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Phytophthora are plant pathogens that damage agricultural products. Lycosides (1a–d), found in vegetable juice, have the potential to curb the rapid outbreak and crop damage caused by the asexual reproduction of Phytophthora. Here, aglycones 2a, b with slightly higher activity than lycosides were synthesized as a diastereomeric mixture (mix-2) possessing activity (IC50 = 4.1 µm) comparable with that of lycosides. The importance of the cyclohexanone structure and side-chain length was demonstrated via structure–activity relationship analysis using synthetic intermediates. In addition, the action mechanism of lycosides was investigated using transcriptome analysis, which revealed a contribution to proline biosynthesis inhibition, a process crucial for the asexual reproduction of Phytophthora. These findings indicate that lycosides (and aglycone) are environmentally benign agents that can be used for protecting agricultural products from Phytophthora pathogens.

Equol (7-hydroxy-3-(4′-hydroxyphenyl)-chroman, EQ), one of the major intestinally derived metabolites of daidzein, the principal isoflavane found in soybeans and most soy foods, has recently attracted increased interest as a health-beneficial compound for estrogen-dependent diseases. However, based on its structure with two p-substituted phenols, this study aimed to examine whether EQ is a substrate for tyrosinase and whether it produces o-quinone metabolites that are highly cytotoxic to melanocyte. First, the tyrosinase-catalyzed oxidation of EQ was performed, which yielded three EQ-quinones. They were identified after being reduced to their corresponding catechols with NaBH4 or L-ascorbic acid. The binding of the EQ-quinones to N-acetyl-L-cysteine (NAC), glutathione (GSH), and bovine serum albumin via their cysteine residues was then examined. NAC and GSH afforded two mono-adducts and one di-adduct, which were identified by NMR and MS analysis. It was also found that EQ was oxidized to EQ-di-quinone in cells expressing human tyrosinase. Finally, it was confirmed that the EQ-oligomer, the EQ oxidation product, exerted potent pro-oxidant activity by oxidizing GSH to the oxidized GSSG and concomitantly producing H2O2. These results suggest that EQ-quinones could be cytotoxic to melanocytes due to their binding to cellular proteins.

The heterothallic group of the plant pathogen Phytophthora can sexually reproduce between the cross-compatible mating types A1 and A2. The mating hormone α2, produced by A2 mating type and utilized to promote the sexual reproduction of the partner A1 type, is known to be biosynthesized from phytol. In this study, we identified 2 biosynthetic intermediates, 11- and 16-hydroxyphytols (1 and 2), for α2 by administering the synthetic intermediates to an A2-type strain to produce α2 and by administering phytol to A2 strains to detect the intermediates in the mycelia. The results suggest that α2 is biosynthesized by possibly 2 cytochrome P450 oxygenases via 2 hydroxyphytol intermediates (1 and 2) in A2 hyphae and secreted outside.

Neurogenerative diseases, such as Parkinson’s disease, are associated, not only with the selective loss of dopamine (DA), but also with the accumulation of reactive catechol-aldehyde, 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is formed as the immediate oxidation product of cytoplasmic DA by monoamine oxidase. DOPAL is well known to exhibit toxic effects on neuronal cells. Both catecholic and aldehyde groups seem to be associated with the neurotoxicity of DOPAL. However, the exact cause of toxicity caused by this compound remains unknown. Since the reactivity of DOPAL could be attributed to its immediate oxidation product, DOPAL-quinone, we examined the potential reactions of this toxic metabolite. The oxidation of DOPAL by mushroom tyrosinase at pH 5.3 produced conventional DOPAL-quinone, but oxidation at pH 7.4 produced the tautomeric quinone-methide, which gave rise to 3,4-dihydroxyphenylglycolaldehyde and 3,4-dihydroxybenzaldehyde as products through a series of reactions. When the oxidation reaction was performed in the presence of ascorbic acid, two additional products were detected, which were tentatively identified as the cyclized products, 5,6-dihydroxybenzofuran and 3,5,6-trihydroxybenzofuran. Physiological concentrations of Cu(II) ions could also cause the oxidation of DOPAL to DOPAL-quinone. DOPAL-quinone exhibited reactivity towards the cysteine residues of serum albumin. DOPAL-oligomer, the oxidation product of DOPAL, exhibited pro-oxidant activity oxidizing GSH to GSSG and producing hydrogen peroxide. These results indicate that DOPAL-quinone generates several toxic compounds that could augment the neurotoxicity of DOPAL.

