Phenylspirodrimanes with anti-HIV activity from the sponge-derived fungus Stachybotrys chartarum MXH-X73

Phenylspirodrimane with Moderate Reversal Effect of Multidrug Resistance Isolated from the Deep-Sea Fungus Stachybotrys sp. 3A00409

Two new phenylspirodrimanes, stachybotrins K and L (1 and 2), together with eight known analogues (3-10), were isolated from deep-sea-derived Stachybotrys sp. MCCC 3A00409. Their structures were determined by extensive NMR data and mass spectroscopic analysis. Absolute configurations of new compounds were determined through a comparison of their circular dichroism (CD) spectra with other reported compounds. The possible reversal effects of all compounds were assayed in the resistant cancer cell lines. Stachybotrysin B (8) can reverse multidrug resistance (MDR) in ABCB1-overexpression cells (KBv200, Hela/VCR) at the non-cytotoxic concentration. Doxorubicin accumulation assay and molecular-docking analysis reveal that the mechanism of its reversal MDR effect may be related to the increase in the intracellular concentration of substrate anticancer drugs.

A new phenylspirodrimane derivative from the deep-sea-derived fungus Stachybotrys chartarum FS705

A new phenylspirodrimane derivative named stachybotrysin A (1), together with four known analogues (2-5) were isolated and purified from the solid culture of the deep-sea-derived Stachybotrys chartarum FS705. Their structures were determined by comprehensive spectroscopic analysis and the absolute configuration was evaluated by theoretical ECD calculations. Compounds 1-5 were evaluated for their cytotoxic, antibacterial and α-glucosidase inhibitory activities. The results showed that compound 2 displayed mild cytotoxicity with IC50 values in the range of 8.88 ∼ 22.73 µM against four human tumour cell lines, SF-268, MCF-7, HepG-2, and A549. Compound 1 showed strong α-glucosidase inhibitory activity with an IC50 value of 20.68 µM. Compounds 4 and 5 exhibited weak antibacterial activity against Bacillus subtilis.

Aureane-type sesquiterpene tetraketides as a novel class of immunomodulators with interleukin-17A inhibitory activity

Interleukin (IL)-17A, a pro-inflammatory cytokine, is a fundamental function in the onset and advancement of multiple immune diseases. To uncover the primary compounds with IL-17A inhibitory activity, a large-scale screening of the library of traditional Chinese medicine constituents and microbial secondary metabolites was conducted using splenic cells from IL-17A-GFP reporter mice cultured under Th17-priming conditions. Our results indicated that some aureane-type sesquiterpene tetraketides isolated from a wetland mud-derived fungus, Myrothecium gramineum, showed remarkable IL-17A inhibitory activity. Nine new aureane-type sesquiterpene tetraketides, myrogramins A-I (1, 4-11), and two known ones (2 and 3) were isolated and identified from the strain. Compounds 1, 3, 4, 10, and 11 exhibited significant IL-17A inhibitory activity. Among them, compound 3, with a high fermentation yield dose-dependently inhibited the generation of IL-17A and suppressed glycolysis in splenic cells under Th17-priming conditions. Strikingly, compound 3 suppressed immunopathology in both IL-17A-mediated animal models of experimental autoimmune encephalomyelitis and pulmonary hypertension. Our results revealed that aureane-type sesquiterpene tetraketides are a novel class of immunomodulators with IL-17A inhibitory activity, and hold great promise applications in treating IL-17A-mediated immune diseases.

Epigenetic Induction of Secondary Metabolites Production in Endophytic Fungi Penicillium chrysogenum and GC-MS Analysis of Crude Metabolites with Anti-HIV-1 Activity

The continuous burden of human immunodeficiency virus-1 in Sub-Saharan Africa, coupled with the inability of antiretroviral agents to eradicate HIV-1 from viral reservoirs, the potential risks of drug resistance development, and the development of adverse effects, emphasizes the need to develop a new class of HIV-1 inhibitors. Here, we cultivated four endophytic fungal isolates from a medicinal plant, Albizia adianthifolia with the addition of small epigenetic modifiers, sodium butyrate, and valproic acid, to induce the expression of biosynthetic gene clusters encoding active secondary metabolites with probable anti-HIV activities. We identified a non-toxic crude extract of the endophytic fungus Penicillium chrysogenum treated with sodium butyrate to possess significantly greater anti-HIV activity than the untreated extracts. Penicillium chrysogenum P03MB2 showed anti-HIV activity with an IC₅₀ of 0.6024 µg/mL compared to untreated fungal crude extract (IC₅₀ 5.053 µg/mL) when treated with sodium butyrate. The profile of secondary metabolite compounds from the bioactive, partially purified extracts were identified by gas chromatography-mass spectrometry (GC-MS), and more bioactive compounds were detected in treated P. chrysogenum P03MB2 fractions than in untreated fractions. Pyrrolo[1,2-a]pyrazine-1,4-dione, hexahydro (13.64%), cyclotrisiloxane, hexamethyl (8.18%), cyclotetrasiloxane, octamethyl (7.23%), cyclopentasiloxane, decamethyl (6.36%), quinoline, 1,2-dihydro-2,24-trimethyl (5.45%), propanenitrile (4.55%), deca-6,9-diene (4.55%), dibutyl phthalate (4.55%), and silane[1,1-dimethyl-2-propenyl)oxy]dimethyl (2.73%) were the most abundant compounds. These results indicate that treatment of endophytic fungi with small epigenetic modifiers enhances the secretion of secondary metabolites with stronger anti-HIV-1 properties, acknowledging the feasibility of epigenetic modification as an innovative approach for the discovery of cryptic fungal metabolites which can be developed into therapeutic compounds.

