Alkaloids from the endophytic fungus Penicillium brefeldianum and their cytotoxic activities

Prenylated indole diketopiperazine alkaloids as phosphatase inhibitors from the marine-derived fungus Talaromyces purpureogenus

Six previously undescribed prenylated indole diketopiperazine alkaloids, talaromyines A-F (1-6), were isolated from the marine-derived fungus Talaromyces purpureogenus SCSIO 41517. Their structures including absolute configurations were elucidated on the basis of comprehensive spectroscopic data including NMR, HR-ESI-MS, and electronic circular dichroism calculations, together with chemical analysis of hydrolysates. Compounds 1-5 represent the first example of spirocyclic indole diketopiperazines biosynthesized from the condensation of L-tryptophan and L-alanine. Compounds 2 and 4-5 showed selective inhibitory activities against phosphatases TCPTP and MEG2 with IC50 value of 17.9-29.7 μM, respectively. Compounds 4-5 exhibited mild cytotoxic activities against two human cancer cell lines H1975 and HepG-2.

Recent Advances in the Total Synthesis of Spirotryprostatin Alkaloids

Spirotryprostatin alkaloids, a class of alkaloids with a unique spirocyclic indoledionepiperazine structure, were first extracted from the fermentation broth of Aspergillus fumigatus and have garnered significant attention in the fields of biology and pharmacology. The investigation into the pharmacological potential of this class of alkaloids has unveiled promising applications in drug discovery and development. Notably, certain spirotryprostatin alkaloids have demonstrated remarkable anti-cancer activity, positioning them as potential candidates for anti-tumor drug development. In recent years, organic synthetic chemists have dedicated efforts to devise efficient and viable strategies for the total synthesis of spirotryprostatin alkaloids, aiming to meet the demands within the pharmaceutical domain. The construction of the spiro-C atom within the spirotryprostatin scaffold and the chirality control at the spiro atomic center emerge as pivotal aspects in the synthesis of these compounds. This review categorically delineates the synthesis of spirotryprostatin alkaloids based on the formation mechanism of the spiro-C atom.

Anti-diabetic and anti-inflammatory indole diterpenes from the marine-derived fungus Penicillium sp. ZYX-Z-143

Seven new indole-diterpenoids, penpaxilloids A-E (1-5), 7-methoxypaxilline-13-ene (6), and 10-hydroxy-paspaline (7), along with 20 known ones (8-27), were isolated from the marine-derived fungus Penicillium sp. ZYX-Z-143. Among them, compound 1 was a spiro indole-diterpenoid bearing a 2,3,3a,5-tetrahydro-1H-benzo[d]pyrrolo[2,1-b][1,3]oxazin-1-one motif. Compound 2 was characterized by a unique heptacyclic system featuring a rare 3,6,8-trioxabicyclo[3.2.1]octane unit. The structures of the new compounds were established by extensive spectroscopic analyses, NMR calculations coupled with the DP4 + analysis, and ECD calculations. The plausible biogenetic pathway of two unprecedented indole diterpenoids, penpaxilloids A and B (1 and 2), was postulated. Compound 1 acted as a noncompetitive inhibitor against protein tyrosine phosphatase 1B (PTP1B) with IC50 value of 8.60 ± 0.53 μM. Compound 17 showed significant α-glucosidase inhibitory activity with IC50 value of 19.96 ± 0.32 μM. Moreover, compounds 4, 8, and 22 potently suppressed nitric oxide production on lipopolysaccharide-stimulated RAW264.7 macrophages.

The potential of marine-derived piperazine alkaloids: Sources, structures and bioactivities

Marine-derived piperazine alkaloids (MDPAs) constitute a significant group of natural compounds known for their diverse structures and biological activities. Over the past five decades, substantial efforts have been devoted to isolating these alkaloids from marine sources and characterizing their chemical and bioactive profiles. To date, a total of 922 marine-derived piperazine alkaloids have been reported from various marine organisms. These compounds demonstrate a wide range of pharmacological properties, including cytotoxicity, antibacterial, antifungal, antiviral, and various other activities. Notably, among these activities, cytotoxicity emerges as the most prominent characteristic of marine-derived piperazine alkaloids. This review also summarizes the structure-activity relationship (SAR) studies associated with the cytotoxicity of these compounds. In summary, our objective is to provide an overview of the research progress concerning marine-derived piperazine alkaloids, with the aim of fostering their continued development and utilization.

