Peptides and polyketides isolated from the marine sponge-derived fungus Aspergillus terreus SCSIO 41008

Terrien, a metabolite made by Aspergillus terreus, has activity against Cryptococcus neoformans

Antimicrobial compounds, including antibiotics, have been a cornerstone of modern medicine being able to both treat infections and prevent infections in at-risk people, including those who are immune-compromised and those undergoing routine surgical procedures. Their intense use, including in people, animals, and plants, has led to an increase in the incidence of resistant bacteria and fungi, resulting in a desperate need for novel antimicrobial compounds with new mechanisms of action. Many antimicrobial compounds in current use originate from microbial sources, such as penicillin from the fungus Penicillium chrysogenum (renamed by some as P. rubens). Through a collaboration with Aotearoa New Zealand Crown Research Institute Manaaki Whenua-Landcare Research we have access to a collection of thousands of fungal cultures known as the International Collection of Microorganisms from Plants (ICMP). The ICMP contains both known and novel species which have not been extensively tested for their antimicrobial activity. Initial screening of ICMP isolates for activity against Escherichia coli and Staphylococcus aureus directed our interest towards ICMP 477, an isolate of the soil-inhabiting fungus, Aspergillus terreus. In our investigation of the secondary metabolites of A. terreus, through extraction, fractionation, and purification, we isolated nine known natural products. We evaluated the biological activity of selected compounds against various bacteria and fungi and discovered that terrein (1) has potent activity against the important human pathogen Cryptococcus neoformans.

Anti-prostate cancer metabolites from the soil-derived Aspergillus neoniveus

Prostate cancer (PCa) ranks as one of the most commonly diagnosed malignancies worldwide. Toxicity, lack of clinical efficacy, and development of resistance phenotypes are the main challenges in the control of prostate malignancies. Notably, castration-resistance prostate cancer (CRPCa) is a highly aggressive and metastatic phenotype of the disease with a poor prognosis and very limited therapeutic options. Herein, we report the isolation and genotypic identification of a soil-derived fungus Aspergillus neoniveus using the PCR-based internal transcribed spacer (ITS) region amplification approach. HPLC/MS investigation of the metabolic profile of the ethyl acetate extract from the fungal biomass revealed tentative identification of forty-five compounds belonging to various chemical classes including γ-butyrolactones, alkaloids, phenolics, and quinoids. Furthermore, the chromatographic purification of microbial extract enabled the identification of nervonic acid methyl ester (1) for the first time from endophytic fungi, as well as acetyl aszonalenin (2), and butyrolactone II (3) for the first time from A. neoniveus. The chemical frameworks of the isolated compounds were identified via extensive spectral analysis including 1 and 2D NMR and MS. The X-ray crystal structure and absolute configuration of acetyl aszonalenin (2) were also determined. Additionally, screening of in vitro anticancer activity of the fungal extract revealed its potential antiproliferative and anti-migratory activities against five different prostate cancer cells (PC3, PC-3M, DU-145, CWR-R1ca, and 22Rv1), including different cells with the castration-resistance phenotype. Moreover, the isolated metabolites significantly inhibited the proliferation, migration, and colonization of human prostate cancer cells at low micromolar levels, thus providing credence for future investigation of these metabolites in relevant anti-prostate cancer animal models. Furthermore, computational target prediction tools identified the cannabinoid G-protein coupled receptors type 1 (CB1) as a potential biological target mediating, at least in part, the anticancer effects of acetylaszonalenin (2). Moreover, molecular modeling and docking studies revealed a favorable binding pose at the CB1 receptor orthosteric ligand pocket aided by multiple polar and hydrophobic interactions with critical amino acids. In conclusion, the Aspergillus neoniveus-derived prenylated indole alkaloid acetylaszonalenin has promising anticancer activity and is amenable to further hit-to-lead optimization for the control of prostate malignancies via modulating CB1 receptors

γ-Aromatic Butenolides of Microbial Source - A Review of Their Structures, Biological Activities and Biosynthesis

γ-Aromatic butenolides (γ-AB) are an important type of structures found in many bioactive microbial secondary metabolites (SMs). γ-AB refer to a group of natural products (NPs) containing five-membered (unsaturated) lactones with 3-phenyl and 4-benzyl substituents. Their wide-range biological activities have inspired pharmaceutical chemists to explore its biosynthesis mechanisms and design strategies to construct the γ-AB skeleton. Recently, there are a great deal of interesting research progress on the structures, biological activities and biosynthesis of γ-AB. This review will focus on these aspects and summarize the important achievements of γ-AB from 1975 to 2021.