Developments in Exploring Fungal Secondary Metabolites as Antiviral Compounds and Advances in HIV-1 Inhibitor Screening Assays

The emergence of drug-resistant Human Immunodeficiency Virus-1 strains against anti-HIV therapies in the clinical pipeline, and the persistence of HIV in cellular reservoirs remains a significant concern. Therefore, there is a continuous need to discover and develop new, safer, and effective drugs targeting novel sites to combat HIV-1. The fungal species are gaining increasing attention as alternative sources of anti-HIV compounds or immunomodulators that can escape the current barriers to cure. Despite the potential of the fungal kingdom as a source for diverse chemistries that can yield novel HIV therapies, there are few comprehensive reports on the progress made thus far in the search for fungal species with the capacity to produce anti-HIV compounds. This review provides insights into the recent research developments on natural products produced by fungal species, particularly fungal endophytes exhibiting immunomodulatory or anti-HIV activities. In this study, we first explore currently existing therapies for various HIV-1 target sites. Then we assess the various activity assays developed for gauging antiviral activity production from microbial sources since they are crucial in the early screening phases for discovering novel anti-HIV compounds. Finally, we explore fungal secondary metabolites compounds that have been characterized at the structural level and demonstrate their potential as inhibitors of various HIV-1 target sites.

Natural sesquiterpene quinone/quinols: chemistry, biological activity, and synthesis

Covering: 2010 to 2021Sesquiterpene quinone/quinols (SQs) are characterized by a C15-sesquiterpenoid unit incorporating a C6-benzoquinone/quinol moiety. Numerous unprecedented carbon skeletons have been constructed with various connection patterns between the two parts. The potent anti-cancer, anti-inflammatory, anti-microbial, anti-viral, and fibrinolytic activities of SQs are associated with their diverse structures. The representative avarol has even entered the stage of clinical phase II research as an anti-HIV agent, and was developed as paramedic medicine against psoriasis. This review provides an overall summary of 558 new natural SQs discovered between 2010 and 2021, including seven groups and sixteen structure-type subgroups, which comprehensively recapitulates their chemical structures, spectral characteristics, source organisms, biological activities, synthesis, and biosynthesis, aiming to expand the application scope of this unique natural product resource.

New Phenylspirodrimanes from the Sponge-Associated Fungus Stachybotrys chartarum MUT 3308

Two phenylspirodrimanes, never isolated before, stachybotrin J (1) and new stachybocin G (epi-stachybocin A) (2), along with the already reported stachybotrin I (3), stachybotrin H (4), stachybotrylactam (5), stachybotrylactam acetate (6), 2α-acetoxystachybotrylactam acetate (7), stachybotramide (8), chartarlactam B (9), and F1839-J (10) were isolated from the sponge-associated fungus Stachybotrys chartarum MUT 3308. Their structures were established based on extensive spectrometric (HRMS) and spectroscopic (1D and 2D NMR) analyses. Absolute configurations of the stereogenic centers of stachybotrin J (1), stachybocin G (2), and stachybotrin I (3), were determined by comparison of their experimental circular dichroism (CD) spectra with their time-dependent density functional theory (TD-DFT) circular dichroism (ECD) spectra. The putative structures of seventeen additional phenylspirodrimanes were proposed by analysis of their respective MS/MS spectra through a Feature-Based Molecular Networking approach. All the isolated compounds were evaluated for their cytotoxicity against five aggressive cancer cell lines (MP41, 786, 786R, CAL33, and CAL33RR), notably including two resistant human cancer cell lines (786R, CAL33RR), and compounds 5, 6, and 7 exhibited cytotoxicity with IC50 values in the range of 0.3−2.2 µM.

Microbial Natural Products with Antiviral Activities, Including Anti-SARS-CoV-2: A Review

The SARS-CoV-2 virus, which caused the COVID-19 infection, was discovered two and a half years ago. It caused a global pandemic, resulting in millions of deaths and substantial damage to the worldwide economy. Currently, only a few vaccines and antiviral drugs are available to combat SARS-CoV-2. However, there has been an increase in virus-related research, including exploring new drugs and their repurposing. Since discovering penicillin, natural products, particularly those derived from microbes, have been viewed as an abundant source of lead compounds for drug discovery. These compounds treat bacterial, fungal, parasitic, and viral infections. This review incorporates evidence from the available research publications on isolated and identified natural products derived from microbes with anti-hepatitis, anti-herpes simplex, anti-HIV, anti-influenza, anti-respiratory syncytial virus, and anti-SARS-CoV-2 properties. About 131 compounds with in vitro antiviral activity and 1 compound with both in vitro and in vivo activity have been isolated from microorganisms, and the mechanism of action for some of these compounds has been described. Recent reports have shown that natural products produced by the microbes, such as aurasperone A, neochinulin A and B, and aspulvinone D, M, and R, have potent in vitro anti-SARS-CoV-2 activity, targeting the main protease (M^pro). In the near and distant future, these molecules could be used to develop antiviral drugs for treating infections and preventing the spread of disease.

