Discovery of (±)-Penindolenes Reveals an Unusual Indole Ring Cleavage Pathway Catalyzed by P450 Monooxygenase.

(±)-Penindolenes A-D (1-4), the first representatives of indole terpenoids featuring a γ-lactam skeleton, were isolated from the mangrove-derived endophytic fungus Penicillium brocae MA-231. Our bioactivity tests revealed their potent antimicrobial and acetylcholinesterase inhibitory activities. The biosynthetic reactions by the five enzymes PbaABCDE leading to γ-lactam ring formation were identified with heterologous expression and in vitro enzymatic assays. Remarkably, the cytochrome P450 monooxygenase PbaB and its homolog in Aspergillus oryzae  catalyzed the 2,3-cleavage of the indole ring to generate two keto groups in 1, in different manners from well-known tryptophan dioxygenases. This is the first example of the oxidative cleavage of indole by a P450 monooxygenase. In addition, rare secondary amide bond formation by the glutamine synthetase-like enzyme PbaD was reported. These findings will contribute to the engineered biosynthesis of unnatural, bioactive indole terpenoids.

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.

Pseudallenes A and B, new sulfur-containing ovalicin sesquiterpenoid derivatives with antimicrobial activity from the deep-sea cold seep sediment-derived fungus Pseudallescheria boydii CS-793.

Pseudallenes A and B (1 and 2), the new and rare examples of sulfur-containing ovalicin derivatives, along with three known analogues 3-5, were isolated and identified from the culture extract of Pseudallescheria boydii CS-793, a fungus obtained from the deep-sea cold seep sediments. Their structures were established by detailed interpretation of NMR spectroscopic and mass spectrometric data. X-ray crystallographic analysis confirmed and established the structures and absolute configurations of compounds 1-3, thus providing the first characterized crystal structure of an ovalicin-type sesquiterpenoid. In the antimicrobial assays, compounds 1-3 showed broad-spectrum inhibitory activities against several plant pathogens with MIC values ranging from 2 to 16 µg/mL.

Curvularin derivatives from the marine mangrove derived fungus Penicillium sumatrense MA-325.

Sumalarins D-G (1-4), four previously undescribed curvularin derivatives, along with two known related metabolites, curvularin (5) and dehydrocurvularin (6), were isolated and identified from the mangrove-derived fungus Penicillium sumatrense MA-325. Among them, sumalarin D (1) represents a unique example of curvularin derivative featuring a 5-methylfuran-2-yl-methyl group. Their structures were elucidated based on analysis of NMR and MS data as well as comparison of ECD spectra and quantum chemical calculations of NMR, and compound 1 was confirmed by X-ray crystallographic analysis. Compounds 1, 2, 5, and 6 are active against aquatic pathogenic bacteria Vibrio alginolyticus and V. harveyi with MIC values ranging from 4 to 64 µg/mL, while compound 6 is cytotoxic against tumor cell lines 5673, HCT 116, 786-O, and Hela with IC50 values of 3.5, 10.6, 10.9, and 14.9 µM, respectively.

Absolute Configuration of 12S-Deoxynortryptoquivaline from Ascidian-Derived Fungus Aspergillus clavatus Determined by Anisotropic NMR and Chiroptical Spectroscopy.

Tryptoquivalines are highly toxic metabolites initially isolated from the fungus Aspergillus clavatus. The relative and absolute configuration of tryptoquivaline derivates was primarily established by comparison of the chemical shifts, NOE data, and ECD calculations. A de novo determination of the complete relative configuration using NMR spectroscopy was challenging due to multiple spatially separated stereocenters, including one nonprotonated carbon. In this study, we isolated a new tryptoquivaline derivative, 12S-deoxynortryptoquivaline (1), from the marine ascidian-derived fungus Aspergillus clavatus AS-107. The correct assignment of the relative configuration of 1 was accomplished using anisotropic NMR spectroscopy, while the absolute configuration was determined by comparing calculated and experimental ECD spectra. This case study highlights the effectiveness of anisotropic NMR parameters over isotropic NMR parameters in determining the relative configuration of complex natural products without the need for crystallization.

Bialorastins A-F, highly oxygenated and polycyclic andrastin-type meroterpenoids with proangiogenic activity from the deep-sea cold-seep-derived fungus Penicillium bialowiezense CS-283.

