Microsphaerins A–D, four novel benzophenone dimers with activity against MRSA from the fungus Microsphaeropsis sp

Secondary Metabolites from Fungi Microsphaeropsis spp.: Chemistry and Bioactivities

Microsphaeropsis, taxonomically classified within the kingdom fungi, phylum Ascomycota, subphylum Deuteromycotina, class Coelomycetes, order Sphaeropsidales, and family Sphaeropsidaceae, exhibit a ubiquitous distribution across various geographical regions. These fungi are known for their production of secondary metabolites, characterized by both structural novelty and potent biological activity. Consequently, they represent a significant reservoir for the advancement of novel pharmaceuticals. In this paper, a systematic review was present, marking the analysis of secondary metabolites synthesized by Microsphaeropsis reported between 1980 and 2023. A total of 112 compounds, comprising polyketones, macrolides, terpenoids, and nitrogen-containing compounds, were reported from Microsphaeropsis. Remarkably, among these compounds, 49 are novel discoveries, marking a significant contribution to the field. A concise summary of their diverse biological activities was provided, including antibacterial, antitumor, and antiviral properties and other bioactivities. This analysis stands as a valuable reference, poised to guide further investigations into the active natural products derived from Microsphaeropsis and their potential contributions to the development of medicinal resources.

Benzophenones-natural metabolites with great Hopes in drug discovery: structures, occurrence, bioactivities, and biosynthesis

Fungi have protruded with enormous development in the repository of drug discovery, making them some of the most attractive sources for the synthesis of bio-significant and structural novel metabolites. Benzophenones are structurally unique metabolites with phenol/carbonyl/phenol frameworks, that are separated from microbial and plant sources. They have drawn considerable interest from researchers due to their versatile building blocks and diversified bio-activities. The current work aimed to highlight the reported data on fungal benzophenones, including their structures, occurrence, and bioactivities in the period from 1963 to April 2023. Overall, 147 benzophenones derived from fungal source were listed in this work. Structure activity relationships of the benzophenones derivatives have been discussed. Also, in this review, a brief insight into their biosynthetic routes was presented. This work could shed light on the future research of benzophenones.

Two Antimicrobial Heterodimeric Tetrahydroxanthones with a 7,7'-Linkage from Mangrove Endophytic Fungus Aspergillus flavus QQYZ

Mangrove endophytic fungi represent significant and sustainable sources of novel metabolites with unique structures and excellent biological activities, attracting extensive chemical investigations. In this research, two novel heterodimeric tetrahydroxanthones, aflaxanthones A (1) and B (2), dimerized via an unprecedented 7,7′-linkage, a sp³-sp³ dimeric manner, were isolated from the mangrove endophytic fungus Aspergillus flavus QQYZ. Their structures were elucidated through high resolution electrospray ionization mass spectroscopy (HRESIMS) and nuclear magnetic resonance (NMR) spectroscopy, the absolute configurations of them were determined by a single-crystal X-ray diffraction combined with calculated electronic circular dichroism (ECD) spectra and a 1D potential energy scan. These compounds were evaluated for antifungal activities in vitro and exhibited broad-spectrum and potential antifungal activities against several pathogenic fungi with minimum inhibitory concentration (MIC) values in the range of 3.13–50 μM. They also performed moderate antibacterial activities against several bacteria with MIC values in the range of 12.5–25 μM. This research enriched the resources of lead compounds and templates for marine-derived antimicrobial drugs.

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Identification and engineering of 32 membered antifungal macrolactone notonesomycins

Notonesomycin A is a 32-membered bioactive glycosylated macrolactone known to be produced by Streptomyces aminophilus subsp. notonesogenes 647-AV1 and S. aminophilus DSM 40186. In a high throughput antifungal screening campaign, we identified an alternative notonesomycin A producing strain, Streptomyces sp. A793, and its biosynthetic gene cluster. From this strain, we further characterized a new more potent antifungal non-sulfated analogue, named notonesomycin B. Through CRISPR–Cas9 engineering of the biosynthetic gene cluster, we were able to increase the production yield of notonesomycin B by up to 18-fold as well as generate a strain that exclusively produces this analogue.