Chemical Diversity and Biosynthesis of Drimane-Type Sesquiterpenes in the Fungal Kingdom

Drimane-type sesquiterpenes are a class of compounds produced by a wide range of organisms, initially isolated and characterized in plants. Meanwhile, in the past 20-30 years, a large number of novel structures from many divergent fungi have been elucidated. Recently, the biosynthesis of drimane-type sesquiter-penes and their esters has been explained in two filamentous fungi, namely Aspergillus oryzae and Aspergillus calidoustus, disclosing the basic biosynthetic principles needed to identify similar pathways in the fungal kingdom.

Stachybotrys chartarum-A Hidden Treasure: Secondary Metabolites, Bioactivities, and Biotechnological Relevance

Fungi are renowned as a fountainhead of bio-metabolites that could be employed for producing novel therapeutic agents, as well as enzymes with wide biotechnological and industrial applications. Stachybotrys chartarum (black mold) (Stachybotriaceae) is a toxigenic fungus that is commonly found in damp environments. This fungus has the capacity to produce various classes of bio-metabolites with unrivaled structural features, including cyclosporins, cochlioquinones, atranones, trichothecenes, dolabellanes, phenylspirodrimanes, xanthones, and isoindoline and chromene derivatives. Moreover, it is a source of various enzymes that could have variable biotechnological and industrial relevance. The current review highlights the formerly published data on S. chartarum, including its metabolites and their bioactivities, as well as industrial and biotechnological relevance dated from 1973 to the beginning of 2022. In this work, 215 metabolites have been listed and 138 references have been cited.

Brunneosporopsis yunnanensis gen. et sp. nov. and Allocryptovalsa xishuangbanica sp. nov., New Terrestrial Sordariomycetes from Southwest China

Three fungal taxa were collected on dead branches of wood during fieldwork in Sichuan and Yunnan Provinces, China. The new generic name Brunneosporopsis gen. nov. and species B. yunnanensis sp. nov. are introduced for a novel taxon characterized by globose to subglobose and dark olivacous-brown conidia. Phylogenetic analyses based on combined LSU, SSU and tef1-α loci strongly support the monophyly of this taxon and place it in the subclass Diaporthomycetidae. It could not be assigned to any currently recognized families in the subclass and was, therefore, placed in the Diaporthomycetidae genera incertae sedis. A second taxon represents a new species in Allocryptovalsa based on an analysis of the sequence datasets of ITS and btub loci of the novel, brown-spored sexual morphic species. This taxon is described here as A. xishuangbanica sp. nov. An interesting hypocrealean fungus producing synnemata, Stilbocrea gracilipes, was collected from dead wood of an unknown host from Sichuan Province and is reported here, with asexual morph from both the host and culture as well as LSU, ITS, tef1-α, rpb2 and rpb1 sequence data.

A Novel Approach for Fast Screening of a Complex Cyanobacterial Extract for Immunomodulatory Properties and Antibacterial Activity

The filamentous cyanobacteria from genus Phormidium are rich natural sources of bioactive compounds that could be exploited as pharmaceuticals or nutraceuticals. In this study, we suggest a novel approach for assessing the immunomodulatory properties of the products derived from cyanobacteria. The influence of Phormidium papyraceum extract on the human leukocyte immunophenotype was evaluated by attempting to link this activity to certain putative compounds identified in the extract. By using three staining panels and flow cytometry, we found that the cyanobacterial extract affected mainly CD4+ T cells upregulating activated CD4+CD152+ T cells (15.75 ± 1.93% treated vs. 4.65 ± 1.41% control) and regulatory CD4+CD25+ T cells (5.36 ± 0.64% treated vs. 1.03 ± 0.08% control). Furthermore, P. papyraceum extract can modulate T cell subpopulations with a CD4+ effector/memory phenotype. Extract-treated cells showed increased production of IL-2 (55 ± 12 pg/mL) and IL-6 (493 ± 64 pg/mL) compared to the untreated, 21 ± 7 pg/mL and 250 ± 39 pg/mL, respectively. No significant changes were observed in the secretion of TNF-α. In addition, P. papyraceum extract displayed antibacterial activity against both Gram-negative (inhibition zone from 18.25 ± 0.50 mm to 20.28 ± 1.50 mm) and Gram-positive (inhibition zone from 10.86 ± 0.85 mm to 17.00 ± 0.82 mm) bacteria. The chemical profile of the cyanobacterial extract was determined using LC–ESI–MS/MS analysis, where at least 112 putative compounds were detected. Many of these compounds have proven different biological activities. We speculated that compounds such as betulin and the macrolide azithromycin (or their analogues) could be responsible for the immunomodulatory potential of the investigated extract. More studies are needed to determine and validate the biological activities of the determined putative compounds.

