Marine-derived Aspergillus Sp Research Articles

Development of Marker Recycling Systems for Sequential Genetic Manipulation in Marine-Derived Fungi Spiromastix sp. SCSIO F190 and Aspergillus sp. SCSIO SX7S7.

Marine-derived fungi are emerging as prolific workhorses of structurally novel natural products (NPs) with diverse bioactivities. However, the limitation of available selection markers hampers the exploration of cryptic NPs. Recyclable markers are therefore valuable assets in genetic engineering programs for awaking silent SM clusters. Here, both pyrG and amdS-based recyclable marker cassettes were established and successfully applied in marine-derived fungi Aspergillus sp. SCSIO SX7S7 and Spiromastix sp. SCSIO F190, respectively. Using pyrG recyclable marker, a markerless 7S7-∆depH strain with a simplified HPLC background was built by inactivating a polyketide synthase (PKS) gene depH and looping out the pyrG recyclable marker after depH deletion. Meanwhile, an amdS recyclable marker system was also developed to help strains that are difficult to use pyrG marker. By employing the amdS marker, a backbone gene spm11 responsible for one major product of Spiromastix sp. SCSIO F190 was inactivated, and the amdS marker was excised after using, generating a relatively clean F190-∆spm11 strain for further activation of novel NPs. The collection of two different recycle markers will guarantee flexible application in marine-derived fungi with different genetic backgrounds, enabling the exploitation of novel structures in various fungi species with different genome mining strategies.

Research Advances of Bioactive Sesquiterpenoids Isolated from Marine-Derived Aspergillus sp.

Marine fungi Aspergillus sp. is an important source of natural active lead compounds with biological and chemical diversity, of which sesquiterpenoids are an extremely important class of bioactive secondary metabolites. In this paper, we review the sources, chemical structures, bioactivity, biosynthesis, and druggability evaluation of sesquiterpenoids discovered from marine fungi Aspergillus sp. since 2008. The Aspergillus species involved include mainly Aspergillus fumigatus, Aspergillus versicolor, Aspergillus flavus, Aspergillus ustus, Aspergillus sydowii, and so on, which originate from sponges, marine sediments, algae, mangroves, and corals. In recent years, 268 sesquiterpenoids were isolated from secondary metabolites of marine Aspergillus sp., 131 of which displayed bioactivities such as antitumor, antimicrobial, anti-inflammatory, and enzyme inhibitory activity. Furthermore, the main types of active sesquiterpenoids are bisabolanes, followed by drimanes, nitrobenzoyl, etc. Therefore, these novel sesquiterpenoids will provide a large number of potential lead compounds for the development of marine drugs.

Molecular Networking-Driven Discovery of Antibacterial Perinadines, New Tetracyclic Alkaloids from the Marine Sponge-Derived Fungus Aspergillus sp.

Two rare tetracyclic skeleton alkaloids named perinadines B and C (1 and 2) were isolated as mixtures of epimers from the marine-derived Aspergillus sp. LS116 driven by molecular networking. The planar structures of 1 and 2 were characterized by comprehensive spectroscopic data. Additionally, compounds 1 and 2 showed moderate in vitro antibacterial activity against Bacillus subtilis with minimum inhibitory concentration values of 32 and 64 μg/mL, respectively. Besides, both of the compounds were evaluated for anti-inflammatory activities in an in vivo zebra fish model.

A new diketopiperazine-like inhibitor of bone morphogenetic protein-induced osteoblastic differentiation produced by marine-derived Aspergillus sp. BFM-0085

A new diketopiperazine-like compound, designated protuboxepin K (1), was isolated together with the known structurally related protuboxepin A (2) from culture broth of the marine-derived fungal strain Aspergillus sp. BFM-0085 isolated from a sediment sample of Tokyo Bay. The structure of protuboxepin K was elucidated by spectroscopic data, including 1D and 2D NMR. Compounds 1 and 2 inhibited bone morphogenetic protein (BMP)-induced alkaline phosphatase activity with IC50 values of 4.7 and 25.2 μM, respectively, in mutant BMP receptor-carrying C2C12(R206H) cells.

Antitumor Activity of Asperphenin A, a Lipopeptidyl Benzophenone from Marine-Derived Aspergillus sp. Fungus, by Inhibiting Tubulin Polymerization in Colon Cancer Cells.

