Yoshiaki Takaya

Scabronines B, C, D, E and F, novel diterpenoids showing stimulating activity of nerve growth factor-synthesis, from the mushroom Sarcodon scabrosus

Abstract Novel cyathane-type diterpenoids, scabronines B – F (1 – 5) were isolated from the mushroom Sarcodon scabrosus . Their structures were determined by interpretation of their spectral data and chemical transformation. The absolute stereochemistry of scabronine C (2) was confirmed by the exciton chirality method, and the chemical transformation of scabronines B, C and D (1, 2 and 3) clarified their absolute structures. The absolute stereochemistries of scabronines E and F (4 and 5) were determined by comparison of their CD spectra with that of erinacine A (7). Among these compounds, scabronines B, C and E (1, 2 and 4) exhibit stimulating activity of the synthesis of a nerve growth factor.

Scabronine A, a novel diterpenoid having potent inductive activity of the nerve growth factor synthesis, isolated from the mushroom, Sarcodon scabrosus

Abstract A novel diterpenoid, scabronine A, having strong inductive activity of the nerve growth factor synthesis was isolated from the fruit body of the mushroom, Sarcodon scabrosus (Fr.) Karst. The stereostructure of scabronine A ( 1 ) was elucidated on the basis of the spectroscopic analysis of natural scabronine A and its derivatives.

NEW OLIGOSTILBENES HAVING A BENZOFURAN FROM VITIS VINIFERA 'KYOHOU'

Abstract Three new oligostilbenes having a benzofuran moiety, viniferifuran, (+)-vitisifuran A and (−)-vitisifuran B, were isolated from Vitis vinifera ‘Kyohou’. The structures of these oligostilbenes including the absolute configuration were elucidated by spectroscopic and chemical methods. Furthermore, these were chemically transformed from (+)-e-viniferin, (+)-vitisin A and (−)-vitisin B, respectively, whose absolute configurations are known.

Absolute configurations of some oligostilbenes from Vitis coignetiae and Vitis vinifera ‘Kyohou’

Abstract Hepatotoxic oligostilbenes, (+)-vitisin A and (+)- cis -vitisin A were isolated as a pure form, respectively, by the method of recycled HPLC. The structure of cis -vitisin A was confirmed by the photochemical transformation of vitisin A. The absolute configurations of (+)-ampelopsin A, (+)-ampelopsin B, (+)-vitisin A, (+)- cis -vitisin A and (+)-vitisin D were also determined by chemical and spectroscopic methods.

Novel antimalarial guaiane-type sesquiterpenoids from Nardostachys chinensis roots

Abstract Three guaiane-type sesquiterpenoids, nardoperoxide (1a), isonardoperoxide (2a) and nardoxide (3), were isolated from Nardostachys chinensis roots. Their structures were elucidated by spectral means. Among them, two endoperoxides, nardoperoxide (1a) and isonardoperoxide (2a), showed strong antimalarial activity against Plasmodium falciparum malaria (EC50 1.5 × 10−6 and 6.0 × 10−7 M, respectively).

Novel aromatic substances, dictyomedin A and B, from Dictyostelium cellular slime molds and their inhibitory effects on Dictyostelium development

Abstract To elucidate the diversity of secondary metabolites of Dictyostelium cellular slime molds and search for physiologically active substances affecting their development, we investigated the constituents of D. medium. From the methanol extract of its fruit body, we obtained two novel aromatic compounds named dictyomedin A ( 1 ) and B ( 2 ), and their structures were elucidated by means of physicochemical data. Biological evaluation of the compounds showed that they delayed the differentiation of D. discoideum cells.

Virol A, a toxic trans-polyacetylenic alcohol of Cicuta virosa, selectively inhibits the GABA-induced Cl− current in acutely dissociated rat hippocampal CA1 neurons

The effects of virol A (VA), a toxic component of Cicuta virosa (water hemlock), on the GABA-induced Cl(-) current (I(GABA)) in acutely dissociated rat hippocampal CA1 neurons were investigated using whole-cell patch-clamp techniques. VA reversibly reduced I(GABA) and the muscimol (Mus)-induced current (I(Mus)) in a concentration-dependent manner. The IC(50) values for VA against I(GABA) and I(Mus) were 9.6x10(-7) and 9.8x10(-7) M, respectively. VA shifted the EC(50) value of I(GABA) from 6.5x10(-6) to 2.1x10(-5) M, whereas it had no effect on the maximum response, thereby suggesting that VA inhibited I(GABA) in a competitive manner. VA had no apparent effect on current-voltage relationships for I(GABA), thus indicating the lack of voltage-dependency. On the other hand, application of VA (10(-6) M) did not additionally reduce the I(GABA) suppressed by >10(-5) M picrotoxin. VA but not bicuculline accelerated the decay phase of I(GABA), as was seen with picrotoxin. Moreover, pre-application of 10(-5) M VA reduced I(GABA). VA did not inhibit that induced by glycine (10(-4) M). These results indicate that VA inhibits I(GABA) by acting both on the GABA agonist site and on the Cl(-) channel of the GABA(A) receptor-channel complex. VA is a structurally novel type of compound that selectively inhibits the GABA(A) receptor-Cl(-) channel complexes in mammalian central nervous system neurons.

Two lignan glycosides from Vitis thunbergii

Two new isolariciresinol-type lignan glycosides were isolated from Vitis thunbergii (Vitaceae) along with some oligostilbenes. Their structures were elucidated as (+)-3α-O-a-L-rhamnopyranosyl-5-methoxyisolariciresinol and(-)-3α-O-β-D-xylopyranosyl-6-O-β-D-glucopyranosylisolariciresinol, respectively, on the basis of the spectral evidence.

Three New Stilbeneoligomers from the Roots of Vitis vinifera "Kyohou"

Three new stilbeneoligomers named (+)-viniferol E, (+)-viniferether A and (+)-viniferether B were isolated from the roots of Vitis vinifera Kyohou and the structures were elucidated on the basis of the spectral evidence.

Alkylbenzoquinone Involved in Development of Cellular Slime Molds

The structure of the prespore-cell-promoting factor from Dictyostelium discoideum was determined to be 2-hydroxy-5-methyl-6-pentylbenzoquinone. The synthetic compound has prespore-cell-promoting activity similar to the natural one, with half-maximal induction at a concentration as low as 40 pM. It was also found that the factor induces aggregation in an aggregation-deficient mutant of a related species, Polysphodilium violaceum. Both these activities are sensitive to positional isomerism with the 6-methyl-5-pentyl isomer showing no detectable activity.