Medicinal flowers. XXIII. New taraxastane-type triterpene, punicanolic acid, with tumor necrosis factor-alpha inhibitory activity from the flowers of Punica granatum

The methanolic extract from the flowers of Punica granatum L. (Punicaceae) was found to show inhibitory effect on tumor necrosis factor-alpha (TNF-alpha, 1 ng/ml)-induced cytotoxicity in L929 cells. By bioassay-guided separation, a new taraxastane-type triterpene, punicanolic acid (1), was isolated from the active fraction (ethyl acetate-soluble fraction) together with four triterpenes (2--5), two galloyl glucoses (6, 7), two flavones (8, 9), and beta-sitosterol. Among the constituents, 1, oleanolic acid (2), maslinic acid (4), 1,2,6-tri-O-galloyl beta-D-glucopyranoside (6), 1,2-di-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl beta-D-glucopyranoside (7), and luteolin (8) significantly inhibited TNF-alpha-induced cytotoxicity in L929 cells at 30 microM.     

Near-field two-photon-induced photoluminescence from single gold nanorods and imaging of plasmon modes

We investigated the two-photon-induced photoluminescence properties of single gold nanorods by scanning near-field spectroscopy. The process was found to be initiated by a sequential one-photon absorption for creating a pair of an electron and a hole in the sp and d bands. Photoluminescence is then radiated when the electron near the Fermi surface recombines with the hole near the X and L symmetry points. The polarization characteristics of emitted photons from the X and L regions were found to be different. These characteristics can be understood by the crystalline structure and the band structure of the gold nanorod. We found characteristic spatial oscillatory features along the long axis of the nanorods in photoluminescence excitation images. The images were well reproduced by density-of-states maps of the nanorods calculated with Green's dyadic method and were attributed to the spatial characteristics of the wave functions of the plasmon modes inside the nanorods.     

Impurity effects of some metals on electrical properties of amorphous As2Se1Te2 films

Amorphous As₂Se₁Te₂ (a-As₂Se₁Te₂) films, into which Cu or Cd ions were doped by thermal diffusion below the glass transition temperature exhibited the increase of conductivity by several orders of magnitude. In addition, these samples exhibited enhanced photoconductivity and the activation type conduction. From the measurements of the thermoelectric power, it was found that Cu doped samples were p-type and Cd doped samples were n-type. The impurities was also studied by SIMS.     

Novel preparation of ion-supported triphenylphosphines and their synthetic utility

Novel ion-supported Ph₃P compounds, 4-(diphenylphosphino)- benzyltrimethylammonium bromide (A) and N-methyl-N-[4-(diphenylphosphino) -benzyl]pyrrolidinium bromide (B), were prepared. Because of their stability in air, ion-supported Ph₃P A and B could be used for the halogenation of alcohols, the esterification of carboxylic acid with the Mitsunobu reaction, the Mizoroki-Heck reaction, and the Sonogashira reaction. The advantages of using these ion-supported Ph₃P A and B are the simple isolation of the products by ether extraction due to their poor solubility in ether, and the easy recovery of the co-product, ion-supported Ph₃PO, by filtration in high yields (>90%), which could be regenerated and reused for the same reactions, in the halogenation of alcohols and the esterification of carboxylic acid with the Mitsunobu reaction. On the other hand, ionic liquid reaction media containing Pd(OAc)₂ or PdCl₂ and ion-supported Ph₃P A or B as catalysts could be reused for the same Mizoroki-Heck reaction and the Sonogashira reaction maintaining high yields, using iodotoluene with methyl acrylate and phenylacetylene, respectively.     

Reversible phase transfer and fractionation of Au nanoparticles by pH change

The reversible transfer of Au nanoparticles between water and chloroform phases by pH change was achieved by using a long-chain amine derivative. Further, we demonstrated that the phase transfer method was very effective for the fractionation of Au nanoparticles according to their crystal facet distinction.     