Neuromelanin (NM) is a dark brown pigment found in dopaminergic neurons of the substantia nigra (SN) and in norepinephrinergic neurons of the locus coeruleus (LC). Although NM is thought to be involved in the etiology of Parkinson&rsquo, s disease (PD) because its content decreases in neurodegenerative diseases such as PD, details are still unknown. In this study, we characterized the biosynthetic pathway of the oxidation of dopamine (DA) by tyrosinase in the presence of thiol peptides and proteins using spectroscopic and high-performance liquid chromatography (HPLC) methods and we assessed the binding of DA via cysteine residues in proteins by oxidation catalyzed by redox-active metal ions. To examine whether the protein-bound DA conjugates exhibit pro-oxidant activities, we measured the depletion of glutathione (GSH) with the concomitant production of hydrogen peroxide. The results suggest that the fate of protein-bound DA conjugates depends on the structural features of the proteins and that DA-protein conjugates produced in the brain possess pro-oxidant activities, which may cause neurodegeneration due to the generation of reactive oxygen species (ROS) and the depletion of antioxidants.

The crop destroyer Phytophthora uses mating hormones α1 and α2 to commence its sexual reproduction. The α1-induced sexual reproduction of the A2 mating type was unexpectedly found to be interfered with by the counterhormone α2 that the A2 type itself produces to induce the sexual reproduction of the A1 type. A plausible mechanism is proposed based on structure–activity relationships.

Mature Nicotiana benthamiana shows stable resistance to the oomycete pathogen Phytophthora infestans. Induction of phytoalexin (capsidiol) production is essential for the resistance, which is upregulated via a mitogen-activated protein kinase (MAPK) cascade (NbMEK2-WIPK/SIPK) followed by ethylene signaling. In this study, NbNup75 (encodes a nuclear pore protein Nucleoporin75) was identified as an essential gene for resistance of N. benthamiana to P. infestans. In NbNup75-silenced plants, initial events of elicitor-induced responses such as phosphorylation of MAPK and expression of defense-related genes were not affected, whereas induction of later defense responses such as capsidiol production and cell death induction was suppressed or delayed. Ethylene production induced by either INF1 or NbMEK2 was reduced in NbNup75-silenced plants, whereas the expression of NbEAS (a gene for capsidiol biosynthesis) induced by ethylene was not affected, indicating that Nup75 is required for the induction of ethylene production but not for ethylene signaling. Given that nuclear accumulation of polyA RNA was increased in NbNup75-silenced plants, efficient export of mRNA from nuclei via nuclear pores would be important for the timely upregulation of defense responses. Collectively, Nup75 is involved in the induction of a later stage of defense responses, including the ethylene-mediated production of phytoalexin for the resistance of N. benthamiana to P. infestans.