Diketopiperazine and isoindolinone alkaloids from the endophytic fungus Aspergillus sp. HAB10R12

Four previously undescribed alkaloids, aspergillinine A-D, and four known diterpene pyrones were isolated from the potato dextrose agar (PDA) culture of Aspergillus sp. HAB10R12. The chemical structures of the isolated compounds were elucidated based on a detailed analysis of their NMR and MS data. The absolute configuration of the isolated compounds was determined by Electronic Circular Dichroism analysis coupled with computational methods. Aspergillinine A represents the first example of a diketopiperazine dipeptide containing the unnatural amino acid N-methyl kynurenine. Its absolute configuration revealed that it adopts a rather unusual conformation. Aspergillinine B represents a previously unencountered skeleton containing an isoindolinone ring. Aspergillinine C and D were similar to previously isolated diketopiperazine alkaloids, namely, lumpidin and brevianamide F, respectively. The diterpene pyrones were isolated twice previously, once from a soil-derived Aspergillus species, and once from the liquid culture of Aspergillus sp. HAB10R12. The alkaloids isolated in this study showed no antiproliferative activity when tested against HepG2 and A549 cancer cell lines.

A Saprophytic Fungus Tubeufia rubra Produces Novel Rubracin D and E Reversing Multidrug Resistance in Cancer Cells

Two new (1, 2 viz Rubracin D and E) and sixteen known Glyceroglycolipids (3–18) in the saprophytic fungus Tubeufia rubra (PF02-2) from decaying wood in freshwater habitat were isolated and identified. Their chemical structures were elucidated via means of the extensive spectroscopic analyses of NMR, HR-ESI-MS and UV spectra, as well as comparison with literature data. The new compounds were assayed for the reversal activity of multidrug resistance (MDR) on MCF-7/ADM, K562/ADM and A549/ADM cell lines, and both compounds 1 and 2 reversed MDR in the three resistant cancer cell lines with concentration dependence. In the assay on K562/ADM, both new compounds had been proved to have remarkable MDR reversal effects, which were higher than those of the positive control viz Verapamil (Vrp). Meanwhile, in the assay on A549/ADM, compound 1 displayed significant MDR reversal effects, which were also higher than those of Vrp at certain concentrations. Furthermore, the Western blot assay proved that both new compounds reversed the MDR in the resistant cancer cell line viz MCF-7/ADM by inhibiting the overexpression of P-glycoprotein. This is the first report that the Glyceroglycolipids isolated firstly from the fungal genus Tubeufia reversed MDR in resistant cancer cells.

Indole diketopiperazine alkaloids and aromatic polyketides from the Antarctic fungus Penicillium sp. SCSIO 05705

A new indole diketopiperazine alkaloid, named penilline D (1), together with five known indole alkaloid analogues (2-5, 11), two meroterpenoids (6 and 12), and four butenolide derivatives (7-10), were isolated from the Antarctic fungus Penicillium sp. SCSIO 05705. Extensive spectroscopic analysis and electronic circular dichroism (ECD) calculation were used to elucidate the structure of penilline D (1), including its absolute configuration. All isolated compounds (1-12) were evaluated for their cytotoxic, antibacterial and enzyme inhibitory activities against acetylcholinesterase (AChE) and pancreatic lipase (PL). Among them, compound 5 exhibited moderate in vitro cytotoxic activity against the 143B cell line with IC₅₀ value of 12.64 ± 0.78 μM. Compound 6 showed strong inhibitory activity against AChE with IC₅₀ value of 0.36 nM (IC₅₀ 18.7 nM for Tacrine), while compounds 6 and 11 showed weak PL enzyme inhibitory activity. Furthermore, an in silico molecular docking study was also performed between 6 and AChE.

Secondary Metabolites of Endophytes Associated with the Zingiberaceae Family and Their Pharmacological Activities

Zingiberaceae is commonly known as the ginger family and has been extensively studied in the last decades for its pharmacological purposes. The study of ginger includes microorganisms known as endophytes, which raise interest for the research community because they can produce a wide range of secondary metabolites. This review discusses the secondary metabolites of endophytes from the Zingiberaceae family and their pharmacological activities. We detail the group of secondary metabolites, updated for its absolute structures, source and part origins, and, especially, pharmacological divided properties. Zingiberaceae endophytes have 106 volatile compounds and 52 isolated constituents, including 17 polyketides, five nonribosomal peptides, five aromatic compounds, three alkaloids, and 21 terpene-alkaloids. They have antimicrobial, anticancer, antioxidant, and anti-inflammatory activities. Secondary metabolites from plant endophytes of the Zingiberaceae family have the potential to be therapeutic drugs in the future. Research on endophytic bacteria or fungi has been little performed. Therefore, this study supports a new drug discovery from Zingiberaceae endophytes and compares them for future drug development.

