Protoilludane, Illudalane, and Botryane Sesquiterpenoids from the Endophytic Fungus Phomopsis sp. TJ507A

Asperustins A-J: Austocystins with Immunosuppressive and Cytotoxic Activities from Aspergillus ustus NRRL 5856

Ten new (1-10) and nine known (11-19) austocystins, along with four known anthraquinones (20-23), were isolated from the culture of Aspergillus ustus NRRL 5856 by bioactivity-guided fractionation. The structures of the new compounds were elucidated by spectroscopic data analysis, X-ray crystallographic study, the modified Mosher's method, [Rh2(OCOCF3)4]-induced ECD spectral analysis, and comparison of the experimental ECD spectra with those of the similar analogues. Compounds 1-8 represent the first examples of austocystins with a C-4' oxygenated substitution. The absolute configuration of 1″-hydroxy austocystin D (11) was determined by single-crystal X-ray diffraction and consideration of its biosynthetic origin. Compounds 5, 9, and 11 exhibited significant inhibitory effects against the proliferation of ConA-induced T cells with IC50 values of 1.1, 1.0, and 0.93 μM, respectively. Furthermore, these compounds suppressed the expression of IL-6 in a dose-dependent manner. Compounds 10-12 and 14 showed pronounced cytotoxicities against MCF-7 with IC50 values of 3.9, 1.3, 0.46, and 2.3 μM, respectively.

Gold-Catalyzed Cascade Cycloisomerization of 3-Allyloxy-1,6-diynes to Cyclopropyl- and Cyclobutyl-Fused Benzofurans and Chromen-3a(1H)-ols

A synthetic method for the efficient preparation of partially hydrogenated benzo[f]cyclobuta[cd]cyclopenta[h]benzofurans and cyclopropa[c]chromen-3a(1H)-ols that relies on the gold(I)-catalyzed cascade cycloisomerization of 3-allyloxy-1,6-diynes is described.

Nine undescribed oxidized ergosterols from the endophytic fungus Penicillium herquei and their cytotoxic activity

A chemical investigation of the EtOAc extract of the endophytic fungus Penicillium herquei led to the isolation of nine undescribed oxidized ergosterols, penicisterols A-I (1-9), along with ten known analogs (10-19). Their structures and absolute configurations were elucidated by a combination of spectroscopic data analysis, quantum-chemical electronic circular dichroism (ECD) calculations and comparisons, [Rh₂(OCOCF₃)₄]-induced ECD experiments, DFT-calculated ¹³C chemical shifts and DP4+ probability analysis. Compound 1 was a rare example of ergosterol in which the bond between C-8 and C-9 is cleaved to form an enol ether. Moreover, compound 2 possessed a rare (2,5-dioxo-4-imidazolidinyl)-carbamic acid ester group substituted at C-3. All undescribed oxidized ergosterols (1-9) were evaluated for their cytotoxic activity against five cancer cell lines including 4T1 (mouse breast carcinoma), A549 (human pulmonary carcinoma), HCT-116 (human colorectal carcinoma), HeLa (human cervical carcinoma) and Hepg2 (human hepatoma carcinoma) cells. Compounds 2 and 3 displayed moderate cytotoxic activity against 4T1, A549 and HeLa cells, with IC₅₀ values ranging from 17.22 to 31.35 μM.

Microorganism-Derived Molecules as Enzyme Inhibitors to Target Alzheimer's Diseases Pathways

Alzheimer's disease (AD) is the most common form of dementia. It increases the risk of other serious diseases and causes a huge impact on individuals, families, and socioeconomics. AD is a complex multifactorial disease, and current pharmacological therapies are largely based on the inhibition of enzymes involved in the pathogenesis of AD. Natural enzyme inhibitors are the potential sources for targeting AD treatment and are mainly collected from plants, marine organisms, or microorganisms. In particular, microbial sources have many advantages compared to other sources. While several reviews on AD have been reported, most of these previous reviews focused on presenting and discussing the general theory of AD or overviewing enzyme inhibitors from various sources, such as chemical synthesis, plants, and marine organisms, while only a few reviews regarding microbial sources of enzyme inhibitors against AD are available. Currently, multi-targeted drug investigation is a new trend for the potential treatment of AD. However, there is no review that has comprehensively discussed the various kinds of enzyme inhibitors from the microbial source. This review extensively addresses the above-mentioned aspect and simultaneously updates and provides a more comprehensive view of the enzyme targets involved in the pathogenesis of AD. The emerging trend of using in silico studies to discover drugs concerning AD inhibitors from microorganisms and perspectives for further experimental studies are also covered here.

