Structure of lampterol (illudin S)

The Luminous Fungi of Japan

Luminous fungi have long attracted public attention in Japan, from old folklore and fiction to current tourism, children's toys, games, and picture books. At present, 25 species of luminous fungi have been discovered in Japan, which correspond to approximately one-fourth of the globally recognized species. This species richness is arguably due to the abundant presence of mycophiles looking to find new mushroom species and a tradition of night-time activities, such as firefly watching, in Japan. Bioluminescence, a field of bioscience focused on luminous organisms, has long been studied by many Japanese researchers, including the biochemistry and chemistry of luminous fungi. A Japanese Nobel Prize winner, Osamu Shimomura (1928-2018), primarily focused on the bioluminescence system of luminous fungi in the latter part of his life, and total elucidation of the mechanism was finally accomplished by an international research team with representatives from Russia, Brazil, and Japan in 2018. In this review, we focused on multiple aspects related to luminous fungi of Japan, including myth, taxonomy, and modern sciences.

Non-peptide secondary metabolites from poisonous mushrooms: overview of chemistry, bioactivity, and biosynthesis

Covering: up to June 2021A wide variety of mushrooms have traditionally been recognized as edible fungi with high nutritional value and low calories, and abundantly produce structurally diverse and bioactive secondary metabolites. However, accidental ingestion of poisonous mushrooms can result in serious illnesses and even death. Chemically, mushroom poisoning is associated with secondary metabolites produced in poisonous mushrooms, causing specific toxicity. However, many poisonous mushrooms have not been fully investigated for their secondary metabolites, and the secondary metabolites of poisonous mushrooms have not been systematically summarized for details such as chemical composition and biosynthetic mechanisms. The isolation and identification of secondary metabolites from poisonous mushrooms have great research value since these compounds could be lethal toxins that contribute to the toxicity of mushrooms or could provide lead compounds with remarkable biological activities that can promote advances in other related disciplines, such as biochemistry and pharmacology. In this review, we summarize the structures and biological activities of secondary metabolites identified from poisonous mushrooms and provide an overview of the current information on these metabolites, focusing on their chemistry, bioactivity, and biosynthesis.

Omphaloprenol A: a new bioactive polyisoprenepolyol isolated from the mycelium of poisonous mushroom Omphalotus japonicus

Mushrooms of the Omphalotus genus are known to be rich in secondary metabolites. In the quest for new bioactive compounds, we analyzed the compounds isolated from the mycelium of the poisonous mushroom Omphalotus japonicus. As a result, a new polyisoprenepolyol, which was named omphaloprenol A, was identified, along with known substances such as hypsiziprenol A10 and A11, illudin S, and ergosterol. The chemical structure of omphaloprenol A was elucidated by nuclear magnetic resonance and infrared spectroscopies and mass spectrometry, and its bioactivity was investigated. Omphaloprenol A showed growth promoting activity against the root of lettuce seeds and cytotoxicity against HL60 cells. To the best of our knowledge, this is the first report on the isolation of a polyisoprenepolyol compound from Omphalotaceae mushrooms.

A Chemical Proteomic Analysis of Illudin-Interacting Proteins

The illudin natural product family are fungal secondary metabolites with a characteristic spirocyclopropyl-substituted fused 6,5-bicyclic ring system. They have been extensively studied for their cytotoxicity in various tumor cell types, and semisynthetic derivatives with improved therapeutic characteristics have progressed to clinical trials. Although it is believed that this potent alkylating compound class acts mainly through DNA modification, little is known about its binding to protein sites in a cellular context. To reveal putative protein targets of the illudin family in live cancer cells, we employed a semisynthetic strategy to access a series of illudin-based probes for activity-based protein profiling (ABPP). While the probes largely retained potent cytotoxicity, proteomic profiling studies unraveled multiple protein hits, suggesting that illudins exert their mode of action not from addressing a specific protein target but rather from DNA modification and unselective protein binding.