Metabolites from the plant endophytic fungus Penicillium sp. CPCC 401423 and their cytotoxic activity against MIA PaCa-2 cells

Twenty-two metabolites were isolated from Penicillium sp. CPCC 401423 cultured on rice. The structures of all compounds were elucidated mainly by MS and NMR analysis as well as the necessary CD experimental evidence, of which penicillidione A (1), penicillidione B (2), (E)-4-[(4-acetoxy-3-methyl-2-butenyl)oxy]phenylacetic acid (3), (S)-2-hydroxy-2-{4-[(3-methyl-2-butenyl)oxy]phenyl} (4), (S)-4-(2,3-dihydroxy-3-methyl-butoxy)phenylacetic acid (5), (E)-4-[(3-carboxy-2-butenyl)oxy]benzoic acid (6), (Z)-4-[(4-hydroxy-3-methyl-2-butenyl)oxy]benzoic acid (7), open-cycled N-demethylmelearoride A (12), and penostatin M (16) were identified as new compounds. The cytotoxic activity against human pancreatic carcinoma cell line MIA PaCa-2a was detected. Among them, compounds 13-15 and 22 displayed significant cytotoxicity against MIA-PaCa-2 cells with IC₅₀ values of 8.9, 36.5, 31.8, and 22.3 µM, respectively (positive control gemcitabine IC₅₀ 65.0 µM).

ECD exciton chirality method today: a modern tool for determining absolute configurations

The application of the exciton chirality method (ECM) to interpret electronic circular dichroism (ECD) spectra is a well‐established and still popular approach to assign the absolute configuration (AC) of natural products, chiral organic compounds, and organometallic species. The method applies to compounds containing at least two chromophores with electric dipole allowed transitions (e.g., π–π* transitions). The exciton chirality rule correlates the sign of an exciton couplet (two ECD bands with opposite sign and similar intensity) with the overall molecular stereochemistry, including the AC. A correct application of the ECM requires three main prerequisites: (a) the knowledge of the molecular conformation, (b) the knowledge of the directions of the electric transition moments (TDMs), and (c) the assumption that the exciton coupling mechanism must be the major source of the observed ECD signals. All these prerequisites can be easily verified by means of quantum‐mechanical (QM) calculations. In the present review, we shortly introduce the general principles that underpin the use of the ECM for configurational assignments and survey its applications, both classic ones and some reported in the recent literature. Based on these examples, we will stress the advantages of the ECM but also the key requisites for its correct application. Additionally, we will discuss the dependence of the couplet sign on geometrical parameters (angles α,β,γ between TDMs), which can be helpful for discerning the sign of exciton chirality in ambiguous situations. Finally, we will present a molecular orbital (MO) description of the exciton coupling phenomenon.

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.

Untargeted Metabolomics Approach for the Discovery of Environment-Related Pyran-2-ones Chemodiversity in a Marine-Sourced Penicillium restrictum

Very little is known about chemical interactions between fungi and their mollusc host within marine environments. Here, we investigated the metabolome of a Penicillium restrictum MMS417 strain isolated from the blue mussel Mytilus edulis collected on the Loire estuary, France. Following the OSMAC approach with the use of 14 culture media, the effect of salinity and of a mussel-derived medium on the metabolic expression were analysed using HPLC-UV/DAD-HRMS/MS. An untargeted metabolomics study was performed using principal component analysis (PCA), orthogonal projection to latent structure discriminant analysis (O-PLSDA) and molecular networking (MN). It highlighted some compounds belonging to sterols, macrolides and pyran-2-ones, which were specifically induced in marine conditions. In particular, a high chemical diversity of pyran-2-ones was found to be related to the presence of mussel extract in the culture medium. Mass spectrometry (MS)- and UV-guided purification resulted in the isolation of five new natural fungal pyran-2-one derivatives—5,6-dihydro-6S-hydroxymethyl-4-methoxy-2H-pyran-2-one (1), (6S, 1’R, 2’S)-LL-P880β (3), 5,6-dihydro-4-methoxy-6S-(1’S, 2’S-dihydroxy pent-3’(E)-enyl)-2H-pyran-2-one (4), 4-methoxy-6-(1’R, 2’S-dihydroxy pent-3’(E)-enyl)-2H-pyran-2-one (6) and 4-methoxy-2H-pyran-2-one (7)—together with the known (6S, 1’S, 2’S)-LL-P880β (2), (1’R, 2’S)-LL-P880γ (5), 5,6-dihydro-4-methoxy-2H-pyran-2-one (8), (6S, 1’S, 2’R)-LL-P880β (9), (6S, 1’S)-pestalotin (10), 1’R-dehydropestalotin (11) and 6-pentyl-4-methoxy-2H-pyran-2-one (12) from the mussel-derived culture medium extract. The structures of 1-12 were determined by 1D- and 2D-MMR experiments as well as high-resolution tandem MS, ECD and DP4 calculations. Some of these compounds were evaluated for their cytotoxic, antibacterial, antileishmanial and in-silico PTP1B inhibitory activities. These results illustrate the utility in using host-derived media for the discovery of new natural products.

