Chemical diversity, medicinal potentialities, biosynthesis, and pharmacokinetics of anthraquinones and their congeners derived from marine fungi: a comprehensive update

Carneusones A-F, Benzophenone Derivatives from Sponge-Derived Fungus Aspergillus carneus GXIMD00543

Six benzophenone derivatives, carneusones A-F (1-6), along with seven known compounds (7-13) were isolated from a strain of sponge-derived marine fungus Aspergillus carneus GXIMD00543. Their chemical structures were elucidated by detailed spectroscopic data and quantum chemical calculations. Compounds 5, 6, and 8 exhibited moderate anti-inflammatory activity on NO secretion using lipopolysaccharide (LPS)-induced RAW 264.7 cells with EC50 values of 34.6 ± 0.9, 20.2 ± 1.8, and 26.8 ± 1.7 μM, while 11 showed potent effect with an EC50 value of 2.9 ± 0.1 μM.

Naphthoquinone Derivatives from Angustimassarina populi CF-097565 Display Anti-Tumour Activity in 3D Cultures of Breast Cancer Cells

Cancer is one of the leading causes of death worldwide, with breast cancer being the second cause of cancer-related mortality among women. Natural Products (NPs) are one of the main sources for drug discovery. During a screening campaign focused on the identification of extracts from Fundación MEDINA's library inhibiting the proliferation of cancer cell lines, a significant bioactivity was observed in extracts from cultures of the fungus Angustimassarina populi CF-097565. Bioassay-guided fractionation of this extract led to the identification and isolation of herbarin (1), 1-hydroxydehydroherbarin (4) plus other three naphthoquinone derivatives of which 3 and 5 are new natural products and 2 is herein described from a natural source for the first time. Four of these compounds (1, 3, 4 and 5) confirmed a specific cytotoxic effect against the human breast cancer cell line MCF-7. To evaluate the therapeutic potential of the compounds isolated, their efficacy was validated in 3D cultures, a cancer model of higher functionality. Additionally, an in-depth study was carried out to test the effect of the compounds in terms of cell mortality, sphere disaggregation, shrinkage, and morphology. The cell profile of the compounds was also compared to that of known cytotoxic compounds with the aim to distinguish the drug mode of action (MoA). The profiles of 1, 3 and 4 showed more biosimilarity between them, different to 5, and even more different to other known cytotoxic agents, suggesting an alternative MoA responsible for their cytotoxicity in 3D cultures.

Microbial Pigments: Major Groups and Industrial Applications

Microbial pigments have many structures and functions with excellent characteristics, such as being biodegradable, non-toxic, and ecologically friendly, constituting an important source of pigments. Industrial production presents a bottleneck in production cost that restricts large-scale commercialization. However, microbial pigments are progressively gaining popularity because of their health advantages. The development of metabolic engineering and cost reduction of the bioprocess using industry by-products opened possibilities for cost and quality improvements in all production phases. We are thus addressing several points related to microbial pigments, including the major classes and structures found, the advantages of use, the biotechnological applications in different industrial sectors, their characteristics, and their impacts on the environment and society.

Exploring the Potential of Anthraquinone-Based Hybrids for Identifying a Novel Generation of Antagonists for the Smoothened Receptor in HH-Dependent Tumour

Natural products (NPs) are highly profitable pharmacological tools due to their chemical diversity and ability to modulate biological systems. Accessing new chemical entities while retaining the biological relevance of natural chemotypes is a fundamental goal in the design of novel bioactive compounds. Notably, NPs have played a crucial role in understanding Hedgehog (HH) signalling and its pharmacological modulation in anticancer therapy. However, HH antagonists developed so far have shown several limitations, thus growing interest in the design of second-generation HH inhibitors. Through smart manipulation of the NPs core-scaffold, unprecedented and intriguing architectures have been achieved following different design strategies. This study reports the rational design and synthesis of a first and second generation of anthraquinone-based hybrids by combining the rhein scaffold with variously substituted piperazine nuclei that are structurally similar to the active portion of known SMO antagonists, the main transducer of the HH pathway. A thorough functional and biological investigation identified RH2_2 and RH2_6 rhein-based hybrids as valuable candidates for HH inhibition through SMO antagonism, with the consequent suppression of HH-dependent tumour growth. These findings also corroborated the successful application of the NPs-based hybrid design strategy in the development of novel NP-based SMO antagonists.

Anthraquinone Derivatives and Other Aromatic Compounds from Marine Fungus Asteromyces cruciatus KMM 4696 and Their Effects against Staphylococcus aureus

New anthraquinone derivatives acruciquinones A-C (1-3), together with ten known metabolites, were isolated from the obligate marine fungus Asteromyces cruciatus KMM 4696. Acruciquinone C is the first member of anthraquinone derivatives with a 6/6/5 backbone. The structures of isolated compounds were established based on NMR and MS data. The absolute stereoconfigurations of new acruciquinones A-C were determined using ECD and quantum chemical calculations (TDDFT approach). A plausible biosynthetic pathway of the novel acruciquinone C was proposed. Compounds 1-4 and 6-13 showed a significant antimicrobial effects against Staphylococcus aureus growth, and acruciquinone A (1), dendryol B (4), coniothyrinone B (7), and ω-hydroxypachybasin (9) reduced the activity of a key staphylococcal enzyme, sortase A. Moreover, the compounds, excluding 4, inhibited urease activity. We studied the effects of anthraquinones 1, 4, 7, and 9 and coniothyrinone D (6) in an in vitro model of skin infection when HaCaT keratinocytes were cocultivated with S. aureus. Anthraquinones significantly reduce the negative impact of S. aureus on the viability, migration, and proliferation of infected HaCaT keratinocytes, and acruciquinone A (1) revealed the most pronounced effect.