Application of High-speed Countercurrent Chromatography for the Purification of High-purity Illudin S from Omphalotus japonicus

Illudin S from mushroom, such as Omphalotus japonicus and illudens, is a natural sesquiterpene analog with strong anti-tumor and antiviral activities. These illudins compounds are highly effective against various drug-resistant cancers that show extreme cytotoxicity an in vitro assay. However, it is difficult to obtain a sufficient amount of highly pure illudin S from a natural product by simple, efficient and low-cost purification techniques. Here, we offer to apply the high-speed countercurrent chromatography for the preparative purification of illudin S from mushroom extract. For a two-solvent system, the optimal condition of hexane/ethyl acetate/methanol/water (1/5/1/5, v/v/v/v) was optimized to obtain pure illudin S from a crude extract. This purified component was evaluated by liquid chromatography (high-purity >99%) and tandem mass spectrometry. The yield amounts of illudin S (1.3 mg/about 10 g Omphalotus japonicus) at one running are determined by liquid chromatographic calibration. It is concluded that by requiring a natural material and cost-effectiveness, our method represents a significant improvement over complicated techniques for the purification of illudin S from natural materials.

Toxic isolectins from the mushroom Boletus venenatus

Ingestion of the toxic mushroom Boletus venenatus causes a severe gastrointestinal syndrome, such as nausea, repetitive vomiting, diarrhea, and stomachache. A family of isolectins (B. venenatus lectins, BVLs) was isolated as the toxic principles from the mushroom by successive 80% ammonium sulfate-precipitation, Super Q anion-exchange chromatography, and TSK-gel G3000SW gel filtration. Although BVLs showed a single band on SDS-PAGE, they were further divided into eight isolectins (BVL-1 to -8) by BioAssist Q anion-exchange chromatography. All the isolectins showed lectin activity and had very similar molecular weights as detected by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis. Among them, BVL-1 and -3 were further characterized with their complete amino acid sequences of 99 amino acids determined and found to be identical to each other. In the hemagglutination inhibition assay, both proteins failed to bind to any mono- or oligo-saccharides tested and showed the same sugar-binding specificity to glycoproteins. Among the glycoproteins examined, asialo-fetuin was the strongest inhibitor. The sugar-binding specificity of each isolectin was also analyzed by using frontal affinity chromatography and surface plasmon resonance analysis, indicating that they recognized N-linked sugar chains, especially Galbeta1-->4GlcNAcbeta1-->4Manbeta1-->4GlcNAcbeta1-->4GlcNAc (Type II) residues in N-linked sugar chains. BVLs ingestion resulted in fatal toxicity in mice upon intraperitoneal administration and caused diarrhea upon oral administration in rats.

Enantioselective total synthesis of (-)-acylfulvene and (-)-irofulven

We report our full account of the enantioselective total synthesis of (-)-acylfulvene (1) and (-)-irofulven (2), which features metathesis reactions for the rapid assembly of the molecular framework of these antitumor agents. We discuss (1) the application of an Evans Cu-catalyzed aldol addition reaction using a strained cyclopropyl ketenethioacetal, (2) an efficient enyne ring-closing metathesis cascade reaction in a challenging setting, (3) the reagent IPNBSH for a late-stage reductive allylic transposition reaction, and (4) the final RCM/dehydrogenation sequence for the formation of (-)-acylfulvene (1) and (-)-irofulven (2).

Ptaquiloside, the major toxin of bracken, and related terpene glycosides: chemistry, biology and ecology

Bracken (Pteridium spp.) is a ubiquitous fern which has been described as one of the five most common plants on the earth. The toxic effects of bracken on livestock have been recorded since the end of the 19th century, and extensive and intensive investigations for the bracken toxin(s) led to the isolation of ptaquiloside in 1983 as the major, but unstable, toxin of bracken. This review concentrates mainly on the results of the scientific investigations into ptaquiloside, and cites 133 references.