Nidulaxanthone A, a xanthone dimer with a heptacyclic 6/6/6/6/6/6/6 ring system from Aspergillus sp.-F029

Nidulaxanthone A (1), a xanthone dimer bearing an unprecedented heptacyclic 6/6/6/6/6/6/6 system, together with a new monomeric nidulalin D (2) and four known analogues (3, 4, 5 and 6), were isolated from Aspergillus sp. F029.

Syntheses of benzophenone-xanthone hybrid polyketides and their antibacterial activities

Muchimangins are benzophenone-xanthone hybrid polyketides produced by Securidaca longepedunculata. However, their biological activities have not been fully investigated, since they are minor constituents in this plant. To evaluate the possibility of muchimangins as antibacterial agent candidates, five muchimangin analogs were synthesized from 2,4,5-trimethoxydiphenyl methanol and the corresponding xanthones, by utilizing p-toluenesulfonic acid monohydrate for the Brønsted acid-catalysis. The antibacterial assays against Gram-positive bacteria, Staphylococcus aureus and Bacillus subtilis, and Gram-negative bacteria, Klebsiella pneumoniae and Escherichia coli, revealed that the muchimangin analogs (±)-1,3,6,8-tetrahydroxy-4-(phenyl-(2',4',5'-trimethoxyphenyl)methyl)-xanthone (1), (±)-1,3,6-trihydroxy-4-(phenyl-(2',4',5'-trimethoxyphenyl)methyl)-xanthone (2), and (±)-1,3-dihydroxy-4-(phenyl-(2',4',5'-trimethoxyphenyl)methyl)-xanthone (3) showed significant activities against S. aureus, with MIC values of 10.0, 10.0, and 25.0μM, respectively. Analogs (±)-1 and (±)-2 also exhibited antibacterial activities against B. subtilis, with MIC values of 50.0 and 12.5μM, respectively. Furthermore, (+)-3 enhanced the antibacterial activity against S. aureus, with a MIC value of 10μM.

Structural diversity and bioactivities of natural benzophenones

Natural benzophenones are a class of compounds with more than 300 members, mainly in the Clusiaceae family. We review key benzophenones, and provide an in-depth discussion of their great structural diversity and biological activity.

Arundinols A-C and arundinones A and B from the plant endophytic fungus Microsphaeropsis arundinis

Three new ent-eudesmane sesquiterpenoids, arundinols A-C (1-3), one isochroman-1-one, arundinone A (4), and a polyoxygenated benzofuran-3(2H)-one dimer, arundinone B (5), were isolated from the extract of a plant endophytic fungus, Microsphaeropsis arundinis. Their structures were elucidated primarily by NMR experiments, and 1 was confirmed by X-ray crystallography. The absolute configuration of 1 was assigned by X-ray crystallography using Cu Kα radiation, whereas those of the C-11 tertiary alcohols in 2 and 3 were deduced via the circular dichroism data of the in situ formed [Rh(2)(OCOCF(3))(4)] complexes. Arundinone B (5) represents the first dimeric benzofuran-3(2H)-one, showing cytotoxicity against T24 and A549 cells. The co-isolated known compound 6 showed a modest inhibitory effect against Staphylococcus aureus.

Phomalevones A-C: dimeric and pseudodimeric polyketides from a fungicolous Hawaiian isolate of Phoma sp. (Cucurbitariaceae)

Phomalevones A-C (1-3), three new com-pounds with bis-dihydroxanthone and bis-benzophenone systems, were isolated from cultures of a Hawaiian isolate of Phoma sp. (MYC-1734 = NRRL 39060; Cucurbitariaceae). The structures of 1-3 were determined by analysis of NMR and MS data. The absolute configurations of the sp(3) stereocenters in the monomeric unit of 1 were assigned by application of Mosher's method, and overall absolute configurations were proposed on the basis of ECD data using both computational methods and comparisons with literature data for model compounds. All three compounds showed antibacterial activity, and compounds 2 and 3 also exhibited antifungal effects.