Biosynthesis of Fungal Drimane-Type Sesquiterpene Esters

Drimane-type sesquiterpenes exhibit various biological activities and are widely present in eukaryotes. Here, we completely elucidated the biosynthetic pathway of the drimane-type sesquiterpene esters isolated from Aspergillus calidoustus and we discovered that it involves a drimenol cyclase having the same catalytic function previously only reported in plants. Moreover, since many fungal drimenol derivatives possess a γ-butyrolactone ring, we clarified the functions of the cluster-associated cytochrome P450 and FAD-binding oxidoreductase discovering that these two enzymes are solely responsible for the formation of those structures. Furthermore, swapping of the enoyl reductase domain in the identified polyketide synthase led to the production of metabolites containing various polyketide chains with different levels of saturation. These findings have deepened our understanding of how fungi synthesize drimane-type sesquiterpenes and the corresponding esters.

Recent advances in the discovery of novel marine natural products and mycosporine-like amino acid UV-absorbing compounds

Abstract

Bioactive compounds from marine environments represent a rich source of bioproducts for potential use in medicine and biotechnology. To discover and identify novel marine natural products (MNPs), evaluating diverse biological activities is critical. Increased sensitivity and specificity of omics technologies, especially next-generation high-throughput sequencing combined with liquid chromatography-mass spectrometry and nuclear magnetic resonance, are speeding up the discovery of novel bioactive compounds. Mycosporine-like amino acids (MAAs) isolated from many marine microorganisms are among highly promising MNPs characterized by ultraviolet radiation (UV) absorbing capacities and are recognized as a potential source of ecologically friendly sunscreens. MAAs absorb damaging UV radiation with maximum absorption in the range of 310–360 nm, including both UVA and UVB ranges. MAAs are also characterized by other biological activities such as anti-oxidant, anti-cancer, and anti-inflammatory activities. The application of modern omics approaches promoted some recent developments in our understanding of MAAs’ functional significance and diversity. This review will summarize the various modern tools that could be applied during the identification and characterization of MNPs, including MAAs, to further their innovative applications.

Key points

• New omics technologies are speeding up the discovery of novel bio-products

• The vast diversity of bioactive capacities of marine natural products described

• Marine microorganisms as a source of environmentally friendly sunscreens

The chemistry and biology of fungal meroterpenoids (2009-2019)

Fungal meroterpenoids are secondary metabolites from mixed terpene-biosynthetic origins. Their intriguing chemical structural diversification and complexity, potential bioactivities, and pharmacological significance make them attractive targets in natural product chemistry, organic synthesis, and biosynthesis. This review provides a systematic overview of the isolation, chemical structural features, biological activities, and fungal biodiversity of 1585 novel meroterpenoids from 79 genera terrestrial and marine-derived fungi including macrofungi, Basidiomycetes, in 441 research papers in 2009-2019. Based on the nonterpenoid starting moiety in their biosynthesis pathway, meroterpenoids were classified into four categories (polyketide-terpenoid, indole-, shikimate-, and miscellaneous-) with polyketide-terpenoids (mainly tetraketide-) and shikimate-terpenoids as the primary source. Basidiomycota produced 37.5% of meroterpenoids, mostly shikimate-terpenoids. The genera of Ganoderma, Penicillium, Aspergillus, and Stachybotrys are the four dominant producers. Moreover, about 56% of meroterpenoids display various pronounced bioactivities, including cytotoxicity, enzyme inhibition, antibacterial, anti-inflammatory, antiviral, antifungal activities. It's exciting that several meroterpenoids including antroquinonol and 4-acetyl antroquinonol B were developed into phase II clinically used drugs. We assume that the chemical diversity and therapeutic potential of these fungal meroterpenoids will provide biologists and medicinal chemists with a large promising sustainable treasure-trove for drug discovery.

Marine Sponge-Associated Fungi as Potential Novel Bioactive Natural Product Sources for Drug Discovery: A Review

Marine sponge-associated fungi are promising sources of structurally interesting and bioactive secondary metabolites. Great plenty of natural products have been discovered from spongeassociated fungi in recent years. Here reviewed are 571 new compounds isolated from marine fungi associated with sponges in 2010-2018. These molecules comprised eight different structural classes, including alkaloids, polyketides, terpenoids, meroterpenoids, etc. Moreover, most of these compounds demonstrated profoundly biological activities, such as antimicrobial, antiviral, cytotoxic, etc. This review systematically summarized the structural diversity, biological function, and future potential of these novel bioactive natural products for drug discovery.

Antibacterial phenylspirodrimanes from the marine-derived fungus Stachybotrys sp. SCSIO 40434

Five new phenylspirodrimanes, stachybomycins A - E (1-5), together with four known compounds (6-9), were isolated from the marine-derived fungus Stachybotrys sp. SCSIO 40434. Their structures were elucidated by comprehensive spectroscopic analyses of NMR and HRESIMS. The absolute configuration of 1 was confirmed by single crystal X-ray diffraction analysis. Compounds 5 and 7 showed moderate antibacterial activities against Micrococcus luteus, Staphylococcus aureus and methicillin resistant Staphylococcus aureus with minimal inhibition concentration (MIC) values of 8, 16 and 16 μg mL^-1, respectively.