Six new highly oxygenated and polycyclic andrastin-type meroterpenoids, namely, bialorastins A-F (1-6), were discovered from the culture of Penicillium bialowiezense CS-283, a fungus isolated from the deep-sea cold seep squat lobster Shinkaia crosnieri. The planar structures and absolute configurations of these compounds were determined by detailed analysis of spectroscopic data, single crystal X-ray diffraction, and TDDFT-ECD calculations. Structurally, bialorastin A (1) represents a rare 17-nor-andrastin that possesses an unusual 2-oxaspiro[4.5]decane-1,4-dione moiety with a unique 6/6/6/6/5 polycyclic system, while bialorastin B (2) is also a 17-nor-andrastin featuring a gem-propane-1,2-dione moiety. Additionally, bialorastins C-E (3-5) possess a 6/6/6/6/5/5 fused hexacyclic skeleton, characterized by distinctive 3,23-acetal/lactone-bridged functionalities. All isolated compounds were evaluated for their proangiogenic activities in transgenic zebrafish. Compound 3 exhibited significant proangiogenic activity, which notably increased the number and length of intersegmental blood vessels in model zebrafish in a dose-dependent manner at concentrations of 20 and 40 µM. On a molecular scale, the tested compounds were modeled through molecular docking to have insight into the interactions with the possible target VEGFR2. Mechanistically, RT-qPCR results revealed that compound 3 could promote angiogenesis via activating VEGFR2 and subsequently activating the downstream PI3K/AKT and MAPK signaling pathways. These findings indicate that 3 could be a potential lead compound for developing angiogenesis agents.

A new steroid with potent antimicrobial activities and two new polyketides from Penicillium variabile EN-394, a fungus obtained from the marine red alga Rhodomela confervoides.

Three new compounds, including one steroid named penivariod A (1) and two polyketides penivarides A and B (2 and 3), as well as six known derivatives (4-9) were isolated from Penicillium variabile EN-394, a fungus afforded from the marine red alga Rhodomela confervoides. Their structures were elucidated by analysis of the HRESIMS, 1D and 2D NMR. The absolute stereochemistry was determined by X-ray crystallographic data, gauge-independent atomic orbital (GIAO) NMR shift calculation followed by DP4+ analysis combined with calculated electronic circular dichroism (ECD). Antimicrobial activities for the new compounds (1-3) were evaluated against human- and aquatic-pathogenic bacteria as well as plant pathogenic fungi. Compound 1 exhibited potent antimicrobial activity against most of the pathogenic strains, especially for Escherichia coli and Pseudomonas aeruginosa, with MIC values of 1.0 and 2.0 µg ml-1, respectively.

Antimicrobial polyketides from Magellan Seamount-derived fungus Talaromyces scorteus AS-242.

Two new nonadride derivatives, namely, talarodrides G and H (1 and 2), and one new depsidone derivative, botryorhodine K (3), together with a known nonadride analogue (4), were characterized from the Magellan Seamount-derived fungus Talaromyces scorteus AS-242. Their structures were established by detailed interpretation of NMR spectroscopic and mass spectrometry data analysis. X-ray crystallographic analysis of compounds 1 and 3 confirmed their structures and absolute configurations, representing the first characterized crystal structure of a nonadride-type polyketide. The isolated compounds exhibited potent antimicrobial activities against the pathogenic bacterium MRSA and V. parahaemolyticus and pathogenic fungi C. gloeosporioides, F. oxysporum, and F. proliferatum, with MIC values ranging from 1 to 64 µg ml-1.

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.

Natural products with 1,2-oxazine scaffold: occurrence, chemical diversity, bioactivity, synthesis, and biosynthesis.

Covering: up to the end of July, 20231,2-Oxazine is a heterocyclic scaffold rarely found in natural products and is characterized by a directly connected N-O bond in a six-membered ring. Since the discovery of geneserine, the first 1,2-oxazine-containing natural product (1,2-oxazine NP) being isolated from Calabar bean (Physostigma venenosum) in 1925, a total of 76 naturally occurring 1,2-oxazine NPs have been isolated and identified from various sources, which have attracted the attention of researchers in the field of natural product chemistry, organic synthesis, biosynthesis, and pharmacology. This review summarizes the chemical family of 1,2-oxazine NPs, focusing on their source organisms, structural diversities, chemical synthesis, and biosynthesis.

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.

Oxepine-containing pyrazinopyrimidine alkaloids and quinolinone derivatives produced by Aspergillus versicolor AS-212, a deep-sea-derived endozoic fungus.