Scavenging effects of metal complexes of water-soluble thiacalix[4]arenetetrasulfonate on superoxide anion radicals

The scavenging effects of metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4], Me=H?, Fe3(+), Mn3(+), Mn2(+), Cu2(+), and Zn2(+)) on superoxide anion radicals (O??) generated from the xanthine-xanthine oxidase system were investigated by the nitroblue tetrazolium (NBT) method and electron spin resonance (ESR) spin-trapping method using 5,5-dimethyl-1-pyrroline-N-oxide as a trapping reagent. As a reference, calix[4]arenetetrasulfonate (H?)-CAS[4]), calix[6]arenehexasulfonate (H?-CAS[6]) and calix[8]areneoctasulfonate (H?-CAS[8]) were also examined. The results by the NBT method indicated that Fe3(+)- and Mn3(+)-TCAS[4] exhibited the highest O?? scavenging activity among Me-TCAS[4] and H?-CAS[n] (n = 4, 6, 8) in this study. The IC?? values of Fe3(+)- and Mn3(+)-TCAS[4] for O?? scavenging activity were estimated to be 5.3 and 7.8 μM, respectively, and were almost the same as those of tannin acid, catechin and their derivatives, which are known as very effective scavengers of O??. Scavenging activities were in the order of Fe3(+)- and Mn3(+)-TCAS[4]>Mn2(+)-, Cu2(+)-, and Zn(2+)-TCAS[4]>H(2)-TCAS[4] and H?-CAS[n] (n=4, 6, 8). Each activity of Me-TCAS[4] (Me=Fe3(+), Mn3(+), Mn2(+), Cu2(+), and Zn2(+)) was higher than that of the corresponding metal ion, indicating that H?-TCAS[4] has the ability to raise the activity of the metal ion itself by forming a complex. Also, the ESR spin-trapping method revealed that Fe3(+)- and Mn3(+)-TCAS[4] showed high O?? scavenging activities, similarly to the results by the NBT method.     

Amorphous silicon diamond based heterojunctions with high rectification ratio

We have fabricated and characterized diamond based heterojunctions composed of homoepitaxial diamond (B-doped film: p type) and hydrogenated amorphous silicon (a-Si:H film: n-type). All devices include an intrinsic amorphous silicon interface (i-a-Si:H). (J–V) characteristics of a-Si:H heterojunctions measured from 300 K to 460 K present a very high rectification ratio (in the range 10⁸–10⁹) and a current density of 10 mA/cm² under 2 V of forward bias. The reverse current up to ? 4 V is below the detection limit in the whole temperature range. The devices present two regimes of operation indicating that more than one mechanism governs the carrier transport. These characteristics are compared with a Schottky barrier diode (SBD) using a tungsten carbide metal on top of the p-type diamond as a Schottky contact. The SBD device exhibits J–V characteristic with an ideality factor n close to one and the heterojunction follows this trend for low bias voltages whereas for bias voltage above 1 V a second regime with larger ideality factors n ~ 3.6 is observed. These results point out the prominent role of transport mechanisms at heterointerface between the a-Si:H layers and the p-type doped diamond which degrades the current injection. The breakdown voltage reached ? 160 V indicating the good quality of the deposited layers.     

Displacement Plating of a Mesoporous Pt Skin onto Co Nanochains in a Low‐Concentration Surfactant Solution

Mesoporous Pt skins on Co nanochains are successfully synthesized by a displacement reaction between Pt species and a Co support with the assistance of surfactant micelles. The assembly of surfactant micelles on Co nanochains plays a key role in the formation of mesoporous Pt layers. The evolution of the mesoporous Pt layers is carefully studied at different time intervals. As the reaction time increases, the mesoporous Pt layers become thicker, and well‐defined mesoporous structures gradually develop. The obtained mesoporous Pt skin exhibits high activity and superior CO tolerance in the electro‐oxidation reaction of methanol. The mesoporous Pt skin also shows very high durability, and only a 20.2 % loss of the Pt electrochemical surface area is found even after a harsh durability test.     

Electric Double‐Layer Capacitors Based on Highly Graphitized Nanoporous Carbons Derived from ZIF‐67

Nanoporous carbons (NPCs) have large specific surface areas, good electrical and thermal conductivity, and both chemical and mechanical stability, which facilitate their use in energy storage device applications. In the present study, highly graphitized NPCs are synthesized by one‐step direct carbonization of cobalt‐containing zeolitic imidazolate framework‐67 (ZIF‐67). After chemical etching, the deposited Co content can be completely removed to prepare pure NPCs with high specific surface area, large pore volume, and intrinsic electrical conductivity (high content of sp²‐bonded carbons). A detailed electrochemical study is performed using cyclic voltammetry and galvanostatic charge–discharge measurements. Our NPC is very promising for efficient electrodes for high‐performance supercapacitor applications. A maximum specific capacitance of 238 F g^?1 is observed at a scan rate of 20 mV s^?1. This value is very high compared to previous works on carbon‐based electric double layer capacitors.