Impact of SMTP Targeting Plasminogen and Soluble Epoxide Hydrolase on Thrombolysis, Inflammation, and Ischemic Stroke

Stachybotrys microspora triprenyl phenol (SMTP) is a large family of small molecules derived from the fungus S. microspora. SMTP acts as a zymogen modulator (specifically, plasminogen modulator) that alters plasminogen conformation to enhance its binding to fibrin and subsequent fibrinolysis. Certain SMTP congeners exert anti-inflammatory effects by targeting soluble epoxide hydrolase. SMTP congeners with both plasminogen modulation activity and anti-inflammatory activity ameliorate various aspects of ischemic stroke in rodents and primates. A remarkable feature of SMTP efficacy is the suppression of hemorrhagic transformation, which is exacerbated by conventional thrombolytic treatments. No drug with such properties has been developed yet, and SMTP would be the first to promote thrombolysis but suppress disease-associated bleeding. On the basis of these findings, one SMTP congener is under clinical study and development. This review summarizes the discovery, mechanism of action, pharmacological activities, and development of SMTP.

Small double-stranded RNA with anti-HIV activity abundantly produced by Bacillus subtilis MTCC5480 isolated from fermented soybean

Anti-viral RNA therapy is on high demand nowadays due to the emergence of several new viral infections. The small non-coding regulatory RNAs (dsRNA) from the microbial sources are not yet explored for anti-viral activity. In this study, we assessed the anti-HIV activity of the small dsRNA produced by 12 different microbial species isolated from naturally fermented foods of North-East India. For this, we selectively extracted the dsRNA from the microbial culture, confirmed its double-stranded nature by immunoblotting, and deep sequenced the cDNA library using Illumina platform. Further, we used conventional algorithms to predict the potential targets of the dsRNA sequences within the 3'-UTR region of HIV-1. A small dsRNA fragment with 34 bases in size with a sequence of 3'-UUGGUACACGAGAUGGUUCGACUCGAUGAAGGGC-5' produced abundantly (9.17% of the total dsRNA fraction) by Bacillus subtilis MTCC5480 showed a much higher base complementarity values than previously reported miRNAs analysed against HIV-1. We separated the dsRNA fraction and validated the anti-HIV activity against human peripheral blood mononuclear cells (PBMC) infected with JRCSF strain of HIV-1 virus and the EC50 value ranges from 0.2-0.3 μM. This small dsRNA abundantly produced by B. subtilis could be studied further for its application as an anti-viral therapeutic agent.

Meroterpenoids produced by fungi: Occurrence, structural diversity, biological activities, and their molecular targets

Meroterpenoids are partially derived from the terpenoids, distributing widely in the plants, animals and fungi. The complex structures and diverse bioactivities of meroterpenoids have attracted more attention for chemists and pharmacologists. Since the first review summarized by Geris in 2009, there are absent of systematic reviews reported about meroterpenoids from the higher and lower fungi up to now. In the past decades, myriads of meroterpenoids were discovered, and it is necessary to summarize these meroterpenoids about their unique structures and promising bioactivities. In this review, we use a new classification method based on the non-terpene precursors, and also highlight the structural features, bioactivity of natural meroterpenoids from the higher and lower fungi covering the period of September 2008 to February 2020. A total of 709 compounds were discussed and cited the 182 references. Meanwhile, we also primarily summarize their occurrence, structural diversity, biological activities, and molecular targets.

1-Isoindolinone scaffold-based natural products with a promising diverse bioactivity

Isoindolin-1-one or 1-isoindolinone framework is referred to phthalimidines or benzo fused γ-lactams of the corresponding γ-amino carboxylic acids and has been of prime interest for scientists for last several decades. 1-Isoindolinone framework is found in a wide range of naturally occurring compounds with diverse biological activities and therapeutic potential for various chronic diseases. Recent developments in synthetic methods for their procurement have opened a new era of 1-isoindolinone chemistry. This review aims to provide an alphabetical quick reference guide to only 1-isoindolinone based natural products and its variable fused, oxidized and reduced state skeleton with information for advanced chemotaxonomic analyses, cellular targets/pathways and diverse biological activities and future use for medicinal chemistry.

Ten-Year Research Update Review: Antiviral Activities from Marine Organisms

Oceans cover more than 70 percent of the surface of our planet and are characterized by huge taxonomic and chemical diversity of marine organisms. Several studies have shown that marine organisms produce a variety of compounds, derived from primary or secondary metabolism, which may have antiviral activities. In particular, certain marine metabolites are active towards a plethora of viruses. Multiple mechanisms of action have been found, as well as different targets. This review gives an overview of the marine-derived compounds discovered in the last 10 years. Even if marine organisms produce a wide variety of different compounds, there is only one compound available on the market, Ara-A, and only another one is in phase I clinical trials, named Griffithsin. The recent pandemic emergency caused by SARS-CoV-2, also known as COVID-19, highlights the need to further invest in this field, in order to shed light on marine compound potentiality and discover new drugs from the sea.