Total synthesis of the sesquiterpene (+/-)-illudin C via an intramolecular nitrile oxide cycloaddition

[reaction: see text] A convergent total synthesis of illudin C is described. The tricyclic ring system of the natural product was quickly assembled from cyclopropane and cyclopentene precursors via a novel oxime dianion coupling reaction and a subsequent intramolecular nitrile oxide-olefin cycloaddition.

Discovery and development of sesquiterpenoid derived hydroxymethylacylfulvene: a new anticancer drug

Hydroxymethylacylfulvene (HMAF, MGI 114) is derived from the sesquiterpene illudin S by treatment with dilute sulfuric acid and excess paraformaldehyde. It is less cytotoxic than illudin S but exhibits much greater selectivity in toxicity to malignant cells compared to normal cells. HMAF is believed to undergo bioreductive activation in vivo. It is now being tested in human clinical phase II trials against solid tumors.

Histopathological effects of illudin S, a toxic substance of poisonous mushroom, in rat

1. Rats were dosed orally with illudin S, a toxic substance derived from the poisonous mushroom Lampteromyces japonicus. The digestive tract showed severe damage, whereas the liver, kidney and lung did not show any significant changes. 2. The effects observed became more pronounced with increasing illudin S dose (5, 10 or 20 mg kg-1 body weight). 3. Severe inflammation and oedema were observed in the stomach and moderate changes in the proximal part of the small intestine. 4. Histopathological examination revealed haemorrhagic erosions and marked inflammatory oedema in the gastric mucosa.

Metabolism of illudin S, a toxic substance of Lampteromyces japonicus: urinary excretion of mercapturic acids in rat

1. The urinary excretion of the mercapturic acids of illudin S after oral administration to rat has been studied. 2. From lc-ms/ms analysis of methanolic extracts of lyophilized rat urine, stereo-isomeric mercapturic acids were detected. 3. The mercapturic acids excreted 3 days following administration amounted to approximately 0.39-0.73% of the administered dose. 4. In vitro glutathione conjugation of illudin S by subcellular fractions was also examined. 5. No significant increases in the formation of glutathione adducts were observed in any subcellular fractions examined.

Acylfulvenes, a new class of potent antitumor agents

Acylfulvene, derived from the sesquiterpene illudin S by treatment with acid (reverse Prins reaction), is far less reactive to thiols than illudin S. However, it is reduced readily to an aromatic product, in the same way as illudin S. This may explain its greatly improved therapeutic index compared to that of the parent compound.

Metabolism of illudin S, a toxic substance of Lampteromyces japonicus. IV. Urinary excretion of an illudin S metabolite in rat

1. The urinary excretion of a metabolite of illudin S after oral administration to rat has been studied. 2. From an ethyl acetate extract of urine, metabolite 1, a cyclopropane ring-cleavage compound, was identified by liquid chromatographic-mass spectrometric analysis 3. A hplc method for determination of the metabolite in rat urine was developed with extraction using Sep-Pak C18 cartridge followed by liquid-liquid extraction. 4. The metabolite excreted during 3 days after administration of illudin S to rat amounted to approximately 10-19% of the dose as free form and 3-5% of the dose as glucuronide.

Metabolism by rat liver cytosol of illudin S, a toxic substance of Lampteromyces japonicus. II. Characterization of illudin S-metabolizing enzyme

1. Enzyme systems responsible for formation of cyclopropane ring-cleavage metabolites (M1 and M2) of illudin S in rat liver were characterized. 2. The enzymes were localized in the cytosol fraction and utilized NADPH alone as electron donor; they were not affected by oxygen and had low pH optima. 3. Formation of metabolites M1 and M2 was inhibited completely by dicumarol (10(-4) M), an inhibitor of DT-diaphorase. 4. Menadione (10(-4) M) and quercetin (10(-4) M) both inhibited formation of M1 and M2 by 35% and 15%, respectively, but quinacrine, barbital, pyrazole and p-chloromercuribenzoic acid had no significant effect. 5. Results show that the enzyme systems may differ from DT-diaphorase, aldehyde oxidase, xanthine oxidase, ketone reductase, aldose reductase, aldehyde reductase and alcohol dehydrogenase, known cytosolic enzymes responsible for xenobiotic metabolism.

