Acremonidins F–H and acremoxanthones F–G, antimicrobial substances from the insect fungus Verticillium sp. BCC33181

Jugiones A-D: Antibacterial Xanthone-Anthraquinone Heterodimers from Australian Soil-Derived Penicillium shearii CMB-STF067

The Australian roadside soil-derived fungus Penicillium shearii CMB-STF067 was prioritized for chemical investigation based on an SDA cultivation extract exhibiting both antibacterial properties and natural products with unprecedented molecular formulae (GNPS). Subsequent miniaturized 24-well plate cultivation profiling (MATRIX) identified red rice as optimal for the production of the target chemistry, with scaled-up cultivation, extraction and fractionation yielding four new xanthone-anthraquinone heterodimers, jugiones A-D (1-4), whose structures were assigned by detailed spectroscopic analysis and biosynthetic considerations. Of note, where 1-2 and 4 were active against the Gram-positive bacteria vancomycin-resistant Enterococcus faecalis (IC50 2.6-3.9 μM) and multiple-drug-resistant clinical isolates of Staphylococcus aureus (IC50 1.8-6.4 μM), and inactive against the Gram-negative bacteria Escherichia coli (IC50 > 30 μM), the closely related analog 3 exhibited no antibacterial properties (IC50 > 30 μM). Furthermore, where 1 was cytotoxic to human carcinoma (IC50 9.0-9.8 μM) and fungal (IC50 4.1 μM) cells, 2 and 4 displayed no such cytotoxicity (IC50 > 30 μM), revealing an informative structure activity relationship (SAR). We also extended the SAR study to other known compounds of this heterodimer class, which showed that the modification of ring G can reduce or eliminate the cytotoxicity while retaining the antibacterial activity.

Appraisal of Fungus-Derived Xanthoquinodins as Broad-Spectrum Anti-Infectives Targeting Phylogenetically Diverse Human Pathogens

Xanthoquinodins make up a distinctive class of xanthone-anthraquinone heterodimers reported as secondary metabolites from several fungal species. Through a collaborative multi-institutional screening program, a fungal extract prepared from a Trichocladium sp. was identified that exhibited strong inhibitory effects against several human pathogens (Mycoplasma genitalium, Plasmodium falciparum, Cryptosporidium parvum, and Trichomonas vaginalis). This report focuses on one of the unique samples that exhibited a desirable combination of biological effects: namely, it inhibited all four test pathogens and demonstrated low levels of toxicity toward HepG2 (human liver) cells. Fractionation and purification of the bioactive components and their congeners led to the identification of six new compounds [xanthoquinodins NPDG A1-A5 (1-5) and B1 (6)] as well as several previously reported natural products (7-14). The chemical structures of 1-14 were determined based on interpretation of their 1D and 2D NMR, HRESIMS, and electronic circular dichroism (ECD) data. Biological testing of the purified metabolites revealed that they possessed widely varying levels of inhibitory activity against a panel of human pathogens. Xanthoquinodins A1 (7) and A2 (8) exhibited the most promising broad-spectrum inhibitory effects against M. genitalium (EC50 values: 0.13 and 0.12 μM, respectively), C. parvum (EC50 values: 5.2 and 3.5 μM, respectively), T. vaginalis (EC50 values: 3.9 and 6.8 μM, respectively), and P. falciparum (EC50 values: 0.29 and 0.50 μM, respectively) with no cytotoxicity detected at the highest concentration tested (HepG2 EC50 > 25 μM).