Anti-Alzheimer's Natural Products Derived from Plant Endophytic Fungi

Alzheimer's is the most common cause of dementia worldwide and seriously affects patients' daily tasks. Plant endophytic fungi are known for providing novel and unique secondary metabolites with diverse activities. This review focuses primarily on the published research regarding anti-Alzheimer's natural products derived from endophytic fungi between 2002 and 2022. Following a thorough review of the literature, 468 compounds with anti-Alzheimer's-related activities are reviewed and classified based on their structural skeletons, primarily including alkaloids, peptides, polyketides, terpenoids, and sterides. The classification, occurrences, and bioactivities of these natural products from endophytic fungi are summarized in detail. Our results provide a reference on endophytic fungi natural products that may assist in the development of new anti-Alzheimer's compounds.

Ganoaustralins A and B, Unusual Aromatic Triterpenes from the Mushroom Ganoderma australe

Two triterpenes, ganoaustralins A (1) and B (2), featuring unprecedented 6/6/6/5/6 scaffolds were isolated from the fruiting bodies of the mushroom Ganoderma australe. The structures were determined by extensive NMR and HRESIMS spectroscopic analysis. The absolute configuration of the C-25 in ganoaustralin A was assigned by the phenylglycine methyl ester (PGME) method. The relative and absolute configurations of the polycyclic backbones were determined by NMR and ECD calculations, respectively. The plausible biosynthetic pathways of ganoaustralins A and B were proposed. Ganoaustralin B showed weak inhibition against β-secretase 1.

Five new secondary metabolites from an endophytic fungus Phomopsis sp. SZSJ-7B

Two previously undescribed lactones, phomolides A and B (1 and 2), and three new sesquiterpenoids, phomenes A-C (3-5), together with one known compound, colletotricholide A (6), were isolated from the endophytic fungus Phomopsis sp. SZSJ-7B. Their chemical structures, including the absolute configurations, were comprehensively established by extensive analyses of NMR, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism powered by theoretical calculations, and X-ray diffractions. Moreover, the cytotoxic and antibacterial activities of compounds 1-6 were also evaluated, and the results demonstrated that compound 2 showed significant antibacterial effects towards methicillin-resistant Staphylococcus aureus and S. aureus strains with minimum inhibitory concentration as low as 6.25 μg/ml, which was comparable to that of the clinical drug vancomycin. Moreover, all compounds showed no cytotoxic activity.

Epigenetic Manipulation Induced Production of Immunosuppressive Chromones and Cytochalasins from the Mangrove Endophytic Fungus Phomopsis asparagi DHS-48

A mangrove endophytic fungus Phomopsis asparagi DHS-48 was found to be particularly productive with regard to the accumulation of substantial new compounds in our previous study. In order to explore its potential to produce more unobserved secondary metabolites, epigenetic manipulation was used on this fungus to activate cryptic or silent genes by using the histone deacetylase (HDAC) inhibitor sodium butyrate and the DNA methyltransferase (DNMT) inhibitor 5-azacytidine (5-Aza). Based on colony growth, dry biomass, HPLC, and ¹H NMR analyses, the fungal chemical diversity profile was significantly changed compared with the control. Two new compounds, named phaseolorin J (1) and phomoparagin D (5), along with three known chromones (2–4) and six known cytochalasins (6–11), were isolated from the culture treated with sodium butyrate. Their structures, including their absolute configurations, were elucidated using a combination of detailed HRESIMS, NMR, and ECD and ¹³C NMR calculations. The immunosuppressive and cytotoxic activities of all isolated compounds were evaluated. Compounds 1 and 8 moderately inhibited the proliferation of ConA (concanavalin A)-induced T and LPS (lipopolysaccharide)-induced B murine spleen lymphocytes. Compound 5 exhibited significant in vitro cytotoxicity against the tested human cancer cell lines Hela and HepG2, which was comparative to the positive control adriamycin and fluorouracil. Our finding demonstrated that epigenetic manipulation should be an efficient strategy for the induction of new metabolites from mangrove endophytic fungi.