Four new oxepine-containing pyrazinopyrimidine alkaloids, versicoxepines A - D (1-4), two quinolinone alkaloid analogs including 3-hydroxy-6-methoxy-4-phenylquinolin-2(1H)-one (5) and 3-methoxy-6-hydroxy-4-phenylquinolin-2(1H)-one (6) which were new naturally occurring compounds, together with two known compounds (7 and 8) were isolated from Aspergillus versicolor AS-212, an endozoic fungus isolated from the deep-sea coral Hemicorallium cf. imperiale, which was collected from the Magellan Seamounts in the Western Pacific Ocean. Their structures were determined by extensive analysis of the spectroscopic and X-ray crystallographic data as well as by chiral HPLC analysis, ECD calculation, and DP4+ probability prediction. Structurally, versicoxepines B and C (2 and 3) represent the first example of a new oxepine-containing pyrazinopyrimidine alkaloid whose cyclic dipeptide moiety is composed of the same type of amino acid (Val or Ile). Compound 5 displayed antibacterial activity against aquatic pathogens, Vibrio harveyi and V. alginolyticus, with MICs of 8 µg/mL.

Diketopiperazine Alkaloids and Bisabolene Sesquiterpenoids from Aspergillus versicolor AS-212, an Endozoic Fungus Associated with Deep-Sea Coral of Magellan Seamounts.

Two new quinazolinone diketopiperazine alkaloids, including versicomide E (2) and cottoquinazoline H (4), together with ten known compounds (1, 3, and 5-12) were isolated and identified from Aspergillus versicolor AS-212, an endozoic fungus associated with the deep-sea coral Hemicorallium cf. imperiale, which was collected from the Magellan Seamounts. Their chemical structures were determined by an extensive interpretation of the spectroscopic and X-ray crystallographic data as well as specific rotation calculation, ECD calculation, and comparison of their ECD spectra. The absolute configurations of (-)-isoversicomide A (1) and cottoquinazoline A (3) were not assigned in the literature reports and were solved in the present work by single-crystal X-ray diffraction analysis. In the antibacterial assays, compound 3 exhibited antibacterial activity against aquatic pathogenic bacteria Aeromonas hydrophilia with an MIC value of 18.6 µM, while compounds 4 and 8 exhibited inhibitory effects against Vibrio harveyi and V. parahaemolyticus with MIC values ranging from 9.0 to 18.1 µM.

Rubensteroid A, a new steroid with antibacterial activity from Penicillium rubens AS-130.

A new steroid with strong antibacterial activity, rubensteroid A (1), along with its decarboxylic analogue, solitumergosterol A (2), were isolated and identified from the Magellan Seamount-derived fungus Penicillium rubens AS-130. The structure and absolute configuration of compound 1 were established by detailed interpretation of NMR spectroscopic analysis, mass spectrometry data, and TDDFT-ECD calculations. Compound 1 had a rare 6/6/6/6/5 pentacyclic system, which might be the [4 + 2] Diels-Alder adduct of 14,15-didehydroergosterol (14-DHE) cycloaddition with maleic acid or maleimide, followed by decarboxylation. Rubensteroid A (1) exhibited potent antibacterial activity against Escherichia coli and Vibrio parahaemolyticus, both with MIC value of 0.5 µg/mL.

Three new α-pyrone derivatives from the soil-derived fungus Penicillium herquei MA-370.

Three new α-pyrone derivatives, annularins L-N (1-3), were isolated from the EtOAc extract of Penicillium herquei MA-370, a fungus obtained from the rhizospheric soil of the mangrove plant Rhizophora mucronata. The planar structures of compounds 1-3 were determined based on comprehensive spectral interpretation of the NMR and MS data. The absolute configuration of 1 was determined by X-ray crystallographic data and that of 2 was assigned by TDDFT calculations of its ECD spectrum and cotton effects comparison with those of 1. The antimicrobial activity of compounds 1-3 was evaluated.

Bisabolane sesquiterpene and cyclopentene derivatives from the marine algal-derived endophytic fungus Trichoderma asperellum EN-764.

Four undescribed bisabolane sesquiterpenes and one undescribed cyclopentene derivative, together with one undescribed naturally occurring cyclopentenone derivative, were isolated and identified from the culture of the endophytic fungus Trichoderma asperellum EN-764, which was obtained from the marine red alga Palisada papillosa. Their structures were determined by detailed interpretation of NMR and mass spectroscopic data, while the relative and absolute configurations were unambiguously established based on NOESY experiments, modified Mosher's method, X-ray diffraction, and quantum chemical calculations (ECD and DP4+ probability analysis). The antibacterial activities of the isolated compounds were evaluated, and they exhibited inhibitory activity against some aquatic pathogens with MIC values ranging from 4 to 64 µg/mL.

Antibacterial Indole Diketopiperazine Alkaloids from the Deep-Sea Cold Seep-Derived Fungus Aspergillus chevalieri.

