Cytotoxic triterpenes from a Chinese medicine, Goreishi

Bioactivity-guided fractionation of the methanol extract of Goreishi (the feces of Trogopterus xanthipes Milne-Edwards) afforded one new and three known cytotoxic triterpenes, namely, 3-O-cis-p-coumaroyltormentic acid, pomolic acid, 2 alpha-hydroxyursolic acid, and jacoumaric acid. In the course of this investigation, six additional compounds having no cytotoxic activity were isolated, namely, maslinic acid, 3-O-trans-p-coumaroylmaslinic acid, ursolic acid, tormentic acid, euscaphic acid, and a new triterpene, 3-O-trans-p-coumaroyltormentic acid. The structures of the new compounds were established on the basis of X-nucleus-proton correlation with fixed evolution time (XCORFE) and other spectroscopic evidence.     

Luminescent silicon nanocrystal dots fabricated by SiCl4/H2 RF plasma-enhanced chemical vapor deposition

Luminescent nanocrystalline Si dots were fabricated directly on thermally grown SiO₂ at 120°C by conventional RF plasma-enhanced chemical vapor deposition using tetrachlorosilane, SiCl₄ and H₂. As-deposited Si dot exhibits photoluminescence (PL) in the visible region, consisting of two broad bands corresponding to photon energies of 1.38 and 1.48 eV. Storage in air enhances PL and shifts the PL peak energy to higher wavelengths for dots of diameter less than 10 nm. Fourier transform attenuated total reflection absorption spectroscopy (FTIR-ATR) study reveals that the spontaneous oxidation proceeds until saturation after 70 h at dot sizes of 3–5 nm. The relationship between PL intensity, blueshift of PL peak energy, and surface termination species during oxidation indicates that these changes are attributed to the increased density of radiative centers at the Si nanocrystal dot/SiO₂ interface and enhancement of the quantum confinement effect.     

Maximum Number of Contractible Edges on Hamiltonian Cycles of a 3-Connected Graph

 We show that if G is a 3-connected hamiltonian graph of order at least 5, then there exists a hamiltonian cycle C of G such that the number of contractible edges of G which are on C is greater than or equal to . Received: July 31, 2000 Final version received: December 12, 2000 Acknowledgments. I would like to thank Professor Yoshimi Egawa for the help he gave to me during the preparation of this paper.     

Electronic characteristics of sandwich-type lanthanide octaethylporphyrins

The electronic behavior of sandwich-type rare earth octaethylporphyrinates Ln(oep)2 and Ln2(oep)3 (Ln=Ce, Pr and Eu) was characterized by measurements of the UV-vis or near infrared spectra and D.C. conductivity. However, the conductivity values measured at room temperature were distributed in an order of 10-7 to 10-8 S.cm-1 even after the partial oxidation of complex with the complexes with iodine and no remarkable change was observed among the complexes such as LnIV(Por2-)2 (Ln=Ce) and LnIV(Por2-)(Por.-) (Ln=Ce) or Ln2III(Por2-)3 and LnIII2(Por2-)2(Por-).     

Stabilization against initial oxidation using surface segregation of sulfur on Fe(1 0 0)

Surface segregation process of dissolved elements on a Fe(1 0 0) surface and the initial oxidation processes of the sulfur segregated surfaces were studied in situ by AES and RHEED. The surface enrichment of sulfur has formed a c(2×2) superstructure at elevated temperatures. The Fe(1 0 0)c(2×2)-S surface was found to have stabilization effect against initial oxidation. The retardation of oxidation was most enhanced when the sulfur surface concentration reached at the saturation coverage (1/2 ML). The possible physical origins of the stabilization effect are proposed.     

Amphiphile-induced erythrocyte shape change and simultaneous tetraethylammonium ion uptake.

Amphiphile-induced tetraethylammonium ion (TEA+) uptake into human erythrocytes was examined along with cell shape change. A TEA(+)-sensitive electrode was used to determine the amount of uptake. TEA+ was preferentially incorporated into erythrocytes when amphiphiles changed cell shape to an invaginated form. This was contrasted with the release of acetylcholinesterase outside cells which occurred markedly with the amphiphiles, causing the crenated form. It was suggested that the invagination of erythrocyte membrane stimulated the formation of vacuoles, in which TEA+ existing in an external medium was entrapped.     

Analysis of photodecomposition of gaseous chlorobenzene by KrF excimer laser.

Gaseous monochlorobenzene was irradiated with KrF excimer laser (248 nm) under reduced pressure. The photodecomposition was an apparent first order reaction. When the system contained no additive gas, the photolysis was found to give benzene (conversion yield: 49%) in the gas phase and many unidentified products in the solid phase. On the other hand, in the presence of oxygen, carbon dioxide (10%), carbon monoxide (16%), hydrogen chloride (52%) and acetylene (2%) are produced and the peaks shown on the gas chromatogram of the solid phase were effectively suppressed.     

Photooxidation of Troglitazone,a New Antidiabetic Drug *

Troglitazone (CS-045) is a new oral antidiabetic drug reported to be effective in insulin-resistant diabetes and to show antihypertensive effects. Photooxidation of troglitazone gave the quinone and quinone epoxide as the major final stable products. An intermediate observed by NMR spectroscopy was shown to be the hydroperoxydi-enone, which is moderately stable at room temperature. The rate constant of singlet oxygen quenching by troglitazone is 2.14 × 10⁸M^?1s^?1 and the reaction rate constant in acetone-d, is 8.64 × 10, M^?1 s^?1. Only the chroman ring of troglitazone reacts with and quenches singlet oxygen significantly, and its reactivity and products are analogous to those of a-tocopherol. The reactivity of CS-045 toward singlet oxygen is much larger than that of the related compounds lacking the chroman ring.     

M1 states in 58Ni observed by proton inelastic scattering at 65 MeV

Inelastic proton scattering at 65 MeV was used to study 1⁺ states in ⁵⁸Ni. A new 1⁺ state was found at an excitation of 5.166 MeV. The angular distributions for the 1⁺ states at 2.903 and 5.166 MeV were well reproduced by a DWBA calculation under the assumptions of pure $\text{v(}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}\text{and}\text{v(}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$ configurations, respectively. The angular distribution for the previously suggested 1⁺ state at 7.721 MeV was not well discribed by the DWBA calculation with the isoscalar $\text{(}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ wave function. The shape of the angular distribution for the 10.672 MeV, 1⁺ state was well reproduced by the DWBA calculation with the isovector $\text{(}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}{}^{\mathrm{?1}}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}$ wave function.