CJ-15,183, a new inhibitor of squalene synthase produced by a fungus, Aspergillus aculeatus

Metabolomic Strategy to Characterize the Profile of Secondary Metabolites in Aspergillus aculeatus DL1011 Regulated by Chemical Epigenetic Agents

Chemical epigenetic regulation (CER) is an effective method to activate the silent pathway of fungal secondary metabolite synthesis. However, conventional methods for CER study are laborious and time-consuming. In the meantime, the overall profile of the secondary metabolites in the fungi treated by the CER reagent is not well characterized. In this study, suberohydroxamic acid (SBHA), a histone deacetylase inhibitor, was added to a culture of Aspergillus aculeatus DL1011 and a new strategy based on LC-MS/MS analysis integrated with various metabolomic tools (MetaboAnalyst, MS-DIAL, SIRIUS and GNPS) was developed to characterize the profile of induced metabolites. As a result, 13.6%, 29.5% and 27.2% of metabolites were identified as newly biosynthesized, increasing and decreasing in abundance by CER, respectively. The structures of the 18 newly induced secondary metabolites were further identified by the new strategy to demonstrate that 72.2% of them (1 novel compound and 12 known compounds) were first discovered in A. aculeatus upon SBHA treatment. The accuracy of the new approach was confirmed by purification and NMR data analysis of major newly biosynthesized secondary metabolites. The bioassay showed that the newly biosynthesized compounds, roseopurpurin analogues, showed selective activities against DPPH scavenging, cytotoxicity and SHP1 inhibition. Our research demonstrated that CER was beneficial for changing the secondary metabolic profile of fungi and was an effective means of increasing the diversity of active metabolites. Our work also supplied a metabolomic strategy to characterize the profile changes and determine the newly induced compounds in the secondary metabolites of fungi treated with the chemical epigenetic regulator.

A new diketopiperazine from an endophytic fungus Aspergillus aculeatus F027

A new diketopiperazine cyclo-(L-Phe-N-ethyl-L-Glu) (1), along with two known diketopiperazines cyclo-(L-Pro-L-Leu) (2) and cyclo-(L-Pro-L-Phe) (3) were isolated from the cultures of an endophytic fungus Aspergillus aculeatus F027. The structures of these compounds were elucidated based on spectroscopic data. The configurations of these compounds were determined by advanced Marfey's analysis. Antibacterial activity of the diketopiperazines against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were also evaluated.Supplemental data for this article can be accessed at https://doi.org/10.1080/14786419.2019.1677652.

Does Osmotic Stress Affect Natural Product Expression in Fungi?

The discovery of new natural products from fungi isolated from the marine environment has increased dramatically over the last few decades, leading to the identification of over 1000 new metabolites. However, most of the reported marine-derived species appear to be terrestrial in origin yet at the same time, facultatively halo- or osmotolerant. An unanswered question regarding the apparent chemical productivity of marine-derived fungi is whether the common practice of fermenting strains in seawater contributes to enhanced secondary metabolism? To answer this question, a terrestrial isolate of Aspergillus aculeatus was fermented in osmotic and saline stress conditions in parallel across multiple sites. The ex-type strain of A. aculeatus was obtained from three different culture collections. Site-to-site variations in metabolite expression were observed, suggesting that subculturing of the same strain and subtle variations in experimental protocols can have pronounced effects upon metabolite expression. Replicated experiments at individual sites indicated that secondary metabolite production was divergent between osmotic and saline treatments. Titers of some metabolites increased or decreased in response to increasing osmolite (salt or glycerol) concentrations. Furthermore, in some cases, the expression of some secondary metabolites in relation to osmotic and saline stress was attributed to specific sources of the ex-type strains.