Identification of Substances Produced by Cercospora brachiata in Absence of Light and Evaluation of Antibacterial Activity

Cercospora brachiata is a phytopathogenic fungus. To know more about the metabolites produced by this fungus, the objective of this work was to identify, isolate and characterize substances present in extracts of the growth broth and mycelium, using gas chromatography with mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR). It was also objective to evaluate the antibacterial activity of the extracts. Among the compounds identified, fatty acids, esters, and steroids can be highlighted. The main compounds identified are 9-hexadecenoic, hexadecenoic, oleic, octadecanoic, lauric, myristic, palmitic, doceno-13-enoic, stearic, linoleic, and nonadecanoic acids present in almost all extracts. For the antibacterial activity, the broth microdilution method was used. The ethyl acetate extract of the mycelium presented inhibitory concentrations (MICs) against the bacterium Actinomyces naeslundii (100 μg mL^-1) and Streptococcus sanguinis (200 μg mL^-1). Finally, two steroids were isolated and identified in the hexane extract of mycelium: ergosta-6,22-dien-3β,5α,8α-triol and brassicasterol.

Role of bioactive metabolites from Acremonium camptosporum associated with the marine sponge Aplysina fulva

Acremonium camptosporum, a fungus associated with the marine sponge Aplysina fulva, was collected from the isolated mid-Atlantic Saint Peter and Saint Paul Archipelago, Brazil, and was found to produce secondary metabolites that displayed antibacterial activities. Mass spectra data obtained by UPLC-ESI-MS/MS analyses of these extracts were compared to several databases and revealed the presence of several different cytotoxic acremonidins and acremoxanthones. The close association between the sponge and the fungi with its compounds could be of strategic importance in defending both from the high predation pressure and spatial competition in the warm-water scarps of the islands.

Recent progress of antibacterial natural products: Future antibiotics candidates

The discovery of novel antibacterial molecules plays a key role in solving the current antibiotic crisis issue. Natural products have long been an important source of drug discovery. Herein, we reviewed 256 natural products from 11 structural classes in the period of 2016-01/2020, which were selected by SciFinder with new compounds or new structures and MICs lower than 10 μg/mL or 10 μM as criterions. This review will provide some effective antibacterial lead compounds for medicinal chemists, which will promote the antibiotics research based on natural products to the next level.

Antimicrobial activity and cytotoxicity of xanthoquinodin analogs from the fungus Cytospora eugeniae BCC42696

Eleven previously undescribed compounds, including cytosporanthraxanthone, xanthoquinodins A7-A10, ketoxanthoquinodin A6, xanthoquinodins B6-B8, and spiroxanthoquinodins A and B, and one synthetically known compound, 2-methoxy pinselin, as well as ten known compounds, including xanthoquinodins A4-A6, B4, and B5, chrysophanol, physcion, (4S)-5-hydroxy-4-methoxy-α-tetralone, (4S)-4,8-dihydroxy-α-tetralone (or isosclerone), and gonytolide C were isolated from the fungus Cytospora eugeniae BCC42696. Their chemical structures were determined based on the analysis of NMR spectroscopic and mass spectrometric data. Moreover, the absolute configurations of the unknown compounds were established by using NOESY and NOEDIFF NMR experiments along with CD spectroscopic data. The isolated xanthoquinodins exhibited a broad range of antimalarial, antibacterial, and fungicidal activities as well as cytotoxicity. Xanthoquinodins A6, B4, and B5 showed strong activity to Plasmodium falciparum, K1 strain (IC₅₀ 0.52-0.92 μM) and displayed anti-Bacillus cereus (MIC 1.56 μg/mL). Xanthoquinodin A6 also showed anti-Curvularia lunata (MIC 3.13 μg/mL). In addition, xanthoquinodins A4, A6, B4, and B5 and ketoxanthoquinodin A6 showed cytotoxicity against both cancerous (MCF-7, KB, NCI-H187) and non-cancerous (Vero) cells.

A Concise Approach to Anthraquinone-Xanthone Heterodimers

A synthetic approach to anthraquinone-xanthone heterodimers is described. The route to the pentacyclic core features an efficient assembly of a benzocycloheptenone via a new intramolecular oxidative arylation of an enol ether and a Hauser-Kraus annulation-aldol reaction sequence to access the characteristic bicyclo[3.2.2]nonene motif. Acremoxanthone A is synthesized in 10 steps from commercially available material to demonstrate the application of this approach.