Chartarlactams Q-T, Dimeric Phenylspirodrimanes with Antibacterial and Antiviral Activities

Four new phenylspirodrimane-type dimers, namely chartarlactams Q-T, along with stachyin B were isolated from the fermentation broth of a sponge-derived fungus Stachybotrys chartarum WGC-25 C-6. Chartarlactams Q-T were structurally featured by the dimerization of two units of phenylspirodrimane linked by a C-N bond. Their structures were determined on the basis of extensive spectroscopic analysis, while quantum ECD calculation and modified Mosher's method were used for the assignment of absolute configurations. Chartarlactams Q-S and stachyin B showed moderate inhibition against bacterial pathogen Staphylococcus aureus with MIC values ranging from 4 μg/mL to 16 μg/mL, and chartarlactam T exhibited significant inhibition toward ZIKV virus.

Bistachybotrysin K, one new phenylspirodrimane dimer from Stachybotrys chartarum with potent cytotoxic activity

Bistachybotrysin K (1), one new phenylspirodrimane dimer with a central 6/7 oxygen heterocycle core, was isolated from the fungus Stachybotrys chartarum CGMCC 3.5365. Its structure was elucidated by extensive spectroscopic data and single-crystal X-ray diffraction. Compound 1 showed significant cytotoxicity against human tumor cell lines HCT116, NCI-H460, BGC823, Daoy, and HepG2 with IC₅₀ values in the range of 1.1-4.7 µM.

Discovery, synthesis, and optimization of an N-alkoxy indolylacetamide against HIV-1 carrying NNRTI-resistant mutations from the Isatis indigotica root

From an aqueous decoction of the traditional Chinese medicine "ban lan gen" (the Isatis indigotica root), an antiviral natural product CI - 39 was isolated as an NNRTI (non-nucleoside reverse transcriptase inhibitor) (EC50 = 3.40 μM). Its novel structure was determined as methyl (1-methoxy-1H-indol-3-yl)acetamidobenzoate by spectroscopic data and confirmed by single crystal X-ray diffraction. Through synthesis and structure-activity relationship (SAR) investigation of CI - 39 and 57 new derivatives (24 with EC50 values of 0.06-8.55 μM), two optimized derivatives 10f and 10i (EC50: 0.06 μM and 0.06 μM) having activity comparable to that of NVP (EC50 = 0.03 μM) were obtained. Further evaluation verified that 10f and 10i were RT DNA polymerase inhibitors and exhibited better activities and drug resistance folds compared to NVP against seven NNRTI-resistant strains carrying different mutations. Especially, 10i (EC50 = 0.43 μM) was more active to the L100I/K103N double-mutant strain as compared to both NVP (EC50 = 0.76 μM) and EFV (EC50 = 1.08 μM). The molecular docking demonstrated a possible binding pattern between 10i and RT and revealed activity mechanism of 10i against the NNRTI-resistant strains.

Biological and Chemical Diversity of Marine Sponge-Derived Microorganisms over the Last Two Decades from 1998 to 2017

Marine sponges are well known as rich sources of biologically natural products. Growing evidence indicates that sponges harbor a wealth of microorganisms in their bodies, which are likely to be the true producers of bioactive secondary metabolites. In order to promote the study of natural product chemistry and explore the relationship between microorganisms and their sponge hosts, in this review, we give a comprehensive overview of the structures, sources, and activities of the 774 new marine natural products from sponge-derived microorganisms described over the last two decades from 1998 to 2017.

Glycosylated Natural Products From Marine Microbes

A growing body of evidence indicates that glycosylated natural products have become vital platforms for the development of many existing first-line drugs. This review covers 205 new glycosides over the last 22 years (1997-2018), from marine microbes, including bacteria, cyanobacteria, and fungi. Herein, we discuss the structures and biological activities of these compounds, as well as the details of their source organisms.

Bistachybotrysins L–V, bioactive phenylspirodrimane dimers from the fungus Stachybotrys chartarum

Bistachybotrysins L–V (1–11), eleven novel dimeric phenylspirodrimanes, were isolated from the fungus Stachybotrys chartarum CGMCC 3.5365.

Secondary Metabolites from Marine-Derived Fungi from China

Marine-derived fungi play an important role in the search for structurally unique secondary metabolites, some of which show promising pharmacological activities that make them useful leads for drug discovery. Marine natural product research in China in general has made enormous progress in the last two decades as described in this chapter on fungal metabolites. This contribution covers 613 new natural products reported from 2001 to 2017 from marine-derived fungi obtained from algae, sponges, corals, and other marine organisms from Chinese waters. The genera Aspergillus (170 new natural products, 28%) and Penicillium (70 new natural products, 11%) were the main fungal producers of new natural products during the time period covered, whereas sponges (184 new natural products, 30%) were the most abundant source of new natural products, followed by corals (154 new natural products, 25%) and algae (130 new natural products, 21%). Close to 40% of all natural products covered in this contribution displayed various bioactivities. The major bioactivities reported were cytotoxicity against different cancer cell lines, antimicrobial (mainly antibacterial) activity, and antiviral activity, which accounted for 13%, 9%, and 3% of all natural products reported. In terms of structural classes, polyketides (188 new natural products, 31%) play a dominant role, and if prenylated polyketides and nitrogen-containing polyketides (included in meroterpenes and alkaloids in this contribution) are taken into account, their total number even exceeds 50%. Nitrogen-containing compounds including peptides (65 new natural products, 10%) and alkaloids (103 new natural products, 17%) are the second largest group.