New Purinyl-Steroid and Other Constituents from the Marine Fungus Penicillium brefeldianum ABC190807: Larvicidal Activities against Aedes aegypti

Mosquitoes historically threatened human health; the major mosquito-related global health issues include malaria, dengue fever, yellow fever, and Zika, as well as several other vector-borne outbreaks. Here, the EtOAc extract of the mangrove sediment fungus Penicillium brefeldianum ABC190807 exerted larvicidal activities against the third instar larvae of Aedes aegypti with an LC50 of 0.089 mg/mL. One new purinyl-steroid (ergosta-4,6,8(14),22-tetraen-3-(6-amino-9H-purin-9-yl) (1)), along with six (2–7) known compounds, were isolated from the EtOAc extract of Penicillium brefeldianum ABC190807. Structures of the compounds were elucidated via 1D/2D NMR and HR-ESI-MS data. Respective spectral data were compared with those of known compounds. Among all compounds whose larvicidal activity against the third instar larvae of Aedes aegypti was evaluated, compounds 2 and 7 showed larvicidal activity with respective LC50 values of 0.452 and 0.337 mg/mL.

Three new andrastin derivatives from the endophytic fungus Penicillium vulpinum

Three new andrastin derivatives, 10-formyl andrastone A (1), 10-demethylated andrastone A (2) and andrastin G (3), together with four known andrastin analogues (4-7) were isolated from an endophytic fungus Penicillium vulpinum. Their structures were determined by 1 D, 2 D NMR, and the absolute configurations were further determined by experimental and calculated ECD spectra. Compound 5 exhibited significant antibacterial activity against Bacillus paratyphosus B with an MIC value of 6.25 µg·mL^-1. Compounds 2 and 6 showed remarkable inhibitory activities against Bacillus megaterium with the MIC value of 6.25 µg·mL^-1, respectively.

A new antimicrobial indoloditerpene from a marine-sourced fungus aspergillus versicolor ZZ761

A new indoloditerpene (1) and fifteen known compounds (2-16) were isolated from a marine-derived fungus Aspergillus versicolor ZZ761. Structure of the new compound was elucidated as (3 R,9S,12R,13S,17S,18S)-2-carbonyl-3-hydroxylemeniveol based on its HRESIMS data, NMR spectroscopic analyses, the Mosher's method, and ECD calculation. This new indoloditerpene (1) showed antimicrobial activities with MIC values of 20.6 μM against Escherichia coli and 22.8 μM against Candida albicans. Diorcinol (2) and versicolorin B (6) had activities in inhibiting the proliferation of human glioma U87MG and U251 cells with IC₅₀ values of 4.4 and 6.2 μM and 11.3 and 30.5 μM, respectively.

Indole Diterpenoids from an Endophytic Penicillium sp

A chemical investigation of the endophyte Penicillium sp. (strain ZO-R1-1), isolated from roots of the medicinal plant Zingiber officinale, yielded nine new indole diterpenoids (1-9), together with 13 known congeners (10-22). The structures of the new compounds were elucidated by 1D and 2D NMR analysis in combination with HRESIMS data. The absolute configuration of the new natural products 1, 3, and 7 was determined using the TDDFT-ECD approach and confirmed for 1 by single-crystal X-ray determination through anomalous dispersion. The isolated compounds were tested for cytotoxicity against L5178Y, A2780, J82, and HEK-293 cell lines. Compound 1 was the most active metabolite toward L5178Y cells, with an IC₅₀ value of 3.6 μM, and an IC₅₀ against A2780 cells of 8.7 μM. Interestingly, 1 features a new type of indole diterpenoid scaffold with a rare 6/5/6/6/6/6/5 heterocyclic system bearing an aromatic ring C, which is suggested to be important for the cytotoxic activity of this natural product against L5278Y and A2780 cells.

