Bing-Nan Zhou

Structure and stereochemistry of a novel bioactive sphingolipid from a Calyx sp.

Abstract Bioassay-directed fractionation of a sponge of the genus Calyx using a yeast bioassay for DNA-damaging agents yielded the novel sphingolipid calyxoside (1) as the major bioactive constituent. The structure of 1 was assigned as 1,3,26-trihydroxy-2,27-diaminooctacosan-18-one-1-β- d -glucoside by 1H- and 13C NMR, DEPT, DQCOSY, HMQC, and HMBC spectra. The carbonyl group was located at C-18 by analysis of the EI-MS fragmentation of the amino derivative of its aglycone pentaacetate. Its absolute configuration was determined as 2S,3R,26S,27S by analysis of the 1H NMR and CD spectra of its aglycone pentabenzoate.

New Cytotoxic Manzamine Alkaloids from a Palaun Sponge

A crude extract of a marine sponge showed initial inhibitory bioactivities in a yeast assay for inhibitors of methionine amino- peptidase-2 (Met AP-2). Bioassay-directed fractionation indicated that the activity was concentrated in the CH2Cl2-soluble fraction, and chromatography on silica gel led to the isolation of the two new bioactive alkaloids N-methyl-epi-manzamine D 1 and epi-manzamine D 2. The structures of the epi-manzamines were assigned by 1 H and 13 C NMR, DEPT, HMQC, and HMBC spectroscopy, and by comparison with the spectra of related compounds, and the structure of 1 was confirmed by X-ray structure analysis. Neither of the two isolated compounds showed selectivity in the yeast assay for inhibitors of Met AP-2, but both compounds were cytotoxic to HeLa and B16F10 mammalian cells, with compound 1 showing strong activity against the B16F10 cell line. q 2000 Elsevier Science Ltd. All rights reserved. Angiogenesis, or the development of new blood vessels, is an essential requirement of solid tumor growth, and it has been proposed to be the rate-limiting factor for tumor growth; angiogenesis inhibitors could thus play an impor- tant role in cancer chemotherapy.The antiangiogenic agent fumagillin has been shown to target methionine aminopep- tidase type 2 (Met AP-2); the related enzyme Met AP-1 is not affected by fumagillin. 1,2 Yeast strains are available with the genes for both Met AP-1 and Met AP-2 deleted; 3 compounds that act in the same way as fumagillin will be selective inhibitors of Met AP-2, and will thus show a greater growth inhibition for yeasts lacking Met AP-1 than for those lacking Met AP-2. 1 The differential sensitivity of Dmap1 and Dmap2 strains of yeast thus provides a tool for screening for angiogenesis inhibitors in plant extracts.

DNA damaging activities of methanol extract of Ajuga postii and iridoid glucoside reptoside.

An iridoid glucoside reptoside (1) has been isolated as a DNA damaging active agent by bioassay-guided fractionation of the methanol extract of Ajuga postii. Furthermore, from the acetone extract of A. postii two known triterpenic compounds ursolic acid, α-amyrin and two steroidal compounds (24S)-24-ethylcholesta-5,25-dien-3β-ol and β-sitosterol were isolated. Their structures were elucidated based on 1D and 2D NMR techniques and mass data.