Natural disesquiterpenoids: an update

This review highlights the progress on the isolation, bioactivity, biogenesis and total synthesis of dimeric sesquiterpenoids since 2010.

Phenylspirodrimane Derivatives From Cultures of the Fungus Stachybotrys chartarum YIM DT 10079

A new phenylspirodrimane derivative, stachartin F (1), and 2 known secondary metabolites stachybonoid E (2) and stachybonoid F (3) were isolated from cultures of the tin mine tailings-associated fungus Stachybotrys chartarum YIM DT 10079. Their structures were determined with the help of extensive spectroscopic analyses and absolute configuration of compound 1 was rationalized by quantum chemical calculations of the electronic circular dichroism spectra.

Novel Antiretroviral Structures from Marine Organisms

In spite of significant advancements and success in antiretroviral therapies directed against HIV infection, there is no cure for HIV, which scan persist in a human body in its latent form and become reactivated under favorable conditions. Therefore, novel antiretroviral drugs with different modes of actions are still a major focus for researchers. In particular, novel lead structures are being sought from natural sources. So far, a number of compounds from marine organisms have been identified as promising therapeutics for HIV infection. Therefore, in this paper, we provide an overview of marine natural products that were first identified in the period between 2013 and 2018 that could be potentially used, or further optimized, as novel antiretroviral agents. This pipeline includes the systematization of antiretroviral activities for several categories of marine structures including chitosan and its derivatives, sulfated polysaccharides, lectins, bromotyrosine derivatives, peptides, alkaloids, diterpenes, phlorotannins, and xanthones as well as adjuvants to the HAART therapy such as fish oil. We critically discuss the structures and activities of the most promising new marine anti-HIV compounds.

Isolation, Structure Elucidation, and Total Synthesis of Myrtuspirone A from Myrtus communis

A pair of enantiomeric triketone-phloroglucinol hybrids, (+)- and (-)-myrtuspirone A (1), featuring an unprecedented 3-isopropyl-3 H-spiro[benzofuran-2,1'-cyclohexane] backbone, were isolated from the leaves of Myrtus communis. The absolute configuration of each enantiomer of 1 was determined by X-ray diffraction and chemical calculations. Furthermore, the gram-scale total syntheses of (±)-1 and (-)-1 were conducted in four steps using a Michael- N-iodosuccinimide (NIS)-mediated (3 + 2)-annulation reaction. Both (+)- and (-)-1 exhibited antibacterial activities against Gram-positive bacteria including multidrug-resistant strains.

Discovery of a semi-synthesized cyclolignan as a potent HIV-1 non-nucleoside reverse transcriptase inhibitor

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are essential components of highly active antiretroviral therapy (HAART) for human immunodeficiency virus type 1 (HIV-1) infection. In this study, we identified (+)-(7'S,8S,8'S)-3',4,4',5,5'-pentamethoxy-2,7'-cyclolignan (SG-1), a cyclolignan semi-synthesized from Machilus robusta and M. wangchiana extracts, as a potent NNRTI. SG-1 displayed anti-HIV-1 activity with an IC₅₀ of 0.77 μmol/L by inhibiting reverse transcriptase (RT) RNA-dependent DNA polymerase activity through a direct binding. It had synergistic effects when combined with tenofovir/lamivudine or zidovudine/lamivudine. The pharmacodynamics properties of SG-1 render it a valuable lead for the development of novel NNRTIs.

Pathogenic Viruses Commonly Present in the Oral Cavity and Relevant Antiviral Compounds Derived from Natural Products

Many viruses, such as human herpesviruses, may be present in the human oral cavity, but most are usually asymptomatic. However, if individuals become immunocompromised by age, illness, or as a side effect of therapy, these dormant viruses can be activated and produce a variety of pathological changes in the oral mucosa. Unfortunately, available treatments for viral infectious diseases are limited, because (1) there are diseases for which no treatment is available; (2) drug-resistant strains of virus may appear; (3) incomplete eradication of virus may lead to recurrence. Rational design strategies are widely used to optimize the potency and selectivity of drug candidates, but discovery of leads for new antiviral agents, especially leads with novel structures, still relies mostly on large-scale screening programs, and many hits are found among natural products, such as extracts of marine sponges, sea algae, plants, and arthropods. Here, we review representative viruses found in the human oral cavity and their effects, together with relevant antiviral compounds derived from natural products. We also highlight some recent emerging pharmaceutical technologies with potential to deliver antivirals more effectively for disease prevention and therapy.