Marine-derived microorganisms are a valuable source of novel bioactive natural products. Asperphenin A is a lipopeptidyl benzophenone metabolite isolated from large-scale cultivation of marine-derived Aspergillus sp. fungus. The compound has shown potent antiproliferative activity against various cancer cells. However, the underlying mechanism of action remained to be elucidated. In this study, we demonstrated the antitumor activity and molecular mechanism of asperphenin A in human colon cancer cells for the first time. Asperphenin A inhibited the growth of colon cancer cells through G2/M cell cycle arrest followed by apoptosis. We further discovered that asperphenin A can trigger microtubule disassembly. In addition to its effect on cell cycle, asperphenin A-induced reactive oxygen species. The compound suppressed the growth of tumors in a colon cancer xenograft model without any overt toxicity and exhibited a combination effect with irinotecan, a topoisomerase I inhibitor. Moreover, we identified the aryl ketone as a key component in the molecular structure responsible for the biological activity of asperphenin A using its synthetic derivatives. Collectively, this study has revealed the antiproliferative and antitumor mechanism of asperphenin A and suggested its possibility as a chemotherapeutic agent and lead compound with a novel structure.

Absolute Configurations of 14,15-Hydroxylated Prenylxanthones from a Marine-Derived Aspergillus sp. Fungus by Chiroptical Methods

Determination of the absolute configrations for natural products is one of the most important and challenging tasks, especially when the molecules display high conformational flexibility. In this paper, eight new prenylxanthones, aspergixanthones A-H (1–8), and one known analogue (9), were isolated from the marine-derived fungus Aspergillus sp. ZA-01. The absolute configurations of C-14 and C-15 in 1–8 were difficult to be assigned due to the high conformational flexibility of the chains. To solve this problem, the experimental ECD, ORD, and VCD spectra of 1 were combined for analysis with the corresponding theoretical predictions for its different diastereomers. This study suggested that a concerted application of more than one chiroptical methods could be used as a preferable approach for the stereochemical characterizations of flexible molecules. Compounds 1–9 were evaluated for their cytotoxic and antibacterial activities. Among them, 6 showed cytotoxicity against the A-549 cell line with the IC50 value of 1.1 μM, and 7 exhibited antibacterial activity against Micrococcus lysodeikticus with the MIC value of 0.78 μg/mL.

Chemical constituents isolated from Antarctic marine-derived Aspergillus sp. SF-5976 and their anti-inflammatory effects in LPS-stimulated RAW 264.7 and BV2 cells

Three new benzaldehydes (1–3) and two new dioxopiperazine alkaloids (4 and 5), along with 23 known constituents, were isolated from Antarctic marine-derived Aspergillus sp. SF-5976. Their structures were determined by spectroscopic and chemical methods. Among them, 20 compounds showed inhibitory effects toward lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 macrophages with IC50 values of 7.3–77.4 μM, while 22 compounds did in BV2 microglia with those of 4.6–72.3 μM. Furthermore, the effects of the newly isolated compounds on LPS-stimulated inducible NO synthase (iNOS) expression were investigated, and 1–3, and 5 inhibited iNOS in RAW 264.7 cells, while 1–5 did in BV2 cells. Also, 1–3 and 5 inhibited LPS-induced prostaglandin E2 production with IC50 values of 9.1–66.8 μM in RAW 264.7 macrophages by suppressing cyclooxygenase-2 (COX-2), while in BV2 microglia, 1–5 showed activities with those of 2.8–49.4 μM.

Bioconversion of 6-epi-Notoamide T produces metabolites of unprecedented structures in a marine-derived Aspergillus sp.

We previously described the bioconversion of Notoamide T into (+)-Stephacidin A and (−)-Notoamide B, which suggested that Versicolamide B (8) is biosynthesized from 6-epi-Notoamide T (10) via 6-epi-Stephacidin A. Here we report that [13C]2-10 was incorporated into isotopically enriched 8 and seven new metabolites, which were not produced under normal culture conditions. The results suggest that the addition of excess precursor activated the expression of dormant tailoring genes giving rise to these structurally unprecedented metabolites.

Terretonin G, a new sesterterpenoid antibiotic from marine-derived Aspergillus sp. OPMF00272.

Terretonin G, a new sesterterpenoid antibiotic from marine-derived Aspergillus sp. OPMF00272

Study on the biosynthesis of the notoamides: pinacol-type rearrangement of the isoprenyl unit in deoxybrevianamide E and 6-hydroxydeoxybrevianamide E

Two reverse-prenylated indole alkaloids, deoxybrevianamide E and 6-hydroxydeoxybrevianamide E, are proposed as biosynthetic precursors for advanced metabolites isolated from the marine-derived Aspergillus sp. In order to uncover the role of the alkaloids in the biosynthetic pathway, the feeding experiments of the [13C]2–[15N]-labeled deoxybrevianamide E and 6-hydroxydeoxybrevianamide E were performed to afford the metabolites, which were produced by oxidation and successive pinacol-type rearrangement of the isoprenyl units.