Immunosuppressive Cytochalasins from the Mangrove Endophytic Fungus Phomopsis asparagi DHS-48

Three new cytochalasins, phomoparagins A-C (1–3), along with five known analogs (4–8), were isolated from Phomopsis asparagi DHS-48, a mangrove-derived endophytic fungus. Their structures, including their absolute configurations, were elucidated using a combination of detailed HRESIMS, NMR, and ECD techniques. Notably, 1 possessed an unprecedented 5/6/5/8/5-fused pentacyclic skeleton. These compounds were tested for their inhibitory activity against concanavalin A (ConA)/lipopolysaccharide (LPS)-induced spleen lymphocyte proliferation and calcineurin (CN) enzyme. Several metabolites (2 and 4–6) exhibited fascinating inhibitory activities with a relatively low toxicity. Furthermore, 2 was demonstrated to inhibit ConA-stimulated activation of NFAT1 dephosphorylation and block NFAT1 translocation in vitro, subsequently inhibiting the transcription of interleukin-2 (IL-2). Our results provide evidence that 2 may, at least partially, suppress the activation of spleen lymphocytes via the CN/NFAT signaling pathway, highlighting that it could serve as an effective immunosuppressant that is noncytotoxic and natural.

Bioactive terpenoids derived from plant endophytic fungi: An updated review (2011-2020)

Plant endophytes have been considered as novel sources of naturally occurring compounds with various biological activities, including cytotoxic, antimicrobial, anti-inflammatory, anticancer, herbicides, antileishmanial and antioxidant. A variety of specialised products, comprising terpenoids, alkaloids, polyketides, phenolic compounds, coumarins, and quinone derivatives have been reported from various strains. An increasing number of products, especially terpenoids, are being isolated from endophytes. Herein, the isolated new terpenoids from plant endophytic fungi, their hosts, as well as biological activities, from January 2011 until the end of 2020 are reviewed. In this period, 516 terpenoids are classified into monoterpenes (5), sesquiterpenes (299), diterpenes (76), sesterterpens (22), meroterpenes (83), triterpenes (29), and other terpenoids (2), were isolated from different plant endophytic fungi species.

Isolation, absolute configurations and bioactivities of pestaphilones A-I: Undescribed methylated side chain containing-azaphilones from Pestalotiopsis oxyanthi

Nine undescribed side chain containing azaphilones, pestaphilones A-I, were isolated from the Anoectochilus roxburghii endophytic fungus Pestalotiopsis oxyanthi. The structures of these isolates were identified by spectroscopic data, electronic circular dichroism (ECD) calculations and comparisons, quantum-chemical ¹³C NMR calculations with DP4+ probability analysis, Rh₂(OCOCF₃)₄-induced ECD, acetonide formation, selective oxidation reaction and X-ray crystallographic data. Structurally, pestaphilones A-I were the first azaphilones characteristically formed via a methyl group at C-9 in the C₇ side chain. More importantly, a selective oxidation reaction was firstly set up to resolve the absolute configuration of flexible side chain containing azaphilones, and an acetonide formation based Rh₂(OCOCF₃)₄-induced ECD experiment was performed to identify the configurations of the oxygenated pyranoquinone core in the azaphilones. In bioassay, pestaphilones A-F displayed potential immunosuppressive activity in concanavalin A (Con A)-induced T lymphocyte proliferation, with IC₅₀ values ranging from (9.36 ± 1.14) μM to (35.21 ± 3.25) μM.

Endophytic Fungal Terpenoids: Natural Role and Bioactivities

Endophytic fungi are a highly diverse group of fungi that intermittently colonize all plants without causing symptoms of the disease. They sense and respond to physiological and environmental changes of their host plant and microbiome. The inter-organism interactions are largely driven by chemical networks mediated by specialized metabolites. The balance of these complex interactions leads to healthy and strong host plants. Endophytic strains have particular machinery to produce a plethora of secondary metabolites with a variety of bioactivities and unknown functions in an ecological niche. Terpenoids play a key role in endophytism and represent an important source of bioactive molecules for human health and agriculture. In this review, we describe the role of endophytic fungi in plant health, fungal terpenoids in multiple interactions, and bioactive fungal terpenoids recently reported from endophytes, mainly from plants used in traditional medicine, as well as from algae and mangroves. Additionally, we highlight endophytic fungi as producers of important chemotherapeutic terpenoids, initially discovered in plants. Despite advances in understanding endophytism, we still have much to learn in this field. The study of the role, the evolution of interactions of endophytic fungi and their terpenoids provide an opportunity for better applications in human health and agriculture.