The exposure of human skin to 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone, RK) is known to cause chemical/occupational leukoderma. RK has a structure closely related to 4-(4-hydroxyphenyl)-2-butanol (rhododendrol), a skin whitening agent that was found to cause leukoderma in the skin of consumers in 2013. Rhododendrol is a good substrate for tyrosinase and causes a tyrosinase-dependent cytotoxicity to melanocytes, cells that are responsible for skin pigmentation. Therefore, it is expected that RK exerts its cytotoxicity to melanocytes through the tyrosinase-catalyzed oxidation to cytotoxic o-quinones. The results of this study demonstrate that the oxidation of RK by mushroom tyrosinase rapidly produces 4-(3-oxobutyl)-1,2-benzoquinone (RK-quinone), which is converted within 10-20 min to (E)-4-(3-oxo-1-butenyl)-1,2-benzoquinone (DBL-quinone). These quinones were identified as their corresponding catechols after reduction by ascorbic acid. RK-quinone and DBL-quinone quantitatively bind to the small thiol N-acetyl-l-cysteine to form thiol adducts and can also bind to the thiol protein bovine serum albumin through its cysteinyl residue. DBL-quinone is more reactive than RK-quinone, as judged by their half-lives (6.2 min vs 10.5 min, respectively), and decays rapidly to form an oligomeric pigment (RK-oligomer). The RK-oligomer can oxidize GSH to GSSG with a concomitant production of hydrogen peroxide, indicating its pro-oxidant activity, similar to that of the RD-oligomer. These results suggest that RK is cytotoxic to melanocytes through the binding of RK-derived quinones to thiol proteins and the pro-oxidant activity of the RK-oligomer.

A library of extracts established from hundreds of marine organisms was screened by a cytotoxicity test. The active organic extract of an Okinawan marine sponge of the genus Dysidea was subjected to bioassay-guided fractionation to give three new polyoxygenated steroids dysideasterols F-H (1-3), together with two known related compounds (4 and 5). Their structures were confirmed by NMR and mass spectroscopic analyses. A characteristic structural feature of 2, 4 and 5 is an allylic epoxide, whereas this epoxide undergoes ring-opening by a neighbouring hydroxyl group to give a tetrahydrofuran ring in 1 and 3. All compounds 1-5 exhibited a similar cytotoxic effect with IC50 values of 0.15-0.3 µM against human epidermoid carcinoma A431 cells, demonstrating that the allylic epoxide moiety was not responsible for this cytotoxic effect.

We have previously demonstrated that coffee and caffeine ameliorated hyperglycemia in spontaneously diabetic KK-A(y) mice. This present study evaluates the antidiabetic effects of coffee and caffeine on high-fat-diet-induced impaired glucose tolerance in C57BL/6J mice. C57BL/6J mice fed a high-fat diet were given regular drinking water (control group), or a 2.5-fold-diluted coffee or caffeine solution (200 mg/L) for 17 weeks. The ingestion of coffee or caffeine improved glucose tolerance, insulin sensitivity, and hyperinsulinemia when compared with mice in the control group. The adipose tissue mRNA levels of inflammatory adipocytokines (MCP-1 and IL-6) and the liver mRNA levels of genes related to fatty acid synthesis were lower in the coffee and caffeine groups than those in the control group. These results suggest that coffee and caffeine exerted an ameliorative effect on high-fat-diet-induced impaired glucose tolerance by improving insulin sensitivity. This effect might be attributable in part to the reduction of inflammatory adipocytokine expression.

A bacterial artificial chromosome (BAC) library was constructed to isolate the biosynthetic gene cluster for the polyketide/peptide hybrid-type antibiotic cystothiazole A from the myxobacterium Cystobacter fuscus strain AJ-13278. Sequence analysis of a 63.9 kb contiguous region that encompasses the biosynthetic gene cluster (cta) led to the identification of a polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) hybrid gene cluster 32.1 kb in size, which consists of six open reading frames (ORFs), ctaB to ctaG, as well as downstream genes ctaJ and ctaK (1.0 and 0.9 kb, respectively) responsible for the final biosynthetic steps. The genes ctaB, ctaE, and ctaF encode PKSs, the genes ctaC and ctaG encode NRPSs, and ctaD encodes an NRPS-PKS hybrid enzyme. Disruption of ctaD impaired cystothiazole A production. Additionally, two downstream genes, ctaJ and ctaK, which encode a nitrilase and an O-methyltransferase, respectively, must be responsible for the final methyl ester formation in the cystothiazole A biosynthesis.

