Synthesis and biological activity of kalkitoxin and its analogues

Total syntheses of kalkitoxin, isolated from the Caribbean Lyngbya majuscula, and its analogues, 3-epi-, 7-epi-, 8-epi-, 10-epi-, 10-nor-, and 16-nor-kalkitoxin, were achieved via oxazolidinone-based diastereoselective 1,4-addition reaction of a methyl group and efficient TiCl(4)-mediated thiazoline ring formation as the key steps. The biological activities of synthetic kalkitoxin and its analogues were evaluated with brine shrimp.

Total synthesis of 10-isocyano-4-cadinene and its stereoisomers and evaluations of antifouling activities

The first enantioselective total synthesis of 10-isocyano-4-cadinene, a marine sesquiterpene isolated from nudibranchs of the family Phyllidiidae, and determination of its absolute stereochemistry were achieved. 10-Isocyano-4-cadinene is expected to be a novel nontoxic antifouling agent. In the synthesis, intermolecular Diels-Alder reaction and samarium diiodide induced Barbier-type cyclization were employed as key steps. The absolute configuration of 10-isocyano-4-cadinene was determined as (1S,6S,7R,10S) by comparison of the optical rotations between natural and synthetic samples. In addition, the authors successfully synthesized 10-epi- and di-1,6-epi-10-isocyano-4-cadinene through the same synthetic pathway. Antifouling activities against Balanus amphitrite with the cadinenes were also evaluated.

A stereoselective vanadium-dependent chloroperoxidase in bacterial antibiotic biosynthesis

Halogenases catalyze reactions that introduce halogen atoms into electron-rich organic molecules. Vanadium-dependent haloperoxidases are generally considered to be promiscuous halogenating enzymes that have thus far been derived exclusively from eukaryotes, where their cellular function is often disputed. We now report the first biochemical characterization of a bacterial vanadium-dependent chloroperoxidase, NapH1 from Streptomyces sp. CNQ-525, which catalyzes a highly stereoselective chlorination-cyclization reaction in napyradiomycin antibiotic biosynthesis. This finding biochemically links a vanadium chloroperoxidase to microbial natural product biosynthesis.

Asymmetric total synthesis of danicalipin A and evaluation of biological activity

Asymmetric total synthesis of danicalipin A was achieved. The synthesis was characterized by diastereoselective introduction of chlorine atoms. Biological activities with synthetic danicalipin A, its enantiomer, and racemate were also evaluated toward brine shrimp. Both enantiomers of danicalipin A showed almost the same activity.

Absolute configuration of chlorosulfolipids from the chrysophyta Ochromonas danica

We isolated eight chlorosulfolipids (1-8) from the chrysophyta Ochromonas danica (IAM CS-2), including five new chlorosulfolipids (2-5, 8). The planar structures of all the compounds were elucidated by 1D and 2D NMR and ESI-MS/MS analyses. We determined the relative configuration of seven chlorosulfolipids (1-7), including the most commonly known chlorosulfolipid, 2,2,11,13,15,16-hexachlorodocosane-1,14-disulfate (1), by J-based configuration analysis (JBCA). The absolute configuration of each compound was determined using a modified Mosher's method after chemical degradation. 2,2,11,13,15,16-Hexachloro-14-docosanol-1-sulfate (2) was the most toxic to brine shrimp (Artemia salina) larvae (LC(50) 0.27 microg/mL). Compounds 1 and 4-8 were less toxic (LC(50) 2.2-6.9 microg/mL). Compound 3 was not toxic at 30 microg/mL.

Modulation of carcinogen metabolizing enzymes by chromanone A; a new chromone derivative from algicolous marine fungus Penicillium sp

