Two New Phenol Derivatives from the Cold Seep-Derived Fungus Aspergillus insuetus SD-512

Asperinsuterpenes A-C from the Fungus Aspergillus insuetus BTBU20220155

Three new meroterpenoids, asperinsuterpenes A-C (1-3), and eight previously reported natural products, namely asnovolin I (4), (2'E,4'E,6'E)-6-(1'-carboxyocta-2',4',6'-triene)-9-hydroxydrim-7-ene-11,12-olide (5), (2'E,4'E,6'E)-6-(1'-carboxyocta-2',4',6'-triene)-11,12-epoxy-9,11-dihydroxydrim-7-ene (6), cinereain (7), carnequinazolines A and B (8 and 9), carnemycin B (10), and stromemycin (11) were isolated from the fungus Aspergillus insuetus, strain BTBU20220155. The structures of the compounds were determined based on spectroscopic techniques, including 1D and 2D NMR, HRESIMS, and ECD experiments. The in vitro antimicrobial evaluation revealed that compounds 5 and 11 exhibited inhibitory activity against Candida albicans, with minimum inhibitory concentration (MIC) values of 12.5 and 25 μg/mL, respectively. These findings suggest that A. insuetus is a promising source of bioactive natural products with potential applications in antifungal therapy.

New Hydroxyphenylacetic Acids and α-Pyrone Derivative from the Deep-Sea Cold Seep Sediment-Derived Fungus Penicillium corylophilum CS-682

Two pairs of new enantiomeric hydroxyphenylacetic acid derivatives, (±)-corylophenols A and B ((±)-1 and (±)-2), a new α-pyrone analogue, corylopyrone A (3), and six andrastin-type meroterpenoids (4-9) were isolated and identified from the deep-sea cold-seep sediment-derived fungus Penicillium corylophilum CS-682. Their structures and stereo configurations were determined by detailed spectroscopic analysis of NMR and MS data, chiral HPLC analysis, J-based configuration analysis, and quantum chemical calculations of ECD, specific rotation, and NMR (with DP4+ probability analysis). Compound 3 showed inhibitory activity against some strains of pathogenic bacteria.

Aspertides A-E: Antimicrobial Pentadepsipeptides with a Unique p-Methoxycinnamoyl Amide Group from the Marine Isolates Aspergillus tamarii MA-21 and Aspergillus insuetus SD-512

Marine fungus-derived natural products are an important source of antimicrobial compounds against marine aquatic pathogens. Here, we describe the isolation and characterization of five new pentadepsipeptides, aspertides A-E (1-5), containing a unique p-methoxycinnamoyl amide group, from the marine fungi Aspergillus tamarii MA-21 and Aspergillus insuetus SD-512. Among them, aspertides B-E (2-5) also possessed uncommon amino acid residues, such as 3-hydroxyproline, 2,3-dihydroxyproline, or pipecolinic acid. The structures of these compounds were elucidated on the basis of NMR and mass spectroscopic analyses. The absolute configurations of them were established by chiral HPLC analyses of the acidic hydrolysates and NMR calculations with DP4+ probability analysis. In bio-activity assays, compounds 4 and 5 exhibited antibacterial activities against aquatic-pathogenic bacteria, including Edwardsiella tarda, Vibrio alginolyticus, Vibrio anguillarum, Vibrio vulnificus, and Staphylococcus aureus, with MIC values of 8-32 μg/mL.

Cyclohexenone Derivative and Drimane Sesquiterpenes from the Seagrass-Derived Fungus Aspergillus insuetus

One new cyclohexenone derivative (1), and two undescribed drimane sesquiterpenes (2 and 3), together with another seven known drimane sesquiterpenes were isolated from a seagrass-derived fungus Aspergillus insuetus SYSU6925. Structures of these metabolites were elucidated by comprehensive spectroscopic analysis, including NMR analysis, mass spectrometry, and ECD calculations. Compounds 1-3, 5 and 7 displayed weak to moderate antifungal activities towards four phytopathogenic fungi, with Minimum inhibition concentration (MIC) values range from 50 to 200 μg/mL. Compound 1, a rare cyclohexenone derivative with n-propyl group exhibited more potent inhibitory activities (MIC, 50 μg/mL) against F. oxysporum than positive control (Triadimefon). Compounds 2 and 3 also exhibit potent anti-inflammatory activities by inhibiting the production of nitric oxide (NO) in RAW264.7 cells with IC50 values of 21.5±1.1 and 32.6±1.16 μM, respectively.