Three new steroid glycosides, linckosides C-E, were isolated from the Okinawan starfish Linckia laevigata. Their structures and partial stereochemistry were elucidated by spectroscopic methods and chemical derivatization. These metabolites are additional members of the linckosides that were previously discovered as a novel class of neuritogenic compounds. Each of them possesses two monosaccharide units at C-3 of a polyhydroxylated steroidal aglycon and at the side chain (C-28 or C-29). Linckosides C and D are the first steroids that possess a hydroxyisopropyl substituent at C-24 of the side chain. These compounds are not only potent inducers of neurite outgrowth on PC12 cells but also significant enhancers of nerve growth factor (NGF) to induce the neurite outgrowth. The structure-activity relationships within the linckosides revealed that the presence of xylopyranose at the side chain was important rather than arabinofuranose, but that the diversity of the side chain carbon skeleton was not.

Palladium-catalyzed cyclization-methoxycarbonylation of (2 R ,3 S )-3-methylpent-4-yne-1,2-diol ( 6 ) derived from (2 R ,3 S )-epoxybutanoate 5 followed by methylation gave the tetrahydro-2-furylidene acetate (−)- 7 , which was converted to the left-half aldehyde (+)- 3 . A Wittig reaction between (+)- 3 and the phosphoranylide derived from the bithiazole-type phosphonium iodide 4 using lithium bis(trimethylsilyl)amide afforded the (+)-cystothiazole G ( 2 ), whose spectral data were identical with those of the natural product (+)- 2 . Thus, the stereochemistry of cystothiazole G ( 2 ) was proved to be (4 R ,5 S ,6( E )).

This is the first identification of a long-chain fatty acyl-CoA synthetase in Drosophila by enzymatic characterization. The gene product of CG6178 (CG6178) in Drosophila melanogaster genome, which has a high sequence similarity to firefly luciferase, has been expressed and characterized. CG6178 showed long-chain fatty acyl-CoA synthetic activity in the presence of ATP, CoA and Mg2+, suggesting a fatty acyl adenylate is an intermediate. Recently, it was revealed that firefly luciferase has two catalytic functions, monooxygenase (luciferase) and AMP-mediated CoA ligase (fatty acyl-CoA synthetase). However, unlike firefly luciferase, CG6178 did not show luminescence activity in the presence of firefly luciferin, ATP, CoA and Mg2+. The enzymatic properties of CG6178 including substrate specificity, pH dependency and optimal temperature were close to those of firefly luciferase and rat fatty acyl-CoA synthetase. Further, phylogenic analyses strongly suggest that the firefly luciferase gene may have evolved from a fatty acyl-CoA synthetase gene as a common ancestral gene.

The enantiocontrolled total syntheses of all the stereoisomers of a myxobacterial antibiotic, cystothiazole A, are described. The natural syn stereochemistry at the C4–C5 position was controlled by the asymmetric Evans aldol process, whereas the anti relationship was introduced by a modified Evans aldol methodology. Starting with a known aldehyde, the common substrate of the aldol reactions, cystothiazole A and its three stereoisomers were synthesized in 9 steps. All three stereoisomers did not show antifungal activity even at a dosage 2500-fold that of cystothiazole A.

A novel polyhydroxy metabolite named Zooxanthellamide A, C 128 H 222 N 2 O 54 S 2 , was isolated from a cultured marine dinoflagellate, Symbiodinium sp., and the chemical structure was determined by spectroscopic methods.

Haliangicin is a beta-methoxyacrylate-type polyene antibiotic isolated from the unique marine myxobacterium Haliangium ochraceum. A further investigation of the extract of this microorganism has resulted in the isolation of haliangicin as well as its geometrical isomers. The configuration of the epoxide in haliangicin, which was unknown previously, was determined in this study. The planar structures with partial stereochemistry of these isomers were elucidated by spectroscopic analyses. The major isomer, cis-haliangicin, is a cis isomer of the epoxide portion of haliangicin. Haliangicins B approximately D are geometrical isomers of the polyene moiety, and present as an inseparable mixture of cis and trans epoxide isomers. Their antifungal activities were also evaluated in comparison with haliangicin.

