Five new bioactive sesquiterpenes from the fungus Radulomyces confluens (Fr.) Christ

A Review of Fungal Protoilludane Sesquiterpenoid Natural Products

Natural products have been a great source for drug leads, due to a vast majority possessing unique chemical structures. Such an example is the protoilludane class of natural products which contain an annulated 5/6/4-ring system and are almost exclusively produced by fungi. They have been reported to possess a diverse range of bioactivities, including antimicrobial, antifungal and cytotoxic properties. In this review, we discuss the isolation, structure elucidation and any reported bioactivities of this compound class, including establishment of stereochemistry and any total syntheses of these natural products. A total of 180 protoilludane natural products, isolated in the last 70 years, from fungi, plant and marine sources are covered, highlighting their structural diversity and potential in drug discovery.

Marine Terpenoids from Polar Latitudes and Their Potential Applications in Biotechnology

Polar marine biota have adapted to thrive under one of the ocean’s most inhospitable scenarios, where extremes of temperature, light photoperiod and ice disturbance, along with ecological interactions, have selected species with a unique suite of secondary metabolites. Organisms of Arctic and Antarctic oceans are prolific sources of natural products, exhibiting wide structural diversity and remarkable bioactivities for human applications. Chemical skeletons belonging to terpene families are the most commonly found compounds, whereas cytotoxic antimicrobial properties, the capacity to prevent infections, are the most widely reported activities from these environments. This review firstly summarizes the regulations on access and benefit sharing requirements for research in polar environments. Then it provides an overview of the natural product arsenal from Antarctic and Arctic marine organisms that displays promising uses for fighting human disease. Microbes, such as bacteria and fungi, and macroorganisms, such as sponges, macroalgae, ascidians, corals, bryozoans, echinoderms and mollusks, are the main focus of this review. The biological origin, the structure of terpenes and terpenoids, derivatives and their biotechnological potential are described. This survey aims to highlight the chemical diversity of marine polar life and the versatility of this group of biomolecules, in an effort to encourage further research in drug discovery.

Synthesis of Four Illudalane Sesquiterpenes Utilizing a One-Pot Diels-Alder/Oxidative Aromatization Sequence

The concise, divergent total syntheses of four illudalane sesquiterpenes using an indanone as the key intermediate are reported. The key elements in these total syntheses, which involve only four to six operational steps, consist of a Suzuki cross-coupling and a one-pot Diels-Alder/oxidative aromatization reaction.

Divergent total syntheses of five illudalane sesquiterpenes and assignment of the absolute configuration

Concise, divergent total syntheses of five bioactive illudalane sesquiterpenes have been achieved. Our synthesis features an intermolecular [2+2+2] cycloaddition, and a lactone-directed aromatic C-H oxygenation to generate a temporary phenolic hydroxyl group which enables regioselective methylation. Furthermore, the absolute configuration of radulactone was assigned by chemical synthesis.

The impact of Andean Patagonian mycoflora in the search for new lead molecules

Secondary metabolites from fungi have become a major source of chemical innovation in programs searching for lead molecules with bioactivities, especially over the last 50 years. In this review, we discuss the fundamental considerations in the discovery of molecules for agricultural and medicinal uses. This group of organisms possesses a strong potential for scientific and industrial communities. Recently, the incorporation of new technologies for the artificial cultivation of fungi and the use of better equipment to isolate and identify active metabolites has allowed the discovery of leading molecules for the design of new and safer drugs and pesticides. The geographical region including the Patagonian Andes mountains harbors a wide diversity of fungi, many of them still unknown and so far associated with Chilean-Argentinian Andean endemic forests. There have been very few chemical studies of the fungi located in this region. However, those few studies have allowed the discovery of new molecules. We argue that the richness of fungal biodiversity in this region offers an interesting source for the discovery of bioactive molecules for the basic and applied sciences.

Protoilludane, Illudane, Illudalane, and Norilludane Sesquiterpenoids from Granulobasidium vellereum

Two new and seven known sesquiterpene compounds were isolated from an agar plate culture of Granulobasidium vellereum, isolated from a log of Ulmus sp. The two new structures were elucidated with spectroscopic methods as an illudalane derivative, granulolactone (1), and a 15-norilludane, granulodione (9). The acaricidal and insecticidal activities of the isolated compounds were examined in vitro against two major horticultural pests, the two-spotted spider mite Tetranychus urticae and the glasshouse thrips Heliothrips haemorrhoidalis, respectively.

Chemoenzymatic Total Syntheses of the Enantiomers of the Protoilludanes 8-Deoxydihydrotsugicoline and Radudiol

Chemoenzymatic and stereoselective total syntheses of the non-natural enantiomeric forms of the recently isolated protoilludane natural products 8-deoxydihydrotsugicoline (1) and radudiol (2) (viz. ent-1 and ent-2, respectively) are reported. The key steps involve the Diels-Alder cycloaddition of cyclopent-2-en-1-one to the acetonide derived from enantiomerically pure and enzymatically derived cis-1,2-dihydrocatechol 3, elaboration of the resulting adduct to the tricyclic ketone 12, and a photochemically promoted rearrangement of this last compound to the octahydro-1H-cyclobuta[e]indenone 13.