Isolation and characterization of three pairs of verrucosidin epimers from the marine sediment-derived fungus Penicillium cyclopium and configuration revision of penicyrone A and related analogues

Verrucosidins, a methylated α-pyrone class of polyketides rarely reported upon, have been implicated in one or more neurological diseases. Despite the significance of verrucosidins as neurotoxins, the absolute configurations of most of the derivatives have not been accurately characterized yet. In this study, three pairs of C-9 epimeric verrucosidin derivatives, including the known compounds penicyrones A and B (1a/1b) and 9-O-methylpenicyrones A and B (2a/2b), the new compounds 9-O-ethylpenicyrones A and B (3a/3b), together with the related known derivative verrucosidin (4), were isolated and identified from the culture extract of Penicillium cyclopium SD-413, which was obtained from the marine sediment collected from the East China sea. Their structures were established based on an in-depth analysis of nuclear magnetic resonances (NMR) and mass spectroscopic data. Determination of the absolute configurations of these compounds was accomplished by Mosher's method and time-dependent density functional theory (TDDFT) calculations of electronic circular dichroism (ECD) and optical rotation (OR). The configurational assignment of penicyrone A demonstrated that the previously reported C-6 absolute configuration of verrucosidin derivatives needs to be revised from (6S) to (6R). The 9R/9S epimers of compounds 1-3 were found to exhibit growth inhibition against some pathogenic bacteria, indicating that they have potential as lead compounds for the creation of antimicrobial agents.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00173-2.

Disentangling the Functional Role of Fungi in Cold Seep Sediment

Cold seeps are biological oases of the deep sea fueled by methane, sulfates, nitrates, and other inorganic sources of energy. Chemolithoautotrophic bacteria and archaea dominate seep sediment, and their diversity and biogeochemical functions are well established. Fungi are likewise diverse, metabolically versatile, and known for their ability to capture and oxidize methane. Still, no study has ever explored the functional role of the mycobiota in the cold seep biome. To assess the complex role of fungi and fill in the gaps, we performed network analysis on 147 samples to disentangle fungal-prokaryotic interactions (fungal 18S and prokaryotic 16S) in the Haima cold seep region. We demonstrated that fungi are central species with high connectivity at the epicenter of prokaryotic networks, reduce their random-attack vulnerability by 60%, and enhance information transfer efficiency by 15%. We then scavenged a global metagenomic and metatranscriptomic data set from 10 cold seep regions for fungal genes of interest (hydrophobins, cytochrome P450s, and ligninolytic family of enzymes); this is the first study to report active transcription of 2,500+ fungal genes in the cold seep sediment. The genera Fusarium and Moniliella were of notable importance and directly correlated with high methane abundance in the sulfate-methane transition zone (SMTZ), likely due to their ability to degrade and solubilize methane and oils. Overall, our results highlight the essential yet overlooked contribution of fungi to cold seep biological networks and the role of fungi in regulating cold seep biogeochemistry. IMPORTANCE The challenges we face when analyzing eukaryotic metagenomic and metatranscriptomic data sets have hindered our understanding of cold seep fungi and microbial eukaryotes. This fact does not make the mycobiota any less critical in mediating cold seep biogeochemistry. On the contrary, many fungal genera can oxidize and solubilize methane, produce methane, and play a unique role in nutrient recycling via saprotrophic enzymatic activity. In this study, we used network analysis to uncover key fungal-prokaryotic interactions that can mediate methane biogeochemistry and metagenomics and metatranscriptomics to report that fungi are transcriptionally active in the cold seep sediment. With concerns over rising methane levels and cold seeps being a pivotal source of global methane input, our holistic understanding of methane biogeochemistry with all domains of life is essential. We ultimately encourage scientists to utilize state-of-the-art tools and multifaceted approaches to uncover the role of microeukaryotic organisms in understudied systems.

Anti-Vibrio potential of natural products from marine microorganisms

The emergence of drug-resistant Vibrio poses a serious threat to aquaculture and human health, thus there is an urgent need for the discovery of new related antibiotics. Given that marine microorganisms (MMs) are evidenced as important sources of antibacterial natural products (NPs), great attention has been gained to the exploration of potential anti-Vibrio agents from MMs. This review summarizes the occurrence, structural diversity, and biological activities of 214 anti-Vibrio NPs isolated from MMs (from 1999 to July 2022), including 108 new compounds. They were predominantly originated from marine fungi (63%) and bacteria (30%) with great structural diversity, including polyketides, nitrogenous compounds, terpenoids, and steroids, among which polyketides account for nearly half (51%) of them. This review will shed light on the development of MMs derived NPs as potential anti-Vibrio lead compounds with promising applications in agriculture and human health.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

Anti-inflammatory alkaloids from the cold-seep-derived fungus Talaromyces helicus SCSIO41311

One new natural alkaloid, chaetominine B (1), together with twenty known compounds was isolated from the South China Sea cold-seep-derived fungus Talaromyces helicus SCSIO41311. Their structures were elucidated on the basis of nuclear magnetic resonance spectrum (NMR), mass spectrometry (MS) and ECD calculation, as well as comparing with previous literatures. Among them, twelve compounds showed potent NO inhibitory activities and two of them, azaspirofurans A (13) and fumiquinones B (21), exhibited NO inhibitory effects more than the positive control eicosapentaenoic acid (EPA) with IC₅₀ values of 9.65 and 15.54 μM, respectively. Moreover, compound 13 attenuated LPS-induced imbalance of cytokines release such as TNF-α, IL-1β, IL-4, and IL-10. Additionally, the NMR data and absolute configuration of compound 20 were first reported.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03237-9.