Known polyene amide, clathrynamide A, and three novel related metabolites, debromoclathrynamide A, (4E,6E)-debromoclathrynamide A and (6E)-clathrynamide A, were isolated from an Okinawan marine sponge, Psammoclemma sp. The absolute stereochemistry of clathrynamide A was determined to be 3R,12R by the modified Mosher method. The structures of the three new compounds were elucidated by spectroscopic analyses as debromo derivatives and geometrical isomers. Their antifungal activities were also evaluated with a phytopathogenic fungus, indicating that both the bromine atom and double-bond geometry affected the activity.

The novel cerebroside, termitomycesphin I (1), and two known cerebrosides (2 and 3) were isolated from the edible mushroom, Termitomyces titanicus. The structures of 1-3 were determined and identified by interpreting the spectroscopic data.

Plants recognize certain microbial compounds as elicitors in their active defence mechanisms. It has been shown that a series of defence reactions are induced in potato plant cells after treatment with water-soluble hyphal wall components prepared from Phytophthora infestans. In this study, a methanol extract from mycelia of P. infestans (MEM), which contains lipophilic compounds, was used as another elicitor for the induction of the defence reactions in potato. MEM elicitor induced reactive oxygen species (ROS), especially O2(-) and H2O2 production, and nitric oxide (NO) generation in potato leaves and suspension-cultured cells. Hypersensitive cell death was detected in potato leaves within 6-8 h after MEM elicitor treatment. The accumulation of phytoalexins was detected by MEM elicitor treatment in potato tubers. In potato suspension-cultured cells, several defence-related genes were induced by MEM elicitors, namely Strboh, Sthsr203J, StPVS3, StPR1, and StNR5, which regulate various defence-related functions. Enhanced resistance against P. infestans was found in MEM-treated potato plants. These results suggested that MEM elicitor is recognized by host and enhances defence activities to produce substances inhibitory to pathogens.

Toxisch, aber dennoch esbar ist Adlerfarn, dessen Carcinogenitat seit langem ein Problem ist. Diese Ubersicht beschreibt die Isolierung, Struktur und Reaktivitat von Ptaquilosid 1, einem Adlerfarn-Carcinogen. Bei der Abspaltung von Glucose aus 1 entsteht das eigentliche Carcinogen, das die Adenin- und Guanin-Molekule der DNA alkyliert und sogar die DNA spaltet.

Mature Nicotiana benthamiana shows strong resistance to the potato late blight pathogen Phytophthora infestans. By screening using virus-induced random gene silencing, we isolated a gene for plant-specific calreticulin NbCRT3a as a required gene for resistance of N. benthamiana against P. infestans. NbCRT3a encodes an endoplasmic reticulum quality-control (ERQC) chaperone for the maturation of glycoproteins, including glycosylated cell-surface receptors. NbCRT3a-silenced plants showed no detectable growth defects but resistance to P. infestans was significantly compromised. Defense responses induced by the treatment with INF1 (a secretory protein of P. infestans), such as production of reactive oxygen species and accumulation of phytoalexins, were suppressed in NbCRT3a-silenced N. benthamiana. Expression of an ethylene-regulated gene for phytoalexin biosynthesis, NbEAS, was reduced in NbCRT3a-silenced plants, whereas the expression of salicylic acid–regulated NbPR-1a was not affected. Consistently, induction of ethylene production by INF1 was suppressed in NbCRT3a-silenced plants. Resistance reactions induced by a hyphal wall components elicitor prepared from P. infestans were also impaired in NbCRT3a-silenced plants. However, cell death induced by active mitogen-activated protein kinase kinase (NbMEK2DD) was not affected by the silencing of NbCRT3a. Thus, NbCRT3a is required for the initiation of resistance reactions of N. benthamiana in response to elicitor molecules derived from P. infestans.