Danthron, an Anthraquinone Isolated from a Marine Fungus, Is a New Inhibitor of Angiogenesis Exhibiting Interesting Antitumor and Antioxidant Properties

The role played by a sustained angiogenesis in cancer and other diseases stimulates the interest in the search for new antiangiogenic drugs. In this manuscript, we provide evidence that 1,8- dihydroxy-9,10-anthraquinone (danthron), isolated from the fermentation broth of the marine fungus Chromolaenicola sp. (HL-114-33-R04), is a new inhibitor of angiogenesis. The results obtained with the in vivo CAM assay indicate that danthron is a potent antiangiogenic compound. In vitro studies with human umbilical endothelial cells (HUVEC) reveal that this anthraquinone inhibits certain key functions of activated endothelial cells, including proliferation, proteolytic and invasive capabilities and tube formation. In vitro studies with human breast carcinoma MDA-MB231 and fibrosarcoma HT1080 cell lines suggest a moderate antitumor and antimetastatic activity of this compound. Antioxidant properties of danthron are evidenced by the observation that it reduces the intracellular reactive oxygen species production and increases the amount of intracellular sulfhydryl groups in endothelial and tumor cells. These results support a putative role of danthron as a new antiangiogenic drug with potential application in the treatment and angioprevention of cancer and other angiogenesis-dependent diseases.

A Study of the Metabolic Profiles of Penicillium dimorphosporum KMM 4689 Which Led to Its Re-Identification as Penicillium hispanicum

Changes in cultivation conditions, in particular salinity and temperature, affect the production of secondary fungal metabolites. In this work, the extracts of fungus previously described as Penicillium dimorphosporum cultivated in various salinity and temperature conditions were investigated using HPLC UV/MS techniques, and their DPPH radical scavenging and cytotoxicity activities against human prostate cancer PC-3 cells and rat cardiomyocytes H9c2 were tested. In total, 25 compounds, including 13 desoxyisoaustamide-related alkaloids and eight anthraquinones, were identified in the studied extracts and their relative amounts were estimated. The production of known neuroprotective alkaloids 5, 6 and other brevianamide alkaloids was increased in hypersaline and high-temperature conditions, and this may be an adaptation to extreme conditions. On the other hand, hyposalinity stress may induce the synthesis of unidentified antioxidants with low cytotoxicity that could be very interesting for future investigation. The study of secondary metabolites of the strain KMM 4689 showed that although brevianamide-related alkaloids and anthraquinone pigments are widely distributed in various fungi, these metabolites have not been described for P. dimorphosporum and related species. For this reason, the strain KMM 4689 was re-sequenced using the β-tubulin gene and ITS regions as molecular markers and further identified as P. hispanicum.

Recent advances in the discovery, biosynthesis, and therapeutic potential of isocoumarins derived from fungi: a comprehensive update

Microorganisms still remain the main hotspots in the global drug discovery avenue. In particular, fungi are highly prolific producers of vast structurally diverse specialized secondary metabolites, which have displayed a myriad of biomedical potentials. Intriguingly, isocoumarins is one distinctive class of fungal natural products polyketides, which demonstrated numerous remarkable biological and pharmacological activities. This review article provides a comprehensive state-of-the-art over the period 2000-2022 about the discovery, isolation, classifications, and therapeutic potentials of isocoumarins exclusively reported from fungi. Indeed, a comprehensive list of 351 structurally diverse isocoumarins were documented and classified according to their fungal sources [16 order/28 family/55 genera] where they have been originally discovered along with their reported pharmacological activities wherever applicable. Also, recent insights around their proposed and experimentally proven biosynthetic pathways are also briefly discussed.

Biosynthetic Pathways of Dimeric Natural Products Containing Bisanthraquinone and Related Xanthones

Many dimeric natural products containing bisanthraquinone and related xanthones with diverse structures and versatile bioactivities have been isolated over the years. However, the complicated biosynthetic pathways of such natural products, which have remained elusive until recently, negatively impact their mass bioproduction and biosynthetic structural modification for drug discovery. In this concept, we summarize the recent progress in gene cluster mining and biosynthetic pathway elucidation of natural products containing bisanthraquinone and related xanthones. These pioneering works may pave the way for further biosynthetic pathway elucidation and structure modification of dimeric natural products through gene and protein engineering.

Investigation of the Interaction between Aloe vera Anthraquinone Metabolites and c-Myc and C-Kit G-Quadruplex DNA Structures

G-quadruplexes are nucleotide sequences present in the promoter region of numerous oncogenes, having a key role in the suppression of gene transcription. Recently, the binding of anthraquinones from Aloe vera to G-quadruplex structures has been studied through various physico-chemical techniques. Intrigued by the reported results, we investigated the affinity of aloe emodin, aloe emodin-8-glucoside, and aloin to selected G-quadruplex nucleotide sequences by NMR spectroscopy. The structural determinants for the formation of the ligand/nucleotide complexes were elucidated and a model of the interactions between the tested compounds and C-Kit and c-Myc G-quadruplex DNA structures was built by integrated NMR and molecular modeling studies. Overall, the obtained results confirmed and implemented the previously reported findings, pointing out the complementarity of the different approaches and their contribution to a more detailed overview of the ligand/nucleotide complex formation. Furthermore, the proposed models of interaction could pave the way to the design of new nature-derived compounds endowed with increased G-quadruplex stabilizing activity.