A novel multivalent DNA helix-based inhibitor showed enhanced anti-HIV-1 fusion activity

DNA helix-based HIV-1 fusion inhibitors have been discovered as potent drug candidates, but further research is required to enhance their efficiency. The trimeric structure of the HIV-1 envelope glycoprotein provides a structural basis for multivalent drug design. In this work, a "multi-domain" strategy was adopted for design of an oligodeoxynucleotide with assembly, linkage, and activity domains. Built on the self-assembly of higher-order nucleic acid structure, a novel category of multivalent DNA helix-based HIV-1 fusion inhibitor could be easily obtained by a simple annealing course in solution buffer, with no other chemical synthesis for multivalent connection. An optimized multivalent molecule, M4, showed significantly higher anti-HIV-1 fusion activity than did corresponding monovalent inhibitors. Examination of the underlying mechanism indicated that M4 could interact with HIV-1 glycoproteins gp120 and gp41, thereby inhibiting 6HB formation in the fusion course. M4 also showed anti-RDDP and anti-RNase H activity of reverse transcriptase. Besides, these assembled molecules showed improved in vitro metabolic stability in liver homogenate, kidney homogenate, and rat plasma. Moreover, little acute toxicity was observed. Our findings aid in the structural design and understanding of the mechanisms of DNA helix-based HIV-1 inhibitors. This study also provides a general strategy based on a new structural paradigm for the design of other multivalent nucleic acid drugs.

Antiviral Agents From Fungi: Diversity, Mechanisms and Potential Applications

Viral infections are amongst the most common diseases affecting people worldwide. New viruses emerge all the time and presently we have limited number of vaccines and only few antivirals to combat viral diseases. Fungi represent a vast source of bioactive molecules, which could potentially be used as antivirals in the future. Here, we have summarized the current knowledge of fungi as producers of antiviral compounds and discuss their potential applications. In particular, we have investigated how the antiviral action has been assessed and what is known about the molecular mechanisms and actual targets. Furthermore, we highlight the importance of accurate fungal species identification on antiviral and other natural products studies.

Design, synthesis and biological evaluation of substituted (+)-SG-1 derivatives as novel anti-HIV agents

SG-1 was previously identified as a potent Non-nucleoside reverse transcriptase inhibitors (NNRTI) which works through inhibition of reverse transcriptase (RT) RNA-dependent DNA polymerase activity via a direct binding event. To further investigate the relationship between its structure and activity, four series of novel analogues were designed and synthesized with 12 of them inhibiting HIV-1 replication with IC₅₀s in the range 0.09-6.71 μM. Compound 4b, 4c, 4f, 2 and 6b were further tested on two NNRTI-resistant HIV-1 strains and one NNRTI-resistant superbug. The result showed that RT- E138K/M184V mutant virus conferred 4.7-9.1-fold resistance to 4c, 4f, 2 and 6b, but only showed slight resistance to 4b (2-fold) which was better than SG-1.

Antiviral Agents From Fungi: Diversity, Mechanisms and Potential Applications

Viral infections are amongst the most common diseases affecting people worldwide. New viruses emerge all the time and presently we have limited number of vaccines and only few antivirals to combat viral diseases. Fungi represent a vast source of bioactive molecules, which could potentially be used as antivirals in the future. Here, we have summarized the current knowledge of fungi as producers of antiviral compounds and discuss their potential applications. In particular, we have investigated how the antiviral action has been assessed and what is known about the molecular mechanisms and actual targets. Furthermore, we highlight the importance of accurate fungal species identification on antiviral and other natural products studies.

A new phenylspirodrimane dimer from the fungus Stachybotrys chartarum

A new phenylspirodrimane dimer, named stachartarin A (1), was isolated from cultures of the tin mine tailings-associated fungus Stachybotrys chartarum. Its structures were elucidated by means of spectroscopic methods. At the same time, the compound was tested for its cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cells.

Oxazole-Containing Diterpenoids from Cell Cultures of Salvia miltiorrhiza and Their Anti-HIV-1 Activities

Four new oxazole-containing diterpenoids, salvianans A-D (1-4), along with three known diterpenoids (5-7), were isolated from Salvia miltiorrhiza cell cultures. The structures of the new compounds were elucidated using spectroscopic methods and single-crystal X-ray diffraction. The evaluation for their anti-HIV-1 activities revealed that 2 and 3 displayed inhibitory activities with IC₅₀ values of 0.03 and 1.2 μM, respectively. The time of addition (TOA) assay and long terminal repeat (LTR) luciferase reporter assay results indicated that compound 2 was an HIV-1 transcription inhibitor and might be a lead compound of antiviral agents acting on HIV-1 transcription.

An Overview on Marine Sponge-Symbiotic Bacteria as Unexhausted Sources for Natural Product Discovery

Microbial symbiotic communities of marine macro-organisms carry functional metabolic profiles different to the ones found terrestrially and within surrounding marine environments. These symbiotic bacteria have increasingly been a focus of microbiologists working in marine environments due to a wide array of reported bioactive compounds of therapeutic importance resulting in various patent registrations. Revelations of symbiont-directed host specific functions and the true nature of host-symbiont interactions, combined with metagenomic advances detecting functional gene clusters, will inevitably open new avenues for identification and discovery of novel bioactive compounds of biotechnological value from marine resources. This review article provides an overview on bioactive marine symbiotic organisms with specific emphasis placed on the sponge-associated ones and invites the international scientific community to contribute towards establishment of in-depth information of the environmental parameters defining selection and acquisition of true symbionts by the host organisms.