Three new acylated spermidines and two known related compounds were isolated from the Okinawan soft coral, Sinularia sp. These compounds were N',N",N"-trimethylspermidines that are acylated by a methyl-branched unsaturated fatty acid. These acylspermidines showed potent cytotoxicity against human tumor cell lines at an IC(50) value of 17 ng/ml and the induction of apoptotic phenomena.

A new steroidal saponin was isolated from Ophiopogon japonicus. This saponin possesses a modification by 2-hydroxy-3-methylvalerylation of the hydroxyl group at C-4' of the sugar, linked to C-1 of the aglycone. It exhibited significant neuritogenic activity for PC12 cells. The structure-activity relationship revealed the aglycone, rather than the sugar moieties and acylation, to be important for the neuritogenic activity.

Natural products provide a rich source of biological tools, but elucidating their molecular targets remains challenging. Here we report a cell morphological profiling of a natural product library, which permitted the identification of bisebromoamide and miuraenamide A as actin filament stabilizers. Automated high-content image analysis showed that these two structurally distinct marine natural products induce morphological changes in HeLa cells similar to those induced by known actin-stabilizing compounds. Bisebromoamide and miuraenamide A stabilized actin filaments in vitro, and fluorescein-conjugated bisebromoamide localized specifically to actin filaments in cells. Cell morphological profiling was also used to identify actin-stabilizing or -destabilizing natural products from marine sponge extracts, leading to the isolation of pectenotoxin-2 and lyngbyabellin C. Overall, the results demonstrate that high-content imaging of nuclei and cell shapes offers a sensitive and convenient method for detecting and isolating molecules that target actin.

A new bromoallene metabolite, named aplysiallene, was isolated from the Japanese sea hare, Aplysia kurodai, as an Na, K-ATPase inhibitor. Its structure was elucidated by spectroscopic methods. The known metabolites, laurinterol and debromolaurinterol, isolated from this animal were also evaluated for their Na, K-ATPase inhibitory activity.

Dolastatin E ( 1 ), a new cyclic hexapeptide containing three kinds of five-membered heterocycles (oxazole, thiazole, and thiazolone), has been isolated from the Japanese sea hare Dolabella auricularia and its gross structure elucidated by spectroscopic analysis.

The absolute stereochemistry of dolastatin E ( 1 ), a cyclic hexapeptide isolated from the sea hare Dolabella auricularia , has been determined by a combination of the degradation experiments and total synthesis.

A new 22-membered macrolides, dolabelide A ( 1 ), and its deacetyl derivative, dolabelide B ( 2 ), have been isolated as cytotoxins from the Japanese sea hare Dolabella auricularia . The gross structures of 1 and 2 were determined by spectroscopic analysis, and their absolute stereochemistry was elucidated by a combination of chemical means and the NMR spectroscopic method.

A bioassay-directed fractionation of the cytotoxic constituents of the Japanese sea hare Dolabella auricularia resulted in the isolation of two 35-membered depsipeptides dolastatin G (1) and nordolastatin G (2), which showed cytotoxicity against HeLa S(3) cells with IC(50) values of 1.0 and 5.3 mg/mL, respectively. The gross structures of these substances were established by spectroscopic analysis including 2D NMR techniques. The absolute stereostructure of 1 was determined by chiral HPLC analysis of amino acid components obtained from acid hydrolysis of 1 and by the enantioselective syntheses of two degradation products arising from polyketide portions. Nordolastatin G (2) is a congener that has the same absolute stereochemistry as that of 1.

The enantioselective total synthesis of aplyronine A (1), a potent antitumor substance of marine origin, was achieved by a convergent approach. Three segments 4, 5, and 6, corresponding to the C5−C11, C21−C27, and C28−C34 portions of aplyronine A (1), were prepared using the Evans aldol reaction and the Sharpless epoxidation as key steps. The coupling reaction of 4 with iodide 7 followed by Julia olefination with sulfone 8 gave the C5−C20 segment 9, while the Julia coupling reaction between segments 5 and 6 provided the C21−C34 segment 10. Julia olefination between segments 9 and 10 and the subsequent four-carbon homologation reaction led to seco acid 83, which was converted into aplyronine A (1) by Yamaguchi lactonization followed by the introduction of two amino acids. The use of the [(3,4-dimethoxybenzyl)oxy]methyl group as a protecting group for the hydroxyl at C29 was crucial for this synthesis. The enantioselective synthesis of two natural congeners, aplyronines B (2) and C (3), was also carried out...