Marine Indole Alkaloids-Isolation, Structure and Bioactivities

Indole alkaloids are heterocyclic natural products with extensive pharmacological activities. As an important source of lead compounds, many clinical drugs have been derived from natural indole compounds. Marine indole alkaloids, from unique marine environments with high pressure, high salt and low temperature, exhibit structural diversity with various bioactivities, which attracts the attention of drug researchers. This article is a continuation of the previous two comprehensive reviews and covers the literature on marine indole alkaloids published from 2015 to 2021, with 472 new or structure-revised compounds categorized by sources into marine microorganisms, invertebrates, and plant-derived. The structures and bioactivities demonstrated in this article will benefit the synthesis and pharmacological activity study for marine indole alkaloids on their way to clinical drugs.

Alternariasin A, new pentacyclic cytochalasin from the fungus Alternaria alternate

Alternariasin A (1), one new cytochalasin possessing the benzo[4,5]indeno[2,1-d]isoindole-1,3,13(2H,3aH)-trione skeleton, and five known compounds 2-6 were isolated from the solid cultures of the Midui Glacier-derived fungus Alternaria alternata. Their structures were elucidated by NMR and MS spectroscopic analyses and by a comparison with data from the literature. The absolute configuration of 1 was assigned by combination of experimental and calculated electronic circular dichroism (ECD) spectra. Compound 1 displayed antibacterial activity against the S. aureus, B. subtilis and E. coli with MIC values of 16.7, 16.7 and 33.3 μΜ, respectively. While compound 3 showed potent cytotoxicity against a small panel of human tumour cell lines.

Recent updates on the bioactive compounds of the marine-derived genus Aspergillus

The genus Aspergillus is widely distributed in terrestrial and marine environments. In the marine environment, several Aspergillus species have proved their potential to produce a plethora of secondary metabolites including polyketides, sterols, fatty acids, peptides, alkaloids, terpenoids and miscellaneous compounds, displaying a variety of pharmacological activities such as antimicrobial, cytotoxicity, anti-inflammatory and antioxidant activity. From the beginning of 2015 until December 2020, about 361 secondary metabolites were identified from different marine Aspergillus species. In our review, we highlight secondary metabolites from various marine-derived Aspergillus species reported between January 2015 and December 2020 along with their biological potential and structural aspects whenever applicable.

New Bioactive Sesquiterpeniods From the Plant Endophytic Fungus Pestalotiopsis theae

Three new secondary metabolites pestalothenins A-C (1-3), including two new humulane-derived sesquiterpeniods (1 and 2) and one new caryophyllene-derived sesquiterpeniod (3), together with five known compounds (4-8) were isolated from the crude extract of the plant endophytic fungus Pestalotiopsis theae (N635). Their structures were elucidated by the extensive analyses of HRESIMS and NMR spectroscopic data. The absolute configurations of 1-3 were determined by comparison of experimental and calculated electronic circular dichroism (ECD) spectra. The cytotoxic effects of these compounds were evaluated in vitro. Compound 6 showed moderate cytotoxicity against T24 and MCF7 cell lines. In addition, compounds 1-8 were also evaluated for antibacterial activity.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.

Isolation and Characterization of New Anti-Inflammatory and Antioxidant Components from Deep Marine-Derived Fungus Myrothecium SP. Bzo-l062

In the present study, four new compounds including a pair of 2-benzoyl tetrahydrofuran enantiomers, namely, (−)-1S-myrothecol (1a) and (+)-1R-myrothecol (1b), a methoxy-myrothecol racemate (2), and an azaphilone derivative, myrothin (3), were isolated along with four known compounds (4–7) from cultures of the deep-sea fungus Myrothecium sp. BZO-L062. Enantiomeric compounds 1a and 1b were separated through normal-phase chiral high-performance liquid chromatography. The absolute configurations of 1a, 1b, and 3 were assigned by ECD spectra. Among them, the new compound 1a and its enantiomer 1b exhibited anti-inflammatory activity, inhibited nitric oxide formation in lipopolysaccharide-treated RAW264.7 cells, and exhibited antioxidant activity in the 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) and oxygen radical absorbance capacity assays.

