Emi Okuyama

The structure of paraherquamide, a toxic metabolite from penicillium paraherquei

Abstract A new toxic metabolite was isolated from Penicillium paraherquei and the structure was determined by X-ray diffraction analysis. The metabolite was designated as paraherquamide.

Anthraquinone production by transformed root cultures of Rubia tinctorum: Influence of phytohormones and sucrose concentration

Hairy roots ofRubia tinctorum were induced by infection with Agrobacterium rhizogenes and cultured in Murashige and Skoog liquid medium containing 3% sucrose. The effects of the phytohormones IAA, NAA, 2,4-D and kinetin, and of sucrose concentration on the growth of the roots and anthraquinone production was studied. Roots cultured in liquid medium in the presence of 5,μM IAA showed the maximal growth rate and the highest anthraquinone production, while kinetin had no effect. Higher concentrations of sucrose (6–18%) inhibited growth in the presence of phytohormones (5,μM IAA or 0.5 μM NAA). In contrast, in phytohormone-free medium, 12% sucrose resulted in maximal growth and anthraquinone production.

Anisatin modulation of the γ-aminobutyric acid receptor-channel in rat dorsal root ganglion neurons

Anisatin, a toxic, insecticidally active component of Sikimi plant, is known to act on the GABA system. In order to elucidate the mechanism of anisatin interaction with the GABA system, whole‐cell and single‐channel patch clamp experiments were performed with rat dorsal root ganglion neurons in primary culture. Repeated co‐applications of GABA and anisatin suppressed GABA‐induced whole‐cell currents with an EC50 of 1.10 μM. No recovery of currents was observed after washout with anisatin‐free solution. However, pre‐application of anisatin through the bath had no effect on GABA‐induced currents. The decay phase of currents was accelerated by anisatin. These results indicate that anisatin suppression of GABA‐induced currents requires opening of the channels and is use‐dependent. Anisatin suppression of GABA‐induced currents was not voltage dependent. Picrotoxinin attenuated anisatin suppression of GABA‐induced currents. [3H]‐EBOB binding to rat brain membranes was competitively inhibited by anisatin. These data indicated that anisatin bound to the picrotoxinin site. At the single‐channel level, anisatin did not alter the open time but prolonged the closed time. The burst duration was reduced and channel openings per burst were decreased indicating that anisatin decreased the probability of openings.

Novel natural colorants from Monascus anka U-1

The structure of xanthomonasin A(C 21 H 24 O 7 ), a natural colorant with a novel carbon skeleton (furanoisophthalide), produced by a mutant strain of Monascus anka, has been determined by the application of INADEQUATE experiment as well as by the variety of correlation spectroscopic techniques

Paraherquonin, a new meroterpenoid from penicillium paraherquei

Abstract Paraherquonin, a new meroterpenoid was isolated from Penicillium paraherquei IFO 6234 and the structure was determined by X-ray diffraction analysis.

The molecular structure of 2α-hydroxyneoanisatin and structure-activity relationships among convulsant sesquiterpenes of the seco-prezizaane and picrotoxane types

The molecular structure of 2alpha-hydroxyneoanisatin, a positional isomer of the potent neurotoxin anisatin, was determined by X-ray crystallographic analysis. This compound and four further seco-prezizaane type sesquiterpene lactones previously isolated from Illicium floridanum, which represent different structural types with respect to the mode of cyclisation, did not induce anisatin/picrotoxinin-like convulsions in mice. Based on these results and literature data for other seco-prezizaanes, structural requirements for convulsant activity are discussed. Comparison of the three dimensional molecular shape and electrostatic properties of active and inactive seco-prezizaane type lactones with compounds of the picrotoxane type resulted in the identification of a common pharmacophore structure for these different skeletal classes of convulsant natural products.

Fumigatonin, a new meroterpenoid from Aspergillus fumigatus

Abstract The structure of fumigatonin, a new meroterpenoid isolated from Aspergillus fumigatus IFM 4482 was elucidated by X-ray analysis.

Casein kinase II inhibitors isolated from two Brazilian plants Hymenaea parvifolia and Wulffia baccata

Two dihydroflavonol rhamnosides (1 and 2) isolated from the bark of Hymenaea parvifolia and two pentacyclic triterpenoids (3 and 6) obtained from the leaves of Wulffia baccata have been found to exhibit inhibitory effects of casein kinase II (CK-II) dose-dependently, suggesting that at higher doses more than 10 microM, these four compounds may act as potent CK-II suppressors of the CK-II-mediated activation of 60S acidic ribosomal P proteins in vitro.

2-ethoxycarbonyl-1-hydroxyanthraquinone from Rubia akane

Abstract From the roots of Rubia akane, 1-hydroxy-2-methylanthraquinone and a new anthraquinone, 2-ethoxycarbonyl-1-hydroxyanthraquinone were isolated. The structure of the new compound was elucidated by spectroscopy and synthesis.

Bioactive Components of a Peruvian Herbal Medicine, Chucuhuasi (Maytenus amazonica)

With a view to the efficient and sustainable use of natural resources, we have studied the pharmacological effects and active components of traditional medicines to gain scientific understanding and develop rational use and also to obtain lead-molecules for conventional medicines.