A marine fungal isolate, Penicillium sp. fungus isolated from seaweed, Ulva sp., led to the isolation of a new chromone derivatives, 2-(hydroxymethyl)-8-methoxy-3-methyl-4H-chromen-4-one (chromanone A). The structure was determined by interpretation of their spectroscopic data (1D and 2D NMR, MS, UV and IR). At the nitiation stage of carcinogenesis, carcinogens is activated by cytochrome P-450 1A (CYP1A) and detoxified by glutathione S-transferases (GST), quinine reductase (QR), and epoxide hydrolase (mEH). We tested the modulatory effect of chromanone A on these carcinogen metabolizing enzymes. The results indicated that chromanone A (4μg/ml) is a promising inhibitor of CYP1A activity up to 60% of the stimulated-CYP1A in murine hepatoma cells (Hepa1c1c7), and it significantly induced GST but not total thiols at low concentrations. Chromanone A had no influence on QR activity, while it resulted in a significant dose-dependant enhancement mEH activity in Hepa1c1c7 cells (P<0.05-0.01). Additionally, chromanone A possessed a potent specific radical scavenging activity against hydroxyl radicals more than peroxyl radicals that may be responsible for the inhibitory effect of chromanone A on the induced-DNA damage in cells. In conclusion, this study proved that chromanone A may act as an active tumor anti-initiating via modulation of carcinogen metabolizing enzymes and protection from DNA damage.

Micropeptins from the freshwater cyanobacterium Microcystis aeruginosa (NIES-100)

Micropeptins C (1), D (2), E (3), and F (4) have been isolated from the freshwater cyanobacterium Microcystis aeruginosa (NIES-100). The structures were elucidated by analyses of MS, NMR spectra, and chemical degradation. Micropeptins C, D, E, and F inhibited chymotrypsin with IC(50)'s of 1.1, 1.2, 1.0, and 1.5 microg/mL, respectively.

Aureobasidin, New Antifouling Metabolite from Marine-Derived Fungus Aureobasidium sp

Two antifouling compounds, aureobasidin (1), a new ester with an unusual 4,6-dihydroxydecanoic acid residue, and (3 R,5 S)-3,5-dihydroxydecanoic acid (2), were isolated from the marine-derived fungus Aureobasidium sp., in addition to (5 R,3 Z)-5-hydroxydec-3-enoic acid (3) and ( R)-3-hydroxydecanoic acid (4). The structures were unambiguously established by IR, 1D and 2D NMR spectroscopic and mass spectral data. Compounds 1-3 were found to be active against Bacillus subtilis, Escherichia coli and Staphyllococcus aureus. Compound 3 showed fungistatic activity against Candida albicans.

Aureobasidin, new antifouling metabolite from marine-derived fungus Aureobasidium sp

Two antifouling compounds, aureobasidin (1), a new ester with an unusual 4,6-dihydroxydecanoic acid residue, and (3R,5S)-3,5-dihydroxydecanoic acid (2), were isolated from the marine-derived fungus Aureobasidium sp., in addition to (5R,3Z)-5-hydroxydec-3-enoic acid (3) and (R)-3-hydroxydecanoic acid (4). The structures were unambiguously established by IR, 1D and 2D NMR spectroscopic and mass spectral data. Compounds 1-3 were found to be active against Bacillus subtilis, Escherichia coli and Staphyllococcus aureus. Compound 3 showed fungistatic activity against Candida albicans.

Antibacterial activity of halogenated sesquiterpenes from Malaysian Laurencia spp

During our studies on Malaysian Laurencia species, brominated metabolites, tiomanene, acetylmajapolene B, and acetylmajapolene A were isolated from an unrecorded species collected at Pulau Tioman, Pahang along with known majapolene B and majapolene A. Acetylmajapolene A was a mixture of diastereomers as in the case of majapolene A. Tiomanene may be a plausible precursor for acetylmajapolenes B and A. In addition, three known halogenated sesquiterpenes and two known halogenated C(15) acetogenins were found from other two unrecorded species collected at Pulau Karah, Terengganu and Pulau Nyireh, Terengganu, respectively. Some of these halogenated metabolites showed moderate antibacterial activity against some marine bacteria.

A ceramide and cerebroside from the starfish asterias amurensis Lütken and their plant-growth promotion activities

The new phytosphingosine-type ceramide asteriaceramide A (1) and glucocerebroside asteriacerebroside G (2), together with two known cerebrosides, asteriacerebrosides A and B, were isolated from lipophilic fractions of the whole bodies of the Northern Pacific starfish Asterias amurensis Lütken. The water-soluble fraction afforded two known asterosaponins, glycoside B(2) and asterosaponin-1. The structures of 1 and 2 were determined on the basis of chemical and spectroscopic evidence as (2S,3S,4R,13Z)-2-[(2'R)-2-hydroxyhexadecanoylamino]-13-docosene-1,3,4-triol (1) and 1-O-(beta-d-glucopyranosyl)-(2S,3R,4E,13Z)-2-[(2'R)-2-hydroxytetradecanoylamino]-4,13-docosadiene-1,3-diol (2). Compounds 1, 2, and asteriacerebrosides A and B promoted plant growth in sprouts of Brassica campestris.