Cytotoxic diaporindene and tenellone derivatives from the fungus Phomopsis lithocarpus

Nine new compounds, including five natural rarely-occurring 2, 3-dihydro-1H-indene derivatives named diaporindenes E-I (1-5), and four new benzophenone analogues named tenellones J-M (6-9) were isolated from the deep-sea sediment-derived fungus Phomopsis lithocarpus FS508. All the structures for these new compounds were fully characterized on the basis of spectroscopic data, NMR spectra, and ECD calculation and single-crystal X-ray diffraction analysis. The potential anti-tumor activities of compounds 1-9 against four tumor cell lines SF-268, MCF-7, HepG-2, and A549 were evaluated using the SRB method. Compound 7 exhibited cytotoxic activity against the SF-268 cell line with an IC₅₀ value of 11.36 μmol·L^-1.

Sesquiterpenoids Specially Produced by Fungi: Structures, Biological Activities, Chemical and Biosynthesis (2015-2020)

Fungi are widely distributed in the terrestrial environment, freshwater, and marine habitat. Only approximately 100,000 of these have been classified although there are about 5.1 million characteristic fungi all over the world. These eukaryotic microbes produce specialized metabolites and participate in a variety of ecological functions, such as quorum detection, chemical defense, allelopathy, and maintenance of symbiosis. Fungi therefore remain an important resource for the screening and discovery of biologically active natural products. Sesquiterpenoids are arguably the richest natural products from plants and micro-organisms. The rearrangement of the 15 high-ductility carbons gave rise to a large number of different skeletons. At the same time, abundant structural variations lead to a diversification of biological activity. This review examines the isolation, structural determination, bioactivities, and synthesis of sesquiterpenoids that were specially produced by fungi over the past five years (2015-2020).

Z, Cubilla-Rios L. Structurally Uncommon Secondary Metabolites Derived from Endophytic Fungi

Among microorganisms, endophytic fungi are the least studied, but they have attracted attention due to their high biological diversity and ability to produce novel and bioactive secondary metabolites to protect their host plant against biotic and abiotic stress. These compounds belong to different structural classes, such as alkaloids, peptides, terpenoids, polyketides, and steroids, which could present significant biological activities that are useful for pharmacological or medical applications. Recent reviews on endophytic fungi have mainly focused on the production of novel bioactive compounds. Here, we focus on compounds produced by endophytic fungi, reported with uncommon bioactive structures, establishing the neighbor net and diversity of endophytic fungi. The review includes compounds published from January 2015 to December 2020 that were catalogued as unprecedented, rare, uncommon, or possessing novel structural skeletons from more than 39 different genera, with Aspergillus and Penicillium being the most mentioned. They were reported as displaying cytotoxic, antitumor, antimicrobial, antiviral, or anti-inflammatory activity. The solid culture, using rice as a carbon source, was the most common medium utilized in the fermentation process when this type of compound was isolated.

Potential of Endophytic Diaporthe sp. as a New Source of Bioactive Compounds

Endophytic fungi are symbiotically related to plants and spend most of their life cycle within them. In nature, they have a crucial role in plant micro-ecosystem. They are harnessed for their bioactive compounds to counter human health problems and diseases. Endophytic Diaporthe sp. is a widely distributed fungal genus that has garnered much interest within the scientific community. A substantial number of secondary metabolites have been detected from Diaporthe sp. inhabited in various plants. As such, this minireview highlights the potential of Diaporthe sp. as a rich source of bioactive compounds by emphasizing on their diverse chemical entities and potent biological properties. The bioactive compounds produced are of significant importance to act as new lead compounds for drug discovery and development.

3-(Methoxycarbonyl)Cyclobutenone as a Reactive Dienophile in Enantioselective Diels-Alder Reactions Catalyzed by Chiral Oxazaborolidinium Ions

Cyclobutenone has been used as a highly reactive dienophile in Diels-Alder reactions, however, no enantioselective example has been reported. We disclose herein a chiral oxazaborolidine-aluminum bromide catalyzed enantioselective Diels-Alder reaction of 3-alkoxycarbonyl cyclobutenone with a variety of dienes. Furthermore, a total synthesis of (-)-kingianin F was completed for the first time via enantioenriched cycloadduct bicyclo[4.2.0]octane derivative.