ChemInform Abstract: Study on Natural Products for Drug Development

AbstractReview: 19 refs.

Study on Natural Products for Drug Development

The ubiquitin-proteasome system (UPS) plays a major role in selective protein degradation and regulates various cellular events. Approval of bortezomib for the treatment of multiple myeloma validated the proteasome as an anticancer target. In order to find drug candidates targeting the ubiquitin-dependent protein degradation, we paid an attention to inhibitors against three enzymes, ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzyme (E2), and ubiquitin-protein ligase (E3), which are required for polyubiquitination of proteins and prerequisite to proteasome-mediated protein degradation. We succeeded in isolating various compounds with three distinct inhibitory activities against an E1 enzyme reaction, Ubc13 (E2)-Uev1A interaction, and p53-HDM2 (E3) interaction as well as the proteasome inhibitors. We also isolated new alkaloids, notoamides, from a marine-derived Aspergillus sp. Among them, notoamide B and stephacidin A contain a bicyclo[2.2.2]diazaoctane ring in their structures. We proposed this ring is constructed from notoamide E by the intramolecular Diels-Alder (IMDA) reaction. Recently, the isolation of the antipodes of notoamides from the terrestrial Aspergillus has been reported. We propose that each enantiomer is generated by a distinct face-selective IMDA.

Genome-Based Characterization of Two Prenylation Steps in the Assembly of the Stephacidin and Notoamide Anticancer Agents in a Marine-Derived Aspergillus sp.

Stephacidin and notoamide natural products belong to a group of prenylated indole alkaloids containing a core bicyclo[2.2.2]diazaoctane ring system. These bioactive fungal secondary metabolites have a range of unusual structural and stereochemical features but their biosynthesis has remained uncharacterized. Herein, we report the first biosynthetic gene cluster for this class of fungal alkaloids based on whole genome sequencing of a marine-derived Aspergillus sp. Two central pathway enzymes catalyzing both normal and reverse prenyltransfer reactions were characterized in detail. Our results establish the early steps for creation of the prenylated indole alkaloid structure and suggest a scheme for the biosynthesis of stephacidin and notoamide metabolites. The work provides the first genetic and biochemical insights for understanding the structural diversity of this important family of fungal alkaloids.

Notoamide O, a Structurally Unprecedented Prenylated Indole Alkaloid, and Notoamides P−R from a Marine-Derived Fungus, Aspergillus sp.

Notoamides O-R were isolated from a marine-derived Aspergillus sp. Notoamide O possesses a novel hemiacetal/hemiaminal ether functionality hitherto unknown among this family of prenylated indole alkaloids. The structure represents an unusual branch point for the oxidative modification of other members in the family of prenylated indole alkaloids in the biogenetic pathway.

Isolation of Antipodal (−)-Versicolamide B and Notoamides L−N from a Marine-Derived Aspergillus sp.

Antipodal (-)-versicolamide B and notoamides L-N were isolated from a marine-derived Aspergillus sp. The possible biosynthetic pathway of enantiomeric pairs of notoamide B and versicolamide B are proposed. Notoamide L is the first metabolite containing 25 carbons in the related prenylated indole alkaloids. Notoamide M is potentially a precursor to the proposed azadiene species involved in the putative intramolecular Diels-Alder reaction in the biogenesis of the bicyclo[2.2.2]diazaoctane ring system.

Notoamides F−K, Prenylated Indole Alkaloids Isolated from a Marine-Derived Aspergillus sp.

Six new prenylated indole alkaloids, named notoamides F-K (8-13), were isolated from a marine-derived Aspergillus sp. Their structures, including absolute configurations, were elucidated by spectroscopic methods. Notoamide I (11) showed weak cytotoxicity against HeLa cells with an IC(50) value of 21 microg/mL.

Notoamides A–D: Prenylated Indole Alkaloids Isolated from a Marine‐Derived Fungus, Aspergillus sp.

Six new prenylated indole alkaloids, named notoamides F−K (8−13), were isolated from a marine-derived Aspergillus sp. Their structures, including absolute configurations, were elucidated by spectroscopic methods. Notoamide I (11) showed weak cytotoxicity against HeLa cells with an IC50 value of 21 μg/mL.