Tichocarpols A and B, two novel phenylpropanoids with feeding-deterrent activity from the red alga Tichocarpus crinitus

Two novel phenylpropanoic acid derivatives, tichocarpol A (1) and tichocarpol B (2), were isolated along with floridoside and isethionic acid from the red alga Tichocarpus crinitus. The structures of these novel metabolites were elucidated using a combination of spectral (1D and 2D NMR techniques and ESIMS) and chemical methods. Compounds 1, 2, and floridoside exhibited feeding-deterrent activity against the sea urchin Strongylocentrotus intermedius.

Characterization of the preferred stereochemistry for the neuropharmacologic actions of antillatoxin

Antillatoxin is a potent ichthyotoxin and cytotoxin previously discovered from the marine cyanobacterium Lyngbya majuscula. Ensuing studies of its mechanism of action showed it to activate the mammalian voltage-gated sodium channel at a pharmacological site that is distinct from any previously described. The structure of antillatoxin, initially formulated from spectroscopic information, was subsequently corrected at one stereocenter (C-4) as a result of synthesis of four different antillatoxin stereoisomers (all possible C-4 and C-5 diastereomers). In the current study these four stereoisomers, (4R,5R)-, (4S,5R)-, (4S,5S)-, and (4R,5S)-antillatoxin, were characterized in five different biological assay systems: ichthyotoxicity to goldfish, microphysiometry using cerebellar granule cells (CGCs), lactose dehydrogenase efflux from CGCs, monitoring of intracellular Ca(2+) concentrations in CGCs, and cytotoxicity to Neuro 2a cells. Across these various biological measures there was great consistency in that the natural antillatoxin (the 4R,5R-isomer) was greater than 25-fold more potent than any of the other stereoisomers. Detailed NMR studies provided a number of torsion and distance constraints that were modeled using the MM2 force field to yield predicted solution structures of the four antillatoxin stereoisomers. The macrocycle and side chain of natural (4R,5R)-antillatoxin present an overall "L-shaped" topology with an accumulation of polar substituents on the external surface of the macrocycle and a hydrogen bond between N(H)-7' and the C(O)-1 carbonyl. The decreased potency of the three non-naturally occurring antillatoxin stereoisomers is certainly a result of their dramatically altered overall molecular topologies.

Enantioselective syntheses and biological studies of aeruginosin 298-A and its analogs: application of catalytic asymmetric phase-transfer reaction

Aeruginosin 298-A was isolated from the freshwater cyanobacterium Microcystis aeruginosa (NIES-298) and is an equipotent thrombin and trypsin inhibitor. A variety of analogs were synthesized to gain insight into the structure-activity relations. We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogs, in which all stereocenters were controlled by catalytic asymmetric phase-transfer reaction promoted by two-center asymmetric catalysts and catalytic asymmetric epoxidation promoted by a lanthanide-BINOL complex. Furthermore, serine protease inhibitory activities of aeruginosin 298-A and its analogs were examined.

Use of nitrogen stable isotope ratio of periphyton for monitoring nitrogen sources in a river system

In order to confirm the usefulness of the N stable isotope ratio of periphyton (mainly composed of attached algae) as an indicator for monitoring the N sources in river watersheds, we measured the isotope ratio of periphyton along the Chikuma River. In the river, both the concentrations of dissolved total nitrogen (DTN) and the delta15N values of periphyton increased downstream. Specific nitrogen loading rates (SNLR) calculated from administrative data also showed an increase downstream from 7 to 11 kg N ha(-1) yr(-1), with the increasing contribution by sewage and livestock waste from 6 to 40% to total N loading. There are significant positive relationships between the DTN concentration and the SNLR (r2=0.54, P<0.05), and the delta15N values of periphyton and the SNLR (r2=0.78, P<0.05). The increase in DTN concentration reflected the increase in input of N loading. The increase in delta15N of periphyton might reflect the increase in relative contribution by sewage and livestock waste down the river, especially the increase in sewage. The present study indicates the usefulness of the N stable isotope ratio of periphyton as an indicator for monitoring N sources in a river system.