A large body of fungal secondary metabolites has been discovered to exhibit potent antibacterial activities with distinctive mechanisms and has the potential to be an untapped resource for drug discovery. Here, we describe the isolation and characterization of five new antibacterial indole diketopiperazine alkaloids, namely 24,25-dihydroxyvariecolorin G (1), 25-hydroxyrubrumazine B (2), 22-chloro-25-hydroxyrubrumazine B (3), 25-hydroxyvariecolorin F (4), and 27-epi-aspechinulin D (5), along with the known analogue neoechinulin B (6) from a fungal strain of deep-sea cold seep-derived Aspergillus chevalieri. Among these compounds, 3 and 4 represented a class of infrequently occurring fungal chlorinated natural products. Compounds 1-6 showed inhibitory activities against several pathogenic bacteria with MIC values ranging from 4 to 32 µg/mL. It was revealed that compound 6 could induce structural damage to the Aeromonas hydrophila cells based on the observation by scanning electron microscopy (SEM), which led to the bacteriolysis and death of A. hydrophila, suggesting that neoechinulin B (6) might be a potential alternative to novel antibiotics development.

New Polyketide and Sesquiterpenoid Derivatives from the Magellan Seamount-Derived Fungus Penicillium rubens AS-130.

Rubenpolyketone A (1), a polyketide featuring a new carbon skeleton having cyclohexenone condensed with a methyl octenone chain and a new linear sesquiterpenoid, chermesiterpenoid D (2), together with seven known secondary metabolites (3-9) were isolated and identified from the Magellan Seamount-derived fungus Penicillium rubens AS-130. Their structures were determined based on detailed analysis of NMR and mass spectroscopic data and the absolute configurations of these two new compounds were elucidated by the combination of quantum mechanical (QM)-NMR and time-dependent density functional (TDDFT) ECD calculation approaches. Chermesiterpenoids B (3) and C (4) showed potent inhibitory activities against the aquatic pathogen Vibrio anguillarum with MIC values of 0.5 and 1 µg/mL, respectively, while chermesin F (6) exhibited activity against Escherichia coli with MIC value of 1 µg/mL.

Antimicrobial polyketides and sesquiterpene lactones from the deep-sea cold-seep-derived fungus Talaromyces minioluteus CS-113 triggered by the histone deacetylase inhibitor SAHA.

Seven new highly oxygenated natural products with diverse chemical structural types, including three new glucosidic polyketides, talaminiosides A-C (1-3), a pair of racemic aromatic polyketides, (±)-talaminone A (4a and 4b), two new azaphilone polyketides, (+)-5-chloromitorubrinic acid (5) and 7-epi-purpurquinone C (7), and one new drimane sesquiterpene lactone, 11-hydroxyminioluteumide B (8), together with a pinazaphilone B sodium salt (6) and 10 known compounds (9-18), were isolated and identified from the culture extract of Talaromyces minioluteus CS-113, a fungus obtained from deep-sea cold-seep sediments collected from the South China Sea. LCMS results indicated that compounds 3 and 4 might be produced by the real activation of silent BGCs triggered by the histone deacetylase inhibitor SAHA, and some of the other compounds were enhanced minor components. Their structures were elucidated by the detailed interpretation of NMR spectroscopic and mass spectrometric data, X-ray crystallographic analysis, ECD and specific rotation (SR) calculations, and DP4+ probability analysis. Compound 7, an azaphilone derivative, exhibited potent activities against several agricultural pathogenic fungi with MIC values equivalent or comparable to amphotericin B. The structure-activity relationship of the isolated azaphilones is briefly discussed. This is the first report of the chemical diversity study of deep-sea cold-seep-derived fungi triggered by SAHA, providing a useful strategy for the activation of cryptic fungal metabolites from deep-sea-derived fungi.

Five new verrucosidin derivatives from Penicillium polonicum, a deep-sea cold-seep sediment isolated fungus.

Five new verrucosidin derivatives, poloncosidins G-K (1-5), were isolated from the deep sea cold-seep sediment-derived fungus Penicillium polonicum CS-252. Their planar structures were elucidated by discreet analysis of the NMR spectroscopic and HRESIMS spectrometric data. The absolute configurations of compounds 1-5 were deduced from the combination of the modified Mosher's method and quantum chemical calculations of their ECD and NMR (with DP4+ probability analysis) data. The antimicrobial activities against several human- and aquatic-pathogenic bacteria of all the isolated compounds were evaluated and the structure-bioactivity relationship was briefly discussed.