Hypermonones A-I,New Polyprenylated Acylphloroglucinols from Hypericum monogynum with Multidrug Resistance Reversal Activity

Eleven biogenetically related polyprenylated acylphloroglucinols(PPAPs),including four novel skeletons(1-4)and five new com-pounds(5-9),were isolated from the flowers of Hypericum monogynum.Hypermonones A-D(1-4)represented the first example of a unique dilactone structure containing carbonyl bonded single 5-lactone and tricyclic γ-lactone moieties.Their structures were elucidated by NMR analysis,X-ray crystallography,and ECD calculations.Moreover,we revised the structure of hyperibrin B to hy perm on one I(9)via NMR an alysis,a qua ntum computational chemistry method,and hypothetic bios yn thetic con siderations.Three compounds(5,6,and 9)with significant MDR reversal activity(RF ranging from 61 to 223)were superior to the positive control verapamil(MCF-7/ADR,RF:53;HepG2/ADRz RF:124).Mechanism study for compound 5 indicated that this compound could inhibit the function of P-gp tran sport rather tha n its expressi on,and the possible recog nition mechanism betwee n compo und 5 and P-gp was predicted by molecular docking.

Phase transformation and crystal growth behavior of 8mol%(SmO1.5, GdO1.5, and YO1.5) stabilized ZrO2 powders

Nanocrystalline powders of ZrO_2–8mol%SmO1.5（8Sm SZ）, ZrO_2–8mol%GdO1.5（8Gd SZ）, and ZrO_2–8mol%YO1.5（8YSZ） were prepared by a simple reverse-coprecipitation technique. Differential thermal analysis/thermogravimetry（DTA/TG）, Fourier transform infrared spectroscopy（FTIR）, X-ray diffraction（XRD）, Raman spectroscopy, and high-resolution transmission electron microscopy（HRTEM） were used to study the phase transformation and crystal growth behavior. The DTA results showed that the ZrO_2 freeze-dried precipitates crystallized at 529, 465, and 467°C in the case of 8Sm SZ, 8Gd SZ, and 8YSZ, respectively. The XRD and Raman results confirmed the presence of tetragonal ZrO_2 when the dried precipitates were calcined in the temperature range from 600 to 1000°C for 2 h. The crystallite size increased with increasing calcination temperature. The activation energies were calculated as 12.39, 12.45, and 16.59 k J/mol for 8Sm SZ, 8Gd SZ, and 8YSZ respectively.

Na^+-K^+-ATPase activity of hepatocyte plasma membranes,reversible and irreversible alterations due to bile acids

Background Chenodeoxycholic acid (CDC) is an apolar bile salt and damages hepatocytes, whereas ursodeoxycholic acid (UDC) is a more polar bile salt and protects liver cell against toxic bile salts. We therefore investigated the activity of membrane associated Na + K + ATPase, a coenzyme of the sodium dependent bile salt carrier. Methods Liver plasma membranes (LPM) were isolated from rat livers according to the method of Song et al (J Cell Biol 1969; 41:124). The LPM were incubated with bile salts (TUDC, UDC, TCDC, CDC) in concentrations of 0.1 2 mmol/L for 0 30 minutes at room temperature. To study reversibility of the effect of CDC, LPM were diluted with buffer 50 times of volume after incubation. The activity of membrane associated Na + K+ ATPase was determined enzymatically at 37℃ and the phospholipid (PL) release into the supernatant was measured. Results CDC and TCDC both showed a dose dependent inhibition of the enzyme activity (P<0.01 vs control). Gastroenterology, Center of Internal Medicine, University Hospital, D 60590 Frankfurt Main, Germany (You T, Guldutuna S, Bhatti S and Leuschner U)Initially TCDC induced an increase in enzyme activity at concentrations of 0.1 1 mmol/L, however, after 3 minutes activity repidly decreased to less than 30% of controls. Up to a concentration of 1 mmol/L CDC the inhibition of enzyme activity could be reversed by diluting the bile salt in the incubation medium. At a concentration of 2 mmol/L CDC activity was only partially restored and at this concentration a marked PL release into the supernatant was observed, indicating solubilization of the membranes. UDC did not decrease the enzyme activity at concentrations of 0.1 2 mmol/L. At a concentration of 2 mmol/L TUDC inhibited the Na + K + ATPase by about 20%. Solubilization of membrane PL was not observed. Conclusion CDC and TCDC inhibited Na + K + ATPase. Dilution of the bile salt with buffer reversed the inhibitory effect up to concentrations of 1 mmol/L CDC. The inhibitory effect is probably due to alteration of the plasma membrane. 2 mM CDC caused irreparable membrane damage. Physiological concentrations of UDC and TUDC did not affect membrane ATPase.

Novel thioxanthone host material with thermally activated delayed fluorescence for reduced efficiency roll-off of phosphorescent OLEDs

2,7-Di（9,9-dimethyl-9H-fluoren-l-yl）-9H-thioxanthen-9-one （DMBFTX） with thermally activated delayed fluorescence （TADF） was well designed and synthesized. The phosphorescent organic lightemitting device （PHOLED） based on this novel TADF host material displays a stable red phosphorescence region, a peak external quantum efficiency （EQE） value of 12.9% and a low EQE roll-off of 38.8%at a luminance of 10000 cd/m2, which is benefited from the reverse intersystem crossing （RISC） of TADF host and less populated triplet exitons. Notably, the red device based on the TADF host DMBFrX exhibits superior electroluminescence performance and reduced efficiency roll-offcompared with the one hosted by commercially available host 1,3-bis（9-carbazolyl）benzene （mCP）, illustrating the high potential of employing the TADF host material with small energy gap to reduce efficiency roll-off in PHOLED.

Rational design of FLP catalysts for reversible H_2 activation: A DFT study of the geometric and electronic effects

Frustrated Lewis pairs（FLPs） emerge as a new type of bifunctional metal-free catalysts for reversible H_2 activation, which is important for the storage and liberation of H_2 or further controllable utilizing chemical fuels via hydrogenation/dehydrogenation. Herein, a DFT study was conducted to understand the geometric factors and electronic effects of FLPs on reversible H_2 activation. The Lewis base group mainly contributes to the proton attachment, and influences the kinetics of the H_2 activation. The Lewis acid group mainly relates to the hydride attachment, and affects more significantly on the thermodynamics of H_2 activation. The dimer and quenched structure of FLPs also have a degree of influence on the performance of catalyzed H_2 activation. A series of FLPs with para-substituted phenyl derivatives as LA groups were designed and evaluated. The results indicate that the variation of LA groups has significant impact on thermodynamic energy of dihydrogen adducts but insignificant effect on kinetics. Moreover,we found the thermodynamic energy of products has a good linear relationship with Hammett substituent constants. The solvent effect on H_2 activation was also studied, and polar solvent is beneficial for zwitterionic products. These results should provide deeper insight to understand the relation between FLPs structure and reactivity, which is critical for rational design of more efficient FLPs catalysts for reversible H_2 activation.