Massaliatrema misgurni n. sp. (Trematoda: Heterophyidae) whose metacercariae encyst in loaches (Misgurnus anguillicaudatus)

Hitherto unknown metacercariae were found encysted in loaches (Misgurnus anguillicaudatus) from China. They were experimentally fed to golden hamsters, and gravid adults were recovered 1 week post-infection from their small intestines. A new species, Massaliatrema misgurni n. sp. (Heterophyidae), is described from the adults. This new species is different from M. gyrinicola Dollfus and Timon-David, 1960, in having a smaller acetabulum/oral sucker ratio, less branched vitellaria widely entering the intercecal anteroacetabular area and an almost median seminal receptacle; and from M. yamashitai Kamiya and Ohbayashi, 1975, in having a larger acetabulum/oral sucker ratio, with the seminal vesicle situated in the uterine loop and the vitellaria entering the intercecal anteroacetabular area. This report is the first record of M. anguillicaudatus as a second intermediate host of the genus Massaliatrema Dollfus and Timon-David, 1960.

Chiral phosphine-free Pd-mediated asymmetric allylation of prochiral enolate with a chiral phase-transfer catalyst

[reaction: see text]. A chiral phase-transfer catalyst has been applied to the asymmetric allylation of the tert-butyl glycinate-benzophenone Schiff base with various allylic acetates for the first time to give the allylated products in good yields and with comparable to higher enantioselectivity than for asymmetric alkylation at the same temperature (91-96% ee) without any chiral ligands for coordinating to the palladium.

Antillatoxin B, a neurotoxic lipopeptide from the marine cyanobacterium Lyngbya majuscula

Bioassay-guided fractionation of organic extracts from two Lyngbya majuscula collections led to the isolation of a new secondary metabolite, antillatoxin B, an unusual N-methyl homophenylalanine analogue of the potent neurotoxin antillatoxin. Its structure was deduced from 2D NMR and data comparisons with antillatoxin. Antillatoxin B exhibited significant sodium channel-activating (EC(50) = 1.77 microM) and ichthyotoxic (LC(50) = 1 microM) properties.

Antillatoxin is a marine cyanobacterial toxin that potently activates voltage-gated sodium channels

Antillatoxin (ATX) is a lipopeptide derived from the pantropical marine cyanobacterium Lyngbya majuscula. ATX is neurotoxic in primary cultures of rat cerebellar granule cells, and this neuronal death is prevented by either N-methyl-d-aspartate (NMDA) receptor antagonists or tetrodotoxin. To further explore the potential interaction of ATX with voltage-gated sodium channels, we assessed the influence of tetrodotoxin on ATX-induced Ca2+ influx in cerebellar granule cells. The rapid increase in intracellular Ca2+ produced by ATX (100 nM) was antagonized in a concentration-dependent manner by tetrodotoxin. Additional, more direct, evidence for an interaction with voltage-gated sodium channels was derived from the ATX-induced allosteric enhancement of [3H]batrachotoxin binding to neurotoxin site 2 of the alpha subunit of the sodium channel. ATX, moreover, produced a strong synergistic stimulation of [3H]batrachotoxin binding in combination with brevetoxin, which is a ligand for neurotoxin site 5 on the voltage-gated sodium channel. Positive allosteric interactions were not observed between ATX and either alpha-scorpion toxin or the pyrethroid deltamethrin. That ATX interaction with voltage-gated sodium channels produces a gain of function was demonstrated by the concentration-dependent and tetrodotoxin-sensitive stimulation of 22Na+ influx in cerebellar granule cells exposed to ATX. Together these results demonstrate that the lipopeptide ATX is an activator of voltage-gated sodium channels. The neurotoxic actions of ATX therefore resemble those of brevetoxins that produce neural insult through depolarization-evoked Na+ load, glutamate release, relief of Mg2+ block of NMDA receptors, and Ca2+ influx.