Synthesis and Biological Evaluation of Analogues of Butyrolactone I as PTP1B Inhibitors

In recent years, a large number of pharmacologically active compounds containing a butenolide functional group have been isolated from secondary metabolites of marine microorganisms. Butyrolactone I was found to be produced by Aspergillus terreus isolated from several marine-derived samples. The hypoglycemic activity of butyrolactone I has aroused our great interest. In this study, we synthesized six racemic butenolide derivatives (namely BL-1–BL-6) by modifying the C-4 side chain of butyrolactone I. Among them, BL-3 and BL-5 improved the insulin resistance of HepG2 cells and did not affect the proliferation of RIN-m5f cell line, which indicated the efficacy and safety of BL-3 and BL-5. Furthermore, BL-3, BL-4, BL-5, and BL-6 displayed a significant protein tyrosine phosphatase 1B (PTP1B) inhibitory effect, while the enantiomers of BL-3 displayed different 50% percentage inhibition concentration (IC₅₀) values against PTP1B. The results of molecular docking simulation of the BLs and PTP1B explained the differences of biological consequences observed between the enantiomers of BL-3, which supported BLs as PTP1B inhibitors, and also indicated that the chirality of C-4 might influence the inhibitory effect of the BLs. Our findings provide a novel strategy for the development of butyrolactone derivatives as potential PTP1B inhibitors for the treatment of type 2 diabetes mellitus.

Deep-Sea Fungi Could Be the New Arsenal for Bioactive Molecules

Growing microbial resistance to existing drugs and the search for new natural products of pharmaceutical importance have forced researchers to investigate unexplored environments, such as extreme ecosystems. The deep-sea (>1000 m below water surface) has a variety of extreme environments, such as deep-sea sediments, hydrothermal vents, and deep-sea cold region, which are considered to be new arsenals of natural products. Organisms living in the extreme environments of the deep-sea encounter harsh conditions, such as high salinity, extreme pH, absence of sun light, low temperature and oxygen, high hydrostatic pressure, and low availability of growth nutrients. The production of secondary metabolites is one of the strategies these organisms use to survive in such harsh conditions. Fungi growing in such extreme environments produce unique secondary metabolites for defense and communication, some of which also have clinical significance. Despite being the producer of many important bioactive molecules, deep-sea fungi have not been explored thoroughly. Here, we made a brief review of the structure, biological activity, and distribution of secondary metabolites produced by deep-sea fungi in the last five years.

A Comprehensive Review of Bioactive Peptides from Marine Fungi and Their Biological Significance

Fungal marine microorganisms are a valuable source of bioactive natural products. Fungal secondary metabolites mainly comprise alkaloids, terpenoids, peptides, polyketides, steroids, and lactones. Proteins and peptides from marine fungi show minimal human toxicity and less adverse effects comparable to synthetic drugs. This review summarizes the chemistry and the biological activities of peptides that were isolated and structurally elucidated from marine fungi. Relevant fungal genera including Acremonium, Ascotricha, Aspergillus, Asteromyces, Ceratodictyon, Clonostachys, Emericella, Exserohilum, Microsporum, Metarrhizium, Penicillium, Scytalidium, Simplicillium, Stachylidium, Talaromyces, Trichoderma, as well as Zygosporium were extensively reviewed. About 131 peptides were reported from these 17 genera and their structures were unambiguously determined using 1D and 2D NMR (one and two dimensional nuclear magnetic resonance) techniques in addition to HRMS (high resolution mass spectrometry). Marfey and Mosher reactions were used to confirm the identity of these compounds. About 53% of the isolated peptides exhibited cytotoxic, antimicrobial, and antiviral activity, meanwhile, few of them showed antidiabetic, lipid lowering, and anti-inflammatory activity. However 47% of the isolated peptides showed no activity with respect to the examined biological activity and thus required further in depth biological assessment. In conclusion, when searching for bioactive natural products, it is worth exploring more peptides of fungal origin and assessing their biological activities.