Two new polyhydroxysteroids from the gorgonian Isis hippuris

Two new polyhydroxysteroids isihippurols A (1) and B (2) were isolated from the MeOH extract of the gorgonian Isis hippuris in addition to nine known steroids namely gorgosterol, 3alpha-acetoxy-24-methyl 11beta,18; 18,20beta; 22,25-triepoxy-5alpha-furostane, hippurin-1, 22-epi-hippuristanol, 22-epi-hippurin-1, 3-acetyl-2-deacetyl-22-epi-hippurin-1, 2-deacetylhippurin-1, 3beta, 7alpha, 11alpha-trihydroxygorgost-5-ene-12beta-acetate and 2-deacetyl-22-epi-hippurin-1. The structures of 1 and 2 have been determined as 1alpha, 3beta, 5alpha, 6beta, 11alpha-pentahydroxygorgosta-12beta-monoacetate and 1alpha, 3beta, 11alpha-trihydroxygorgosta-5alpha, 6alpha-epoxy-12beta-monoacetate respectively by spectral analysis and chemical correlation.

Taxane diterpenoids from the stem bark of Taxus mairei

Three new 11(15-->1)-abeo-taxanes, taxumairols U-W (1-3), have been isolated from extracts of the stem bark of Formosan Taxus mairei. The structures of 1-3 were identified as 5alpha,7beta,9alpha,13alpha,20-pentaacetoxy-2alpha,10beta,15-trihydroxy-11(15-->1)-abeo-taxene, 5alpha,7beta,9alpha,20-tetraacetoxy-2alpha,10beta,13alpha,15-tetrahydroxy-11(15-->1)-abeo-taxene, and 2alpha,4alpha,7beta,10beta-tetraacetoxy-5beta,20-epoxy-9alpha,13alpha,15-trihydroxy-11(15-->1)-abeo-taxene, respectively, on the basis of 2D NMR techniques including COSY, HSQC, HMBC, and NOESY experiments as well as chemical reactions of compounds 1-3 to give 4 (5alpha,7beta,9alpha,10beta,13alpha,20-hexaacetoxy-2alpha,15-dihydroxy-11(15-->1)-abeo-taxene) and 5 (4alpha,7beta,10beta-triacetoxy-9alpha,13alpha-dibenzoxy-5beta,20-epoxy-2alpha,15-dihydroxy-11(15-->1)-abeo-taxene), which are also novel taxane derivatives. Taxumairols U (1) and V (2) exhibited significant cytotoxicities against human hepatoma tumor cells, while taxumairol W (3) was inactive.

Three new furan derivatives and a new fatty acid from a Taiwanese marine sponge Plakortis simplex

Three new furan derivatives, plakorsins A-C (6-8), together with a new fatty acid, plakortic acid (9), have been isolated from the Taiwanese marine sponge Plakortis simplex in addition to the known metabolites chondrillin (1), 6-epi-chondrillin (2), 2-oxo-2,5-dihydrofuran-5-acetic acid methyl ester (methyl 1,4-epoxy-1-oxo-2-hexenoate) (3), dimethyl beta-ketoadipate (4), and the monomethyl ester of cis,cis-muconic acid (5). The structures of these compounds were established mainly on the basis of spectral data and chemical methods. Biological studies revealed that compound 7 exhibited cytotoxic activity against COLO-250 and KB-16 cells, and compound 1 is active against KB-16 cells.

Two new acetylenic derivatives and a new meroditerpenoid from a Taiwanese marine sponge Strongylophora durissima

Further chemical examination of the sponge Strongylophora durissima yielded two new acetylenic derivatives, durissimols A (1) and B (2), and a new meroditerpenoid, strongylophorine-12 (5), in addition to the known acetylenic compounds, reneirin-2 (3), 18-hydroxyreneirin-2, melyne-C (4), duryne, siphanochalynol, and 24-ethylcholesterol (7). Among them, durissimol B (2) and duryne showed potent cytotoxicity against human gastric tumor (NUGC) cells.

Digital simulation of the membrane voltages and currents in nerve and muscle fibers

This paper describes digital computer simulations of the membrane voltages and currents in axons and muscle fibers. The simulations, which allow calculations ona nonuniform fiber, are based on the discrete Hodgkin-Huxley and Falk-Fatt equations. An efficient algorithm is used to solve the set of equations generated. Calculations are made of the voltage and current at the natural end of a muscle fiber and the results are compared with measurements by other investigators.