Sequential histopathological changes in vivo after suicide gene therapy of gastric cancer induced by N-methyl-N'-nitro-N-nitrosoguanidine in rats

Gastrointestinal cancer is the most important clinical target of gene therapy. Suicide gene therapy, such as with the herpes simplex virus type 1 thymidine kinase (HSV-TK) gene, has been shown to exert antitumor efficacy in various cancer models in vitro. We previously reported in situ gene transfer and gene therapy for gastric cancer induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) in dogs. Here, we describe the sequential histopathological changes after suicide gene therapy of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced gastric cancer in rats. Gastric tumors were induced by MNNG in 38 / 73 (52%) of Wistar strain rats. The suicide gene therapy group (14 rats) was subjected to in situ gene transfer with a recombinant adenovirus vector carrying the HSV-TK gene driven by CAG promoter (Ad.CAGHSV-TK) in gastric tumor, followed by the antiviral drug ganciclovir (GCV). To observe the histopathological changes at various times after HSV-TK / GCV gene therapy, groups of animals were sacrificed at 3, 8, and 30 days after gene transfer. Apoptosis in the gastric tumors was detected by the TUNEL method to assess the efficacy of HSV-TK / GCV gene therapy, and it was marked in the 8- and 30-day treatment groups compared to the sham operation controls (P < 0.001). Various histopathological changes, degeneration of cancer tissue and fibrosis after necrosis and apoptosis were significantly greater in the 30-day treatment group. The HSV-TK gene was detectable in peripheral blood by PCR until 30 days after gene transfer. These results may be useful in devising a method of suicide gene therapy for humans.

Asymmetric alkylation of tert-butyl glycinate Schiff base with chiral quaternary ammonium salt under micellar conditions

[reaction: see text] The asymmetric alkylation of the tert-butyl glycinate-benzophenone Schiff base 1 with various arylmethyl bromides catalyzed by O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (2) proceeded smoothly under micellar conditions (5 equiv of 1 M KOH and 0.4 equiv of Triton X-100) to give the alkylated products in good yields and with good enantioselectivity (72-85% ee), depending on the electrophiles.

Immunohistochemical analysis of distribution of RON receptor tyrosine kinase in human digestive organs

The immunohistochemical distribution of RON receptor tyrosine kinase in digestive organs of both human fetus and adult, including the esophagus, stomach, duodenum, small intestine, colon, rectum, liver, gallbladder, pancreas, and spleen, was investigated semiquantitively using an affinity-purified rabbit polyclonal antibody. RON was observed to be widely distributed throughout various digestive organs and cell types in humans. The immunoreactivity for RON was observed in the epithelium of the esophagus, small intestine, colon, hepatocytes, Kupffer cells, and splenic macrophages both in the adult and the fetus, suggesting that the MSP/RON signaling pathway possesses the proper biological properties to possibly be involved in morphogenesis or differentiation of cells in these organs and cell types. Several organs differed in immunoreactivity between adult and fetus. No immunoreactive cells were found in the pancreas of adults; however, immunoreactivity was observed in acinar cells and in some of the duct or ductular cells and endocrine cells of the islet of the fetus. Similarly, immunoreactivity was not observed in gastric mucosa except in the intestinal metaplastic cells in adults; however, immunoreactivity was found in the foveolar epithelium of the stomach of the fetus. Although the biological significance of RON in malignancy is unclear, the presence of RON immunoreactivity in the fetus and it lack in the adult may indicate that RON is a oncofetal substance in human pancreas and stomach.

[Gastric cancer--novel strategy of gene therapy for gastric cancer]

Recently stage-oriented treatment for gastric cancer has been done in Japan. Endoscopic mucosal resection for intramucosal cancer and wedge resection under laparoscopy for minimal invasive cancer in the stomach have been performed. For advanced gastric cancer, extended lymph node dissection(D2) has been applied as standard treatment in Japan. However, new strategy has been required for advanced gastric cancer with distant lymph node metastasis and/or peritoneal dissemination. It is well known that gene therapy for cancer has limitation of efficacy, but we believe the new strategy will be available in post-genome era for gastric cancer treatment using 1. developing novel adenovirus, 2. usage of drug delivery system and 3. effective treatment for adverse effect.