New Cytochalasin Derivatives from Deep-Sea Cold Seep-Derived Endozoic Fungus Curvularia verruculosa CS-129

Two new antimicrobial cytochalasin derivatives, 6 β , 7 β -epoxydeoxaphomin C ( 1 ) and 12-hydroxydeoxaphomin C ( 2 ), a new natural occurring product 24-nor-cytochalasin B ( 3 ), together with two related known analogues ( 4 - 5 ) were isolated and identified from an endozoic fungus Curvularia verruculosa CS-129, isolated from the deep-sea squat lobster Shinkaia crosnieri which was collected in cold seep region of south China sea. The structures of new compounds were elucidated on the basis of detailed spectroscopic analysis and ECD calculation. The spectroscopic data of 24-nor-cytochalasin B ( 3 ) were reported for the first time. All compounds were tested for their antibacterial activities against human and aquatic pathogenic bacteria.

Deep-Sea Natural Products from Extreme Environments: Cold Seeps and Hydrothermal Vents

The deep sea has been proven to be a great treasure for structurally unique and biologically active natural products in the last two decades. Cold seeps and hydrothermal vents, as typical representatives of deep-sea extreme environments, have attracted more and more attention. This review mainly summarizes the natural products of marine animals, marine fungi, and marine bacteria derived from deep-sea cold seeps and hydrothermal vents as well as their biological activities. In general, there were 182 compounds reported, citing 132 references and covering the literature from the first report in 1984 up to March 2022. The sources of the compounds are represented by the genera Aspergillus sp., Penicillium sp., Streptomyces sp., and so on. It is worth mentioning that 90 of the 182 compounds are new and that almost 60% of the reported structures exhibited diverse bioactivities, which became attractive targets for relevant organic synthetic and biosynthetic studies.

Marine fungal metabolites as a source of drug leads against aquatic pathogens

Aquatic pathogens, including Vibrio, Edwardsiella, Pseudomonas, and Aeromonas, which could result in bacterial diseases to aquaculture, have seriously threatened the world aquaculture production. Marine-derived fungi, which could produce novel secondary metabolites with significant antibacterial activity, may be an important source for finding effective agents against aquatic pathogens. In this review, a systematically overview of the harm of several aquatic pathogens, and 134 antibacterial secondary metabolites against aquatic pathogens from 13 genera of marine-derived fungi, were summarized and concluded. The aim of this review is to find out the relationships between activity and structural type, between bioactive compounds and their hosts, and so on. Altogether, 95 references published during 1997-2021 were cited. KEY POINTS: •Aquatic pathogens, which could result in bacterial diseases to aquaculture, were described. •Marine fungal metabolites with activities against aquatic pathogens were summarized. •The distributions of these bioactive marine fungal metabolites were analyzed.

Chevalinulins A and B, Proangiogenic Alkaloids with a Spiro[bicyclo[2.2.2]octane-diketopiperazine] Skeleton from Deep-Sea Cold-Seep-Derived Fungus Aspergillus chevalieri CS-122

Chevalinulins A (1) and B (2), two indole diketopiperazine alkaloids containing an unprecedented spiro[bicyclo[2.2.2]octane-diketopiperazine] skeleton, together with a known analogue neoechinulin B (3), were isolated from the deep-sea cold-seep-derived fungus Aspergillus chevalieri CS-122. Their structures were determined by spectroscopic analysis, single-crystal X-ray diffraction, specific rotation (SR), and NMR calculations. Compounds 1 and 2 exhibited significant in vivo proangiogenic activity in transgenic zebrafish.

Acremocholone, an Anti-Vibrio Steroid from the Marine Mesophotic Zone Ciocalypta Sponge-Associated Fungus Acremonium sp. NBUF150

Mesophotic coral ecosystems (MCEs) represent an underexplored source of intriguing natural products. Efforts to discover bioactive metabolites from sponge-associated fungi in MCEs identified a new steroid, acremocholone (1) and its three known analogs (2-4), from Acremonium sp. NBUF150. The Acremonium sp. NBUF150 was isolated from a Ciocalypta sponge located 70 m deep within the South China Sea. The planar structures and absolute configuration of 1-4 were determined from NMR-derived spectroscopic data, HR-ESI-MS, and X-ray crystallography. Compound 1 exhibited antimicrobial inhibition against Vibrio scophthalmi, V. shilonii and V. brasiliensis at minimum inhibitory concentrations of 8 μg/mL; compound 2 inhibited V. shilonii and V. brasiliensis at 8 and 32 μg/mL, respectively, and compound 4 inhibited growth of V. brasiliensis at 16 μg/mL. Sponge associated fungi from MCEs represent a promising resource of anti-Vibrio drug leads for aquaculture use.