Two ceramide 1-sulfates 1 and 2 have been isolated from the Japanese Bryozoa Watersipora cucullata as new potent inhibitors of a human DNA topoisomerase I. The gross structures of 1 and 2 were determined by spectroscopic analysis, and their absolute stereochemistry was elucidated by the optical data of degradation products.

Several C 27 –C 30 unsaturated fatty acids have been isolated from an Australian sponge, Amphimedon sp., as human DNA topoisomerase I inhibitors. Three of them, amphimic acids A ( 1 )-C ( 3 ), are unusual fatty acids possessing a cyclopropylidene group, and one is a new C 30 fatty acid 4 . Their structures were elucidated by spectroscopic analysis and chemical degradation. The enantioselective synthesis of 1 was carried out to determine the absolute configuration of amphimic acids. The inhibitory activity of DNA topoisomerase I was evaluated for these natural products and synthetic derivatives.

The structures of topostins, a novel type of mammalian DNA topoisomerase I inhibitors isolated from the bacterium Flexibacter topostinus sp. nov., have remained unknown. Reexamination of the production of topostins resulted in the isolation of original topostins B (B553 (1) and B567 (2)) and new related compounds named topostins D (D640 (3) and D654 (4)). Their structures, including the absolute stereochemistry, were determined by spectroscopic analyses and chemical degradations. These substances are lipid-containing amino acids and peptides.

Bithiazole-type antifungal products, cystothiazoles C-F (3–6), have been isolated from a culture broth of the myxobacterium Cystobacter fuscus as minor components. These are structurally related to cystothiazole A (1), which was isolated as a cytotoxic antibiotic from the same microorganism in our previous work. The structures of these compounds were elucidated by spectroscopic analyses. These new compounds inhibit the phytopathogenic fungus, Phytophthora capsici, but are less active than 1.

A novel dimeric polybrominated benzofuran, iantheran A ( 1 ), was isolated from an Australian marine sponge, lanthella sp., as a Na,K-ATPase inhibitor. The unique structure of 1 was determined on the basis of chemical and spectroscopic evidence.

Chromatographic fractionation, monitored by brine shrimp bioassay, led to the isolation of the first protoilludane-type sesquiterpene glucoside, pteridanoside (5), from a bioactive hot-water extract of the neotropical bracken fern Pteridium aquilinum var. caudatum (Dennstaedtiaceae). The enzymatic hydrolysis of 5 yielded its aglycon, pteridanone (6), and D-glucose. The absolute stereostructure of 5 was confirmed by the CD spectroscopic analysis of 6. Pteridanoside (5) exhibited toxicity (LC50 of 250 μg/ml at 24 h and 62.5 μg/ml at 48 h) toward brine shrimp, while the aglycon 6 did not.

Two new steroid glycosides, named linckosides A and B, were isolated from the Okinawan starfish Linckia laevigata, and their stereostructures were elucidated by spectroscopic methods and chemical derivatization. Each of them possesses two monosaccharide units at C-3 and C-29 of a polyhydroxylated steroid aglycon. These steroid glycosides showed not only notable neuritogenic activity against PC12 cells but also significant synergistic effects on the NGF-induced neuronal differentiation of PC12 cells. Linckoside B showed higher activities than those of linckoside A, though the structural difference is only the kind of a sugar.

From the sea hares belonging to two genera, Aplysia and Dolabella, a variety of new cytotoxic substances were isolated as minute constituents: their chemical structures were determined and their cytotoxicity was evaluated. Regarding the highly cytotoxic substances, further chemical and biological studies were performed that included their asymmetric chemical synthesis and elucidation of biological characteristics such as antitumor activity.