Five new secondary metabolites from the fungus Phomopsis asparagi

Five new compounds, including a pair of diphenylcyclopentenone enantiomers (±)-phomopsisin A (1), a sesquiterpenoid 15-hydroxylithocarin A (2), a new diketopiperazine alkaloid prenylcyclotryprostatin A (3) and 7-hydroxy-cis-L(-)-3,6-dibenzyl-2,5-dioxopiperazine (6), along with five known compounds were isolated from the fungus Phomopsis asparagi. Their structures were elucidated on the basis of spectroscopic analyses (1D and 2D NMR), theoretical electronic circular dichroism (ECD) calculation, modified Mosher's method, and X-ray crystallography. The racemates of (±)-phomopsisin A showed inhibition on α-glucosidase with IC₅₀ of 30.07 ± 0.75 μM (positive control acarbose, 121 ± 2.7 μM).

Bioactive Secondary Metabolites of the Genus Diaporthe and Anamorph Phomopsis from Terrestrial and Marine Habitats and Endophytes: 2010-2019

The genus Diaporthe and its anamorph Phomopsis are distributed worldwide in many ecosystems. They are regarded as potential sources for producing diverse bioactive metabolites. Most species are attributed to plant pathogens, non-pathogenic endophytes, or saprobes in terrestrial host plants. They colonize in the early parasitic tissue of plants, provide a variety of nutrients in the cycle of parasitism and saprophytism, and participate in the basic metabolic process of plants. In the past ten years, many studies have been focused on the discovery of new species and biological secondary metabolites from this genus. In this review, we summarize a total of 335 bioactive secondary metabolites isolated from 26 known species and various unidentified species of Diaporthe and Phomopsis during 2010-2019. Overall, there are 106 bioactive compounds derived from Diaporthe and 246 from Phomopsis, while 17 compounds are found in both of them. They are classified into polyketides, terpenoids, steroids, macrolides, ten-membered lactones, alkaloids, flavonoids, and fatty acids. Polyketides constitute the main chemical population, accounting for 64%. Meanwhile, their bioactivities mainly involve cytotoxic, antifungal, antibacterial, antiviral, antioxidant, anti-inflammatory, anti-algae, phytotoxic, and enzyme inhibitory activities. Diaporthe and Phomopsis exhibit their potent talents in the discovery of small molecules for drug candidates.

Chiral lithium amide mediated desymmetrization of 3-substituted cyclobutanone

A practical approach to access enantioenriched cyclobutenes was developed via a chiral lithium amide mediated deprotonation of 3-substituted cyclobutanones. Further elaborations led to stereoselective assembly of tricyclic skeletons.

Divergent Michael/Aldol Cascades Under Semi-Aqueous Conditions: Synthesis of Cyclopenta- and Cycloheptannulated (Hetero)arenes

The synthesis of 3-acetoxyindanones and (hetero)arene-fused dihydrotropones was achieved via divergent annulation cascades. Under mild aqueous and basic conditions, α-substituted enone-aldehydes and 1,3-carbonyls undergo a Michael/aldol/hemiketalization/retro-aldol cascade for the formation of 3-acetoxyindanones possessing two contiguous stereogenic centers, one of which is an all-carbon quaternary center. On the other hand, the same enone-aldehydes generate new classes of fused-dihydrotropones upon reaction with 2,4-dioxobutanoates under merely the same reaction conditions via a Michael/aldol/lactonization/decarboxylation cascade.

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.

Bioactive sesquiterpene derivatives from mangrove endophytic fungus Phomopsis sp. SYSU-QYP-23: Structures and nitric oxide inhibitory activities

Eight new sesquiterpene derivatives (2, 4-6 and 10-13), along with five known analogues were isolated from the mangrove endophytic fungus Phomopsis sp. SYSU-QYP-23. Their structures of new compounds were established by spectroscopic methods, and the absolute configurations were confirmed by single-crystal X-ray diffraction analysis and comparison of the experimental ECD spectra. The absolute configuration of the side chain in 1 was first defined by modified Mosher's method. Compounds 1-7 showed potent inhibitory activities against nitric oxide (NO) production in lipopolysaccharides (LPS) induced RAW 264.7 cells with IC₅₀ values ranging from 8.6 to 14.5 μM. The molecular docking results implied that the bioactive sesquiterpenes may directly bind with targeting residues in the active cavity of iNOS protein.