Metabolism of illudin S, a toxic principle of Lampteromyces japonicus, by rat liver. I. Isolation and identification of cyclopropane ring-cleavage metabolites

1. Illudin S, a toxic principle of the basidiomycete Lampteromyces japonicus, was incubated with rat liver 9000 g supernatant and its metabolites studied. 2. Two metabolites, M1 and M2, were isolated and identified as cyclopropane ring-cleavage compounds by n.m.r., i.r. and mass spectral analyses. Moreover, M2 contained a chlorine atom. 3. On the basis of detailed analyses of the 2D n.m.r. spectra and differential nuclear Overhauser effect experiments, the previous assignments of the cyclopropane carbons of illudin S were revised.

Mutagenicity of ptaquiloside, the carcinogen in bracken, and its related illudane-type sesquiterpenes. I. Mutagenicity in Salmonella typhimurium

Ptaquiloside, a potent carcinogen of an illudane-type sesquiterpene glycoside isolated from Pteridium aquilinum, and its related compounds, hypolosides having the same nucleus isolated from the Pteridaceae, exhibited marked mutagenicity in the modified Ames test with Salmonella typhimurium TA98 and TA100 using a preincubation at pH 8.5. Illudins M and S, sesquiterpenes of the same illudane type from basidiomycetes, also exhibited mutagenicity. The structural requirements for mutagenicity are discussed.

Lampteromyces bioluminescence--1. Identification of riboflavin as the light emitter in the mushroom L. japonicus

The bioluminescence of the luminous mushroom, Lampteromyces japonicus, was studied by using the mushroom gills and also the luminous mycelia, the latter being cultured from the isolated spores and grown in a potato sucrose medium. The luminescence intensity of the mushroom gills and the cultured mycelia was measured in an aqueous suspension under various conditions. The original intensity was enhanced by exposing the luminous cells to oxygen for several hours or to acids or bases for a short period. This enhancement enabled measurement of their bioluminescence spectra which were identical to the fluorescence spectrum of riboflavin, having a maximum at 524 nm. The green fluorescent substance was extracted with cold water from the mushroom and it was identified as riboflavin by spectroscopic and chromatographic analyses. Riboflavin was concluded to be the light emitter of this mushroom.

Mode of action illudin S

The effect of the antitumor antibiotic illudin S on bacterial macromolecular synthesis was investigated. Illudin S was found to be inhibitory to in vivo deoxyribonucleic acid (DNA) synthesis from thymidine. Ribonucleic acid (RNA) synthesis was inhibited only at a concentration of illudin S 10 times that which inhibited DNA synthesis. The rate of protein synthesis remained the same except for a brief initial inhibition. When thymidine triphosphate was used for in vitro DNA synthesis, inhibition by illudin S did not occur, as tested with partially purified DNA polymerase II from Escherichia coli pol A(1) (-), with E. coli DNA-dependent RNA polymerase, with E. coli pol A(1) (-) spheroplasts, and with frozen and thawed Bacillus subtilis cells. A protein fraction isolated from B. subtilis capable of forming thymidine mono-, di-, and triphosphates from thymidine was not inhibited by illudin S. Furthermore, (14)C-illudin S taken up by B. subtilis cells was reisolated unchanged, making an intracellular activation of illudin S unlikely. Therefore, an attractive hypothesis is that illudin S inhibits DNA synthesis from thymidine which does not proceed through deoxyribonucleoside triphosphates, the generally accepted substrates for DNA synthesis.