New Steroidal Saponins from the Leaves of Yucca elephantipes

Two new spirostanol saponins, namely elephanosides G and H ( 1 and 2 , resp.) were isolated from the leaves of Yucca elephantipes (Agavaceae), together with the two known furostanol saponins 3 and 4 and the six known flavonoid O‐ and C‐glycosides 5 – 10 . The new structures were elucidated as (3β,25S)‐spirost‐5‐en‐3‐yl O‐β‐D ‐glucopyranosyl‐(1→3)‐O‐β‐D ‐glucopyranosyl‐(1→4)‐β‐D ‐galactopyranoside ( 1 ) and (3β,5β,25R)‐3‐[(2‐O‐β‐D ‐glucopyranosyl‐β‐D ‐galactopyranosyl)oxy]spirostan‐12‐one ( 2 ) on the basis of detailed spectroscopic analysis and acidic hydrolysis.     

Nonylphenol Polyethoxylates Degraded by Three Different Wavelengths of UV and Their Genotoxic Change—Detected by Generation of γ‐H2AX

UV rays in sunlight are an important factor in the degradation of chemicals. In this study, we investigated the degradation of nonionic surfactants, nonylphenol polyethoxylates (NPEOs) with 10 or 70 ethylene oxide (EO) units using UVA, B and C, and their genotoxic change based on phosphorylation of histone H2AX (γ‐H2AX), a marker of DNA damage. NPEOs were degraded dependent on the energy of UV, that is, UVC having the highest energy was most effective, whereas UVA having the lowest energy caused little change. The EO side chain of NPEO(70) was broken near the benzene ring by UV, producing NPEOs with a shortened EO chain (around 10 units). The generation of γ‐H2AX reflected the pattern of degradation; shortening of the EO chain changed NPEO(70) into an inducer for γ‐H2AX, and degradation of NPEO(10) attenuated the genotoxicity. The γ‐H2AX generated by NPEO(10) and UV‐degraded NPEO(70) was independent of the cell cycle. The formation of DNA double strand breaks detected by gel electrophoresis was consistent with the results for γ‐H2AX. These results suggested that UV rays can make NPEOs harmless or genotoxic according to the degradation of the EO side chain, the effects being dependent on wavelength.     

Highly Efficient Synthesis of Tricyclic Perimidines under Microwave Heating

A new and efficient access to (Z)‐N‐(2‐argio‐1‐(1H‐perimidin‐2‐yl)vinyl)benzamide derivatives from readily available substrates in HOAc is described with aid of microwave irradiation. The results of our study provide a simple, straightforward synthetic route to these interesting classes of 2‐substituted perimidines analogs in excellent yields.     

Unusual annulation reaction of electron-deficient alkenes with enamines: an easy access to stereocontrolled 4-fluoroalkylated 3,4-dihydro-2H-pyrans

The reaction of β-fluoroalkylated α,β-unsaturated ketones with various enamines gave 4-fluoroalkylated 3,4-dihydro-2H-pyrans as a major product in good yields by a one-pot operation, and these products display the high diastereoselection just after single recrystallization. This unexpected result is rationalized by the unique reactivity of β-fluoroalkylated α,β-unsaturated ketones. As the synthetic application, 4-trifluoromethyl tetrahydropyran was synthesized in moderate isolated yield with high diastereoselectivity.     

Synthesis of novel 4′-C-methyl-1′,3′-dioxolane pyrimidine nucleosides and evaluation of its anti-HIV-1 activity

The key glycosyl donor for the target molecule 12 was prepared by two-step sequences; (1) acetalization of tert-butyldimethylsilyloxyacetaldehyde with 3-bromopropanediol, (2) DBN-initiated β-elimination of the resulting 2-(tert-butyldimethylsilyloxy)methyl-4-bromomethyl-1,3-dioxolane 11. Electrophilic glycosidation between 12 and silylated pyrimidine nucleobase proceeded efficiently to provide a mixture of β- and α-anomers of the respective glycosides 14 and 15. Tin radical-mediated reduction of the bromomethyl functional group of 14 and 15 gave protected 4′-C-methyl-dioxorane uracil- 16 and thymine nucleoside 17. The respective cytosine nucleoside 18 was synthesized from 16. De-silylation of 4′-methyl-1′,3′-dioxolane pyrimidine nucleosides 16–18 gave the target molecules. Evaluation of the anti-HIV-1 activity of the β- and α-anomers of the novel 4′-C-methyl-1′,3′-dioxolane nucleosides 22β,α–24β,α revealed that none of the nucleoside derivatives possess anti-viral activity against HIV-1 and show cytotoxicity against MT-4 cells at 100 μM.     