Asperaculanes A and B, two sesquiterpenoids from the fungus Aspergillus aculeatus

Six sesquiterpenoids 1-6, including two new ones, an ent-daucane-type sesquiterpenoid, asperaculane A (1), and a nordaucane one, asperaculane B (2), and four known nordaucane derivatives, aculenes A-D 3-6, together with the known secalonic acid D (7), were isolated from a fermentation culture of the fungus Aspergillus aculeatus. Their structures and absolute configurations were established by analyses of their spectroscopic data, including 1D and 2D-NMR spectra, HR-ESIMS, electronic circular dichroism (ECD) data, and quantum chemical calculations. These metabolites were evaluated for in vitro cytotoxic activity against two cell lines, human cancer cell lines (HeLa) and one normal hamster cell line (CHO).

Dereplication guided discovery of secondary metabolites of mixed biosynthetic origin from Aspergillus aculeatus

Investigation of the chemical profile of the industrially important black filamentous fungus Aspergillus aculeatus by UHPLC-DAD-HRMS and subsequent dereplication has led to the discovery of several novel compounds. Isolation and extensive 1D and 2D NMR spectroscopic analyses allowed for structural elucidation of a dioxomorpholine, a unique okaramine, an aflavinine and three novel structures of mixed biosynthetic origin, which we have named aculenes A-C. Moreover, known analogues of calbistrins, okaramines and secalonic acids were detected. All novel compounds were tested for antifungal activity against Candida albicans, however all showed only weak or no activity. Aspergillus aculeatus IBT 21030 was additionally shown to be capable of producing sclerotia. Examination of the sclerotia revealed a highly regulated production of metabolites in these morphological structures.

Asperaculin A, a sesquiterpenoid from a marine-derived fungus, Aspergillus aculeatus

A novel sesquiterpenoid, asperaculin A, possessing a novel [5,5,5,6]fenestrane ring system, was isolated from the marine-derived fungus Aspergillus aculeatus CRI323-04. The structure of asperaculin A was established by analysis of spectroscopic data. The name aspergillane is proposed for the sesquiterpene skeleton in asperaculin A.

Antifungal therapy--state of the art at the beginning of the 21st century

The most relevant information on the present state of the art of antifungal chemotherapy is reviewed in this chapter. For dermatomycoses a variety of topical antifungals are available, and safe and efficacious systemic treatment, especially with the fungicidal drug terbinafine, is possible. The duration of treatment can be drastically reduced. Substantial progress in the armamentarium of drugs for invasive fungal infections has been made, and a new class of antifungals, echinocandins, is now in clinical use. The following drugs in oral and/or intravenous formulations are available: the broad spectrum polyene amphotericin B with its new "clothes"; the sterol biosynthesis inhibitors fluconazole, itraconazole, and voriconazole; the glucan synthase inhibitor caspofungin; and the combination partner flucytosine. New therapy schedules have been studied; combination therapy has found a significant place in the treatment of severely compromised patients, and the field of prevention and empiric therapy is fast moving. Guidelines exist nowadays for the treatment of various fungal diseases and maintenance therapy. New approaches interfering with host defenses or pathogenicity of fungal cells are being investigated, and molecular biologists are looking for new targets studying the genomics of pathogenic fungi.

New lipid-modifying therapies

Lipid abnormalities are central among the risk factors for the development of cardiovascular disease and their correction remains a major target for the medical community. Inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A reductase (statins) are the most widely prescribed and best tolerated of the currently available lipid-modifying therapies. Newer agents in this class (e.g., rosuvastatin) have proven to be more effective at lowering levels of low-density lipoprotein cholesterol. New formulations of drugs such as nicotinic acid, which improve treatment regimens and reduce unpleasant side effects, may result in improved patient compliance with this therapy. The development of novel drugs such as cholesterol absorption inhibitors (e.g., ezetimibe) and acyl-coenzyme A cholesterol acyltransferase inhibitors (e.g., avasimibe) will provide clinicians with therapeutic options that exploit different pathways to those currently being utilised. By combining these agents with statins, greater improvements in the lipid profile than those seen to date could be produced. In addition, advances in our understanding of the pathophysiology of dyslipidaemia have enabled other novel therapeutic targets to be identified and studies with experimental drugs underscore the potential of these approaches.