No abstract

Ustiloxins A (la), B (lb), C (lc), D (Id) and E (le), antimitotic peptides, have been isolated from the water extract offalse smut balls caused on the panicles of rice plant by a fungus Ustilaginoidea virens. The structure of lb was assigned from its spectral property and its aminoacid analysis in relation to la whose structure was determined previously by a conbination of X-ray crystallographic and amino acid analyses. Structures of lc and Id were elucidated by their spectroscopic data, specially based on their *H and 13C NMR spectra. Bioactivities of these compoundsagainst microtubule assembly as well as manmal, plant and fungal cells have been studied.The false smut balls growing parasitically on panicles of rice plant (in Japanese, Ina-kouji) are caused by a pathogen, Ustilaginoidea virens Cooke, Takahashi. It has been reported that the panicles suffered from this disease has poor crops and that occasional injection of such rice plants caused poisoning to the domestic animals.

The neutron-rich carbon isotopes 19,17C have been investigated via proton inelastic scattering on a liquid hydrogen target at 70 MeV/nucleon. The invariant mass method in inverse kinematics was employed to reconstruct the energy spectrum, in which fast neutrons and charged fragments were detected in coincidence using a neutron hodoscope and a dipole magnet system. A peak has been observed with an excitation energy of 1.46(10) MeV in 19C, while three peaks with energies of 2.20(3), 3.05(3), and 6.13(9) MeV have been observed in 17C. Deduced cross sections are compared with microscopic DWBA calculations based on p-sd shell model wave functions and modern nucleon-nucleus optical potentials. Jpi assignments are made for the four observed states as well as the ground states of both nuclei.Comment: 20 page

We have studied the antitumor activity and the novel DNA‐self‐strand‐breaking mechanism of CNDAC (1‐(2‐C‐cyano‐2‐deoxy‐β‐d‐arabino‐pentofuranosyl)cytosine) and its N4‐palmitoyl derivative (CS‐682). In vitro, CS‐682 showed strong cytotoxicity against human tumor cells comparable with that of CNDAC; both compounds displayed a similar broad spectrum. In vivo, however, orally administered CS‐682 showed a more potent activity against human tumor xenografts than CNDAC, 5′‐deoxy‐5‐fluorouridine, 5‐fluorouracil and 2′,2′‐difluorodeoxycytidine. Moreover, CS‐682 was effective against various human organ tumor xenografts at a wide dose range and with low toxicity, and was effective against P388 leukemic cells resistant to mitomycin‐C, vincristine, 5‐fluorouracil or cisplatin in syngeneic mice. CNDAC, an active metabolite of CS‐682, had a prolonged plasma half‐life after repeated oral administrations of CS‐682 but not after oral administrations of CNDAC itself. This difference may partially explain the higher antitumor activity of CS‐682 relative to CNDAC. In both CNDAC‐ and CS‐682‐treated carcinoma cells, CNDAC 5′‐triphosphate (CNDACTP) was generated and incorporated into a DNA strand. High performance liquid chromatography (HPLC) and mass spectrometric analysis of the nucleosides prepared by digestion of the DNA from the CNDAC‐treated cells detected ddCNC (2′‐C‐cyano‐2′,3′‐didehydro‐2′,3′‐dideoxycytidine), which was shown to be generated only when the self‐strand‐breakage of CNDACTP‐incorporated DNA occurred. The cytotoxicity of CNDAC was completely abrogated by the addition of 2′‐deoxycytidine and was low against cells with decreased deoxycytidine kinase. Our results suggest that CNDAC is converted to CNDACMP by deoxycytidine kinase and that the resulting CNDACTP incorporated into a DNA strand as CNDACMP may induce DNA‐self‐strand‐breakage. This novel DNA‐self‐strand‐breaking mechanism may contribute to the potent antitumor activity of CS‐682. Int. J. Cancer 82:226–236, 1999. © 1999 Wiley‐Liss, Inc.

Novel scalarane sesterterpenes (1-4) were isolated from a sponge, Hyrtios erecta (order Dictyoceratida). They were characterized by means of spectral analyses, X-ray crystallography, and chemical reactions. Compound 1 showed potent in vitro and in vivo antitumor activities. In addition, the structure-activity relationship was also discussed using computer-assisted structure matching of 1 and aragusterols.