Spectroscopic Investigation on Sonocatalytic Damage of BSA Molecules by FeIII Complexes with Binary Organic Acid Ligands Under Ultrasonic Irradiation

The interaction between bovine serum albumin (BSA) and Fe^III complexes with three binary organic acid (biorga) ligands, [Fe^III(oxa)(H₂O)₄]⁺ (oxa = oxalic acid), [Fe^III(pra)(H₂O)₄]⁺ (pra = propanedioic acid) and [Fe^III(sua)(H₂O)₄]⁺ (sua = succinic acid), as well as the sonocatalytic damage of BSA in the presence of these three Fe^III–biorga complexes under ultrasonic irradiation, were studied by UV–vis and fluorescence spectra. The experimental results show that the fluorescence quenching process of BSA caused by three Fe^III–biorga complexes are all static quenching and the corresponding quenching rate constants (K _q), equilibrium constants (K _A) and the binding site numbers (n) were calculated. The results reveal that, under ultrasonic irradiation, the BSA molecules were obviously damaged by these Fe^III–biorga complexes. In addition, the effects of several factors on the damage of BSA molecules were examined. The experimental results demonstrate that the damage degree of BSA increased with an increase of ultrasonic irradiation time, Fe^III–biorga complex concentration, and ionic strength. In comparison, [Fe^III(pra)(H₂O)₄]⁺ exhibited higher sonocatalytic activity than [Fe^III(oxa)(H₂O)₄]⁺ and [Fe^III(sua)(H₂O)₄]⁺. Finally, the extent of generation of $ \cdot {\text{O}}_{2}^{ - } $ · O 2 ? and ·OH during sonocatalytic processes was estimated. Perhaps, the results will be significant for promoting sonodynamic treatment (SDT) of tumors at the molecular level.     

Synthesis,Structures, and Luminescent Properties of two 3, 5‐Dimethyl‐1‐H‐1, 2,4‐triazole‐Based Zinc Metal‐Organic Frameworks with Aromatic Carboxylate as Coligand

Two metal‐organic frameworks, [Zn(dmtrz)(btrc)_1/3]_n ( 1 ) and [Zn₂(dmtrz)₂(btec)(H₂O)₂]_n ( 2 ) (dmtrz = 3, 5‐dimethyl‐1‐H‐1, 2,4‐triazole, btrc = 1, 3,5‐benzenetricarboxylate, btec = 1, 2,4, 5‐benzenetetracarboxylate), were synthesized by hydrothermal reaction. The crystal structure analysis reveals that compound 1 is a dense 3D framework with Schläfli symbols of {4³}₂{4⁶ · 6⁶ · 8³}₃, which is a loh1 structure. Compound 2 is a 2D network. In addition, the photoluminescence of two compounds were studied in solid state at room temperature, together with their thermal analysis.     

TargetATPsite: A template‐free method for ATP‐binding sites prediction with residue evolution image sparse representation and classifier ensemble

Understanding the interactions between proteins and ligands is critical for protein function annotations and drug discovery. We report a new sequence‐based template‐free predictor (TargetATPsite) to identify the Adenosine‐5′‐triphosphate (ATP) binding sites with machine‐learning approaches. Two steps are implemented in TargetATPsite: binding residues and pockets predictions, respectively. To predict the binding residues, a novel image sparse representation technique is proposed to encode residue evolution information treated as the input features. An ensemble classifier constructed based on support vector machines (SVM) from multiple random under‐samplings is used as the prediction model, which is effective for dealing with imbalance phenomenon between the positive and negative training samples. Compared with the existing ATP‐specific sequence‐based predictors, TargetATPsite is featured by the second step of possessing the capability of further identifying the binding pockets from the predicted binding residues through a spatial clustering algorithm. Experimental results on three benchmark datasets demonstrate the efficacy of TargetATPsite. © 2013 Wiley Periodicals, Inc.     

The Effects of Alcohol with Different Chain Length on the Phase Equilibria of Nonionic Surfactant System

Addition of alcohol with longer chain length (C₆H₁₃OH, C₈H₁₇OH, and C₁₂H₂₁OH) caused a reduction the cloud point of a commercial nonionic surfactant, Tesgitol (T_15-s-9). The formation of lamellar liquid crystal (LLC) was favored so that isotropic liquid (L₁)-LLC two-phase region became wider with increasing temperature at an appropriate weight ratio of surfactant to alcohol. The isotropic liquid phase/liquid two phase transformation was replaced by a two-phase transformation to isotropic liquid/lamellar liquid crystal at the cloud point for the system without alcohol.