Cytotoxic Illudane Sesquiterpenes from the Fungus Granulobasidium vellereum (Ellis and Cragin) Jülich

Eight illudane sesquiterpenes were obtained from the wood-decomposing fungus Granulobasidium vellereum (Ellis and Cragin) Jülich; among them were the enantiomers of the known compounds illudin M (1) and dihydroilludin M (4) and the diastereomers of illudin M (2) and illudin S (3), as well as two previously undescribed illudanes (5, 6). The cytotoxicity of compounds 1-4 and 6 was evaluated against two tumor cell lines (Huh7 and MT4), which showed that compounds 1-3 had potent cytotoxic activity, whereas compounds 4 and 6 had no or only moderate effects at concentrations up to 400 μM. Surprisingly, both compounds 2 and 3 were about 10 times more potent than 1. When the chemical reactivity of 1 and 2 was tested, compound 2 was shown to have a substantially higher reaction rate when reacted both with 2 M HCl and with cysteine, indicating that the difference in cytotoxicity is probably due to chemical reactivity and not to enzymatic affinity.

New environmentally-friendly antimicrobials and biocides from Andean and Mexican biodiversity

Persistent application of pesticides often leads to accumulation in the environment and to the development of resistance in various organisms. These chemicals frequently degrade slowly and have the potential to bio-accumulate across the food chain and in top predators. Cancer and neuronal damage at genomic and proteomic levels have been linked to exposure to pesticides in humans. These negative effects encourage search for new sources of biopesticides that are more "environmentally-friendly" to the environment and human health. Many plant or fungal compounds have significant biological activity associated with the presence of secondary metabolites. Plant biotechnology and new molecular methods offer ways to understand regulation and to improve production of secondary metabolites of interest. Naturally occurring crop protection chemicals offer new approaches for pest management by providing new sources of biologically active natural products with biodegradability, low mammalian toxicity and environmentally-friendly qualities. Latin America is one of the world's most biodiverse regions and provide a previously unsuspected reservoir of new and potentially useful molecules. Phytochemicals from a number of families of plants and fungi from the southern Andes and from Mexico have now been evaluated. Andean basidiomycetes are also a great source of scientifically new compounds that are interesting and potentially useful. Use of biopesticides is an important component of integrated pest management (IPM) and can improve the risks and benefits of production of many crops all over the world.

Cytotoxic illudalane sesquiterpenes from the wood-decay fungus Granulobasidium vellereum (Ellis & Cragin) Jülich

Seven illudalane sesquiterpenes were obtained from the wood decomposing fungus Granulobasidium vellereum: granuloinden A, granuloinden B and dihydrogranuloinden, along with the previously known compounds radulactone, pterosin M, echinolactone A and D. Granuloinden B showed potent cytotoxic activity against the Huh7 and MT4 tumor cell lines (CC₅₀ values of 6.7 and 0.15 µM, respectively), whereas granuloinden A and dihydrogranuloinden had no or moderate activity.

Sesquiterpenes from the saprotrophic fungus Granulobasidium vellereum (Ellis & Cragin) Jülich

Twelve sesquiterpenes comprising either the protoilludane or the rare cerapicane carbon skeletons were obtained from the saprotrophic wood decomposing fungus Granulobasidium vellereum; 2a-hydroxycoprinolone (1), 3-hydroxycoprinolone (2), coprinolone diol B (3), granulodiene A (4), granulodiene B (5), granulone A (6), 8-deoxy-4a-hydroxytsugicoline B (7), granulone B (8), demethylgranulone (9), cerapicolene (10), as well as the known compounds radudiol and Δ(6)-coprinolone. The structures were determined using spectroscopic methods and biosynthetic considerations. Granulone A had growth stimulating effect on the total elongation of lettuce seedlings. None of the isolated compounds showed any antifungal effect.

Protoilludane sesquiterpenes from the wood decomposing fungus Granulobasidium vellereum (Ellis & Cragin) Jülich

The secondary metabolites of the saprotrophic wood-decay basidiomycete fungus Granulobasidium vellereum were studied. Six sesquiterpenes were obtained; 2-hydroxycoprinolone (1), 8-deoxy-4a-hydroxytsugicoline (2), 8-deoxydihydrotsugicoline (3), which were previously not described, radulone A and B, and coprinolone ketodiol. Additionally, base-treatment of 1 yielded the diagnostic degradation products 1a and 1b, whereas radulone A was found to form 4 under mild acidic conditions. The structures were determined by NMR, MS, CD and polarimetry, along with biosynthetic considerations. Radulone A fully inhibited the spore germination of the potentially competing fungi Phlebiopsis gigantea, Coniophora puteana and Heterobasidion occidentale at 10μM, 500μM and 100μM, respectively. None of the other substances tested gave rise to any growth inhibition.

Illudalane sesquiterpenoids, echinolactones A and B, from a mycelial culture of Echinodontium japonicum

Illudalane sesquiterpenoids, echinolactones A and B, were isolated from the culture broth of the fungus Echinodontium japonicum, and their structures spectroscopically determined.

Illudalane sesquiterpenoids from the soft coral Alcyonium paessleri: the first natural nitrate esters

Fifteen illudalane sesquiterpenoids, alcyopterosins A-O (1-15) have been isolated from the subAntarctic soft coral Alcyonium paessleri which was collected at a depth of 200 m near the South Georgia Islands, and their structures were elucidated by spectroscopic techniques. Eight of these compounds (2, 3, 5-8, 10, and 13) are the first natural nitrate esters, while the other four (1, 4, 11, and 12) are chlorinated. These compounds are as well the first illudalane sesquiterpenoids to be isolated from the marine environment. Compounds 1, 3, 5, and 8 showed mild cytotoxicity toward human tumor cell lines.