromagnetic coupling and good stability at ambient conditions. Magnetic behavior of the nitroxide diradicals at low temperature is best fit to the model of one-dimensional S = 1 Heisenberg chains with intrachain antiferromagnetic coupling. The antiferromagnetic coupling between the S = 1 diradicals may be associated with the methyl nitroxide C-H- - -O contacts, including nonclassical hydrogen bonds. These unprecedented organic S = 1 antiferromagnetic chains are highly isotropic, compared to those of the extensively studied Ni(II)-based chains.     

Design of Turmeric Rhizome Extract Nano-Formula for Delivery to Cancer Cells

Novel turmeric rhizome extract nanoparticles (TE-NPs) were developed from fractions of dried turmeric (Curcuma longa Linn.) rhizome. Phytochemical studies, by using HPLC and TLC, of the fractions obtained from ethanol extraction and solvent–solvent extraction showed that turmeric rhizome ethanol extract (EV) and chloroform fraction (CF) were composed mainly of three curcuminoids and turmeric oil. Hexane fraction (HE) was composed mainly of turmeric oil while ethyl acetate fraction (EA) was composed mainly of three curcuminoids. The optimal TE-NPs formulation with particle size of 159.6 ± 1.7 nm and curcumin content of 357.48 ± 8.39 µM was successfully developed from 47-run D-optimal mixture–process variables experimental design. Three regression models of z-average, d₅₀, and d₉₀ could be developed with a reasonable accuracy of prediction (predicted r² values were in the range of 0.9120–0.9992). An in vitro cytotoxicity study using MTT assay demonstrated that the optimal TE-NPs remarkably exhibited the higher cytotoxic effect on human hepatoma cells, HepG2, when compared with free curcumin. This study is the first to report nanoparticles prepared from turmeric rhizome extract and their cytotoxic activity to hepatic cancer cells compared with pure curcumin. These nanoparticles might serve as a potential delivery system for cancer therapy.     

Bioactive prenylated xanthones and anthraquinones from Cratoxylum formosum ssp. pruniflorum

Ten new compounds (1-10), pruniflorone A-J, together with 21 known compounds (11-31) were isolated from the roots and barks of Cratoxylum formosum ssp. pruniflorum. Their structures were determined by spectroscopic methods. Compounds 1 and 11 were also confirmed by X-ray diffraction data. In addition, antibacterial and cytotoxic activities of the isolates were also evaluated.     

1-Acetyl-3-[benzoyl(4-methoxy­phenyl)­methyl­ene]-2,3-di­hydro-1H-indol-2-one

In the title compound, C₂₅H₁₉NO₄, the indole moiety is not completely planar, the heterocyclic ring being distorted very slightly towards a half-chair conformation. The benzoyl and 4-­methoxy­phenyl substituents are individually almost planar and are in a bisecting and nearly perpendicular configuration, respectively, with respect to the plane of the indole moiety. The molecular and packing structures in the crystal are stabilized by intramolecular and intermolecular C—H⋯O interactions.     

Electrospun fiber mats of poly(3‐hydroxybutyrate), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), and their blends

Electrospinning of poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), and their blends was first carried out in chloroform at 50 °C on a stationary collector. The average diameter of the as‐spun fiber from PHB and PHBV solutions decreased with increasing collection distance and increased with increasing solution concentration and applied electrical potential. In all of the spinning conditions investigated, the average diameter of the as‐spun pure fibers ranged between 1.6 and 8.8 μm. Electrospinning of PHB, PHBV, and their blends was carried out further at a fixed solution concentration of 14% w/v on a homemade rotating cylindrical collector. Well‐aligned, cross‐sectionally round fibers without beads were obtained. The average diameter of the as‐spun pure and blend fibers ranged between 2.3 and 4.0 μm. The as‐spun fiber mats appeared to be more hydrophobic than the corresponding films and much improvement in the tensile strength and the elongation at break was observed for the blend fiber mats over those of the pure fiber ones. Lastly, indirect cytotoxicity evaluation of the as‐spun pure and blend fiber mats with mouse fibroblasts (L929) indicated that these mats posed no threat to the cells. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2923–2933, 2006