Synthesis of Illudinine from Dimedone and Identification of Activity as a Monoamine Oxidase Inhibitor

The fungal metabolite illudinine is prepared in seven steps and ca. 55% overall yield from dimedone using an "open and shut" (ring-opening and ring-closing) strategy. Tandem ring-opening fragmentation and olefination of dimedone establishes alkyne and vinylarene functionality linked by a neopentylene tether. Oxidative cycloisomerization then provides the illudinine framework. The key innovation in this second-generation synthesis of illudinine is the use of the nitrile functional group, rather than an ester, as the functional precursor to the carboxylic acid of illudinine. The small, linear nitrile (C≡N) is associated with improved selectivity, π-conjugation, and reactivity at multiple points in the synthetic sequence relative to the carboxylic acid ester. Preliminary assays indicate that illudinine and several related synthetic analogues are monoamine oxidase inhibitors, which is the first reported indication of biological activity associated with this natural product. Illudinine was found to inhibit monoamine oxidase B (MAO-B) with an IC₅₀ of 18 ± 7.1 μM in preliminary assays.

Lithocaldehydes A and B, polyketones from the deep sea-derived fungus Phomopsis lithocarpus FS508

Lithocaldehydes A (1) and B (2), a pair of novel diastereoisomers possessing an unprecedented 6/6/5/5/6 highly-fused ring system forming an earring-like skeleton, were isolated from the deep sea-derived fungus Phomopsis lithocarpus FS508. The structures of 1 and 2 were fully characterized and established through extensive spectroscopic interpretations and ECD calculations. Moreover, compounds 1 and 2 were shown to be promising antibiotics, exhibiting potent antifungal activities that are comparable to those of the positive control nystatin.

Progress on Terpenoids With Biological Activities Produced by Plant Endophytic Fungi in China Between 2017 and 2019

Plant endophytic fungi are an important part of plant microecosystems and a natural resource for human survival and development. Various bioactive natural products produced by plant endophytic fungi show promising prospects in biopharmacy, agricultural production, and industrial fermentation. Terpenoids, the most numerous and structurally diverse natural products from endophytic fungi, possess a broad range of biological activities and huge potential for drug development. It is critically significant for ecological and economic benefits to develop their activities. This paper utilized literature analysis to summarize 200 terpenoids with biological activities that are derived from plant endophytic fungi in China between 2017 and 2019. Among them, sesquiterpenoids were the most important kind of terpenoids, and Trichoderma and Aspergillus species were main terpenoid-producing plant endophytic fungi. Furthermore, these terpenoids displayed multifarious biological activities, including antimicrobial, antipathogenic, and anti-inflammatory activities, as well as cytotoxicity, antitumor agents, and enzyme inhibition.

Biological Activity of Endophytic Fungi from the Roots of the Medicinal Plant Vernonia anthelmintica

Endophytic fungi were first isolated from the fresh root of the Chinese medicinal plant Vernonia anthelmintica collected from the Hotan Prefecture within the Xinjiang Autonomous region of the People’s Republic of China. This plant has been used in Uyghur traditional medicine to treat vitiligo, a skin condition characterized by patches of the skin losing their pigment. In total, fifteen fungal strains were isolated. Among these, four endophytic fungi were identified by their DNA sequences and registered to GenBank with accession numbers. The isolates were identified as Schizophyllum commune XJA1, Talaromyces sp. XJA4, Aspergillus sp. XJA6, Aspergillus terreus XJA8. Ethyl acetate extracts of all fungal strains were used to quantify melanin content and to identify in vitro biological activity assays including antimicrobial, antioxidant, cytotoxic, antidiabetic and tyrosinase activity on B16 cells. Among the extracts of all four identified strains, the ethyl acetate extract of the Aspergillus sp. XJA6 was chosen for further characterization because it presented the highest biological activity against these tests. In addition, twenty four volatile compounds from the petroleum ether fraction were characterized by GC–MS.

Chemical Diversity of β-Secretase Inhibitors From Natural Resources

Reports on β-secretase inhibitors of natural origin are listed in order to reveal their chemical diversity. Various types of compounds were found to inhibit β-secretase, and natural resources included a wide spectrum of biological species. Among them, some triterpenes and moracin derivatives, which are nonpeptidic compounds, were determined to be competitive inhibitors. In addition, no peptide compounds were reported from natural resources. These points will be clarified in future studies.

