New Butenolides and Cyclopentenones from Saline Soil-Derived Fungus Aspergillus Sclerotiorum

Alkaloid diversity expansion of a talent fungus Penicillium raistrichii through OSMAC-based cultivation

Introduction

Alkaloidal natural products are attractive for their broad spectrum of pharmaceutical bioactivities. In the present work, the highly productive saline soil derived fungus, Penicillium raistrichii, was subjected to the strategy of OSMAC (one strain many compounds) with changes of cultivation status. Then, the work-flow led to the expansion of the alkaloid chemical diversity and subsequently induced the accumulation of four undescribed alkaloids, named raistrimides A-D (1-4), including three β-carbolines (1-3), one 2-quinolinone (4), and one new natural product, 2-quinolinone (5), along with five known alkaloid chemicals (6-10).

Methods

A set of NMR techniques including 1H, 13C, HSQC and HMBC, along with other spectroscopic data of UV-Vis, IR and HRESIMS, were introduced to assign the plain structures of compounds 1-10. The absolute configuration of 1-3 were elucidated by means of X-ray crystallography or spectroscopic analyses on optical rotation values and experimental electronic circular dichroism (ECD) data. In addition, it was the first report on the confirmation of structures of 6, 7 and 9 by X-ray crystallography data. The micro-broth dilution method was applied to evaluate antimicrobial effect of all compounds towards Staphylococcus aureus, Escherichia coli, and Candida albicans.

Results and discussion

The results indicated compounds 1, 3 and 4 to be bioactive, which may be potential for further development of anti-antimicrobial agents. The finding in this work implied that OSMAC strategy was a powerful and effective tool for promotion of new chemical entities from P. raistrichii.

The Novel Compounds with Biological Activity Derived from Soil Fungi in the Past Decade

The secondary metabolites isolated from soil fungi have received more and more attention, especially new compounds that exhibited good biological activities. In this review, a total of 546 new compounds are included in the relevant literature since 2011. The new compounds are isolated from soil fungi, We divided these compounds into seven categories, including alkaloids, terpenoids, steroids, ketones, phenylpropanoids, quinones, esters, lactones, etc. In addition, the biological activities and structure-activity relationships of these compounds have also been fully discussed. The activities of these compounds are roughly divided into eight categories, including anticancer activity, antimicrobial activity, anti-inflammatory activity, antioxidant activity, antiviral activity, antimalarial activity, immunosuppressive activity and other activities. Since natural products are an important source of new drugs, this review may have a positive guiding effect on drug screening.

Natural Enantiomers: Occurrence, Biogenesis and Biological Properties

The knowledge that natural products (NPs) are potent and selective modulators of important biomacromolecules (e.g., DNA and proteins) has inspired some of the world’s most successful pharmaceuticals and agrochemicals. Notwithstanding these successes and despite a growing number of reports on naturally occurring pairs of enantiomers, this area of NP science still remains largely unexplored, consistent with the adage “If you don’t seek, you don’t find”. Statistically, a rapidly growing number of enantiomeric NPs have been reported in the last several years. The current review provides a comprehensive overview of recent records on natural enantiomers, with the aim of advancing awareness and providing a better understanding of the chemical diversity and biogenetic context, as well as the biological properties and therapeutic (drug discovery) potential, of enantiomeric NPs.

α-Glucosidase and PTP-1B Inhibitors from Malbranchea dendritica

An extract from a PDB static culture of Malbranchea dendritica exhibited α-glucosidase and PTP-1B inhibitory activities. Fractionation of the active extract led to the isolation of gymnoascolide A (1), a γ-butenolide, and xanthones sydowinin A (2), sydowinin B (3), and AGI-B4 (4), as well as orcinol (5). Compound 1 exhibited important inhibitory activity against yeast α-glucosidase (IC₅₀ = 0.556 ± 0.009 mM) in comparison to acarbose (IC₅₀ = 0.403 ± 0.010 mM). Kinetic analysis revealed that 1 is a mixed-type inhibitor. Furthermore, compound 1 significantly reduced the postprandial peak in mice during a sucrose tolerance test at the doses of 5.16 and 10 mg/kg. Compound 1 was reduced with Pd/C to yield a mixture of enantiomers 1a and 1b; the mixture showed similar activity against α-glucosidase (IC₅₀ = 0.396 ± 0.003 mM) and kinetic behavior as the parent compound but might possess better drug-likeness properties according to SwissADME and Osiris Property Explorer tools. Docking analysis with yeast α-glucosidase (pdb: 3A4A) and the C-terminal subunit of human maltase-glucoamylase (pdb: 3TOP) predicted that 1, 1a, and 1b bind to an allosteric site of the enzymes. Compounds 1-5 were evaluated against PTP-1B, but only xanthone 3 moderately inhibited in a noncompetitive fashion the enzyme with an IC₅₀ of 0.081 ± 0.004 mM. This result was consistent with that of docking analysis, which revealed that 3 might bind to an allosteric site of the enzyme. From the inactive barley-based semisolid culture of M. dendritica, the natural pigment erythroglaucin (6) and the nucleosides deoxyadenosine (7), adenosine (8), thymidine (9), and uridine (10) were also isolated and identified.

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.

Penicillic Acid Congener, a New Inhibitor of BMP-Induced Alkaline Phosphatase Activity in Myoblasts, Produced by the Fungus Penicillium sp. BF-0343

During our screening for microbial regulators of bone metabolism, a new compound, 6-ethoxy-5,6-dihydropenillic acid (1), was isolated together with a known and structurally related penicillic acid (2) from the culture broth of the soil-derived fungus Penicillium sp. BF-0343