Seven new cytotoxic phenylspirodrimane derivatives from the endophytic fungus Stachybotrys chartarum

Seven undescribed phenylspirodrimane derivatives, stachybochartins A–G (1–7), and four known analogues (8–11) were isolated from the endophytic fungus Stachybotrys chartarum obtained from Pinellia ternata. Stachybochartins A–D are four rare C–C-coupled dimeric derivatives and stachybochartin G features a seco-bisabosqual skeleton. Their structures and configurations were elucidated via spectroscopic analysis, electronic circular dichroism (ECD) calculations, the ECD exciton chirality method and the modified Mosher's method. Stachybochartins A–D and G displayed cytotoxic activities against MDA-MB-231 breast cancer cells and U-2OS osteosarcoma cells, with IC₅₀ values ranging from 4.5 to 21.7 μM. Stachybochartins C and G exerted strong anti-proliferative activities against U-2OS cells in concentration- and time-dependent manners and induced apoptosis.

The diverse structures and anticancer activities of phenylspirodrimane derivatives are investigated.

Novel natural compounds from endophytic fungi with anticancer activity

Plant endophytes are microorganisms that live in healthy plant tissues in part or all of their life history without causing obvious symptoms of infection in the host plants. Endophytes, a new type of microbial resource that can produce a variety of biological constituents, have great values for research and broad prospects for development. This article reviewed the research and development progress of endophytic fungi with cytotoxic activity between 2014 and 2017, including endophytic fungi sources, microbial taxonomy, compound classification and cytotoxic activity. The results showed that the 109 strains of endophytic fungi belong to 3 phyla, 7 classes and 50 genera. The secondary metabolites mainly contained alkaloids, terpenes, steroids, polyketides, quinones, isocoumarins, esters etc. The results of this study provide references for the development of new antitumor drugs and endophytes resources.

Polyketides from the fungus Penicillium decumbens

Two new polyketides, 3,11-dihydroxy-6,8-dimethyldodecanoic acid (1) and trichopyrone B (2), together with two known polyketides, sorbicillin (3) and penicillone A (4), have been isolated from the cultures broth of the fungus Penicillium decumbens. Their structures were elucidated by extensive spectroscopic analysis. All isolated compounds were evaluated for their antibacterial and cytotoxic activities. Of these, compound 3 showed antifungal activity toward Candida albicans Y0109 with a MIC value of 50 μM. Moreover, compounds 3 and 4 exhibited selective cytotoxicity against the human hepatocellular carcinoma (QGY-7703) cell line with the IC₅₀ values of 32.5 and 22.8 μM, respectively.

Endophytic Fungi-Alternative Sources of Cytotoxic Compounds: A Review

Cancer is a major cause of death worldwide, with an increasing number of cases being reported annually. The elevated rate of mortality necessitates a global challenge to explore newer sources of anticancer drugs. Recent advancements in cancer treatment involve the discovery and development of new and improved chemotherapeutics derived from natural or synthetic sources. Natural sources offer the potential of finding new structural classes with unique bioactivities for cancer therapy. Endophytic fungi represent a rich source of bioactive metabolites that can be manipulated to produce desirable novel analogs for chemotherapy. This review offers a current and integrative account of clinically used anticancer drugs such as taxol, podophyllotoxin, camptothecin, and vinca alkaloids in terms of their mechanism of action, isolation from endophytic fungi and their characterization, yield obtained, and fungal strain improvement strategies. It also covers recent literature on endophytic fungal metabolites from terrestrial, mangrove, and marine sources as potential anticancer agents and emphasizes the findings for cytotoxic bioactive compounds tested against specific cancer cell lines.

Structural Diversity and Biological Activities of the Cyclodipeptides from Fungi

Cyclodipeptides, called 2,5-diketopiperazines (2,5-DKPs), are obtained by the condensation of two amino acids. Fungi have been considered to be a rich source of novel and bioactive cyclodipeptides. This review highlights the occurrence, structures and biological activities of the fungal cyclodipeptides with the literature covered up to July 2017. A total of 635 fungal cyclodipeptides belonging to the groups of tryptophan-proline, tryptophan-tryptophan, tryptophan-Xaa, proline-Xaa, non-tryptophan-non-proline, and thio-analogs have been discussed and reviewed. They were mainly isolated from the genera of Aspergillus and Penicillium. More and more cyclodipeptides have been isolated from marine-derived and plant endophytic fungi. Some of them were screened to have cytotoxic, phytotoxic, antimicrobial, insecticidal, vasodilator, radical scavenging, antioxidant, brine shrimp lethal, antiviral, nematicidal, antituberculosis, and enzyme-inhibitory activities to show their potential applications in agriculture, medicinal, and food industry.