Two new cephalochromin derivative from the Alternaria sp. ZG22

Two new cephalochromin derivatives, prenylcephalochromin A (1), prenylcephalochromin B (2), along with cephalochromin (3) were isolated from the Alternaria sp. ZG22 obtained from a Dasymaschalon rostratum collected from the Hainan. The structures of two new compounds were elucidated by comprehensive spectroscopic methods. Compounds 1-3 showed α-glucosidase inhibitory activity.

Rhizophins A and B, new sesquiterpenes from the culture broth of Coprinus rhizophorus

Two new sesquiterpenes (1 and 2) together with one known compound (3) were isolated from the culture broth of Coprinus rhizophorus. Chemical structures of these compounds were deduced by spectroscopic methods. Compound 1 exhibited free-radical-scavenging activity against the 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical. Compounds 2 and 3 exhibited antimicrobial activities against Saccharomyces cerevisiae, Propionibacterium acnes, and Staphylococcus epidermidis.

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.

Total Syntheses of Allelopathic 4-Oxyprotoilludanes, Melleolides, and Echinocidins

Stereocontrolled total syntheses of allelopathic 4-oxyprotoilludane sesquiterpenes, melleolide, melleolide F, and echinocidins B and D were achieved. The curved 5/6/4 tricyclic system with an angular hydroxy group was built via three key transformations: (1) Me₃Al-catalyzed [2 + 2] cycloaddition of a ketene silyl acetal with a propiolate, (2) reductive ring-opening of a cyclic hemiketal, and (3) the intramolecular Morita-Baylis-Hillman reaction. This synthetic route represents a new and reliable strategy to obtain protoilludanes with several oxy-functional groups.

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.

Xanthone-derived polyketides from the Thai mangrove endophytic fungus Phomopsis sp. xy21

Six new xanthone-derived polyketides, named phomoxanthones F-K (1-6), along with three known ones, were isolated from Phomopsis sp. xy21, which was isolated as an endophytic fungus from the Thai mangrove Xylocarpus granatum. Phomoxanthone F (1) represents the first xanthone-derived polyketide containing a 10a-decarboxylated benzopyranone nucleus that was substituted by a 4-methyldihydrofuran-2(3H)-one moiety at C10a. Phomoxanthones G (2) and H (3) are highly oxidized xanthone-derived polyketides containing a novel 5-methyl-6-oxabicyclo[3.2.1]octane motif. This is the first report of a C6-O-C12 bridge in xanthone-derived polyketides. Additionally, a plausible biogenetic pathway for these xanthone-derived polyketides is proposed.

Polyketide and Prenylxanthone Derivatives from the Endophytic Fungus Aspergillus sp. TJ23

Eight secondary metabolites, including a new polyketide, named asperetide (1) and a new prenylxanthone derivative, called asperanthone (4), and six known compounds, (S)-3-butyl-7-methoxyphthalide (2), ruguloxanthone C (3), tajixanthone hydrate (5), tajixanthone methanoate (6), salimyxin B (7), and ergosterol (8), were isolated and identified from the medicinal plant-derived fungus, Aspergillus sp. TJ23. The new structures and their absolute configurations were elucidated via multiple methods, including 1D- and 2D-NMR, HR-ESI-MS, UV, IR, and the electronic circular dichroism (ECD) calculations. All of the isolates were characterized from the strain for the first time. The in vitro bioassay showed that compounds 3-5 and 8 exerted inhibitory activities against five cancer cell lines (B16, MDA-MB-231, 4T1, HepG2, and LLC) with IC₅₀ values ranging from 5.13 to 36.8 μm.

Highly Substituted Benzophenone Aldehydes and Eremophilane Derivatives from the Deep-Sea Derived Fungus Phomopsis lithocarpus FS508

Five new benzophenone derivatives named tenellones D–H (1–5), sharing a rare naturally occurring aldehyde functionality in this family, and a new eremophilane derivative named lithocarin A (7), together with two known compounds (6 and 8), were isolated from the deep marine sediment-derived fungus Phomopsis lithocarpus FS508. All of the structures for these new compounds were fully characterized and established on the basis of extensive spectroscopic interpretation and X-ray crystallographic analysis. Compound 5 exhibited cytotoxic activity against HepG-2 and A549 cell lines with IC₅₀ values of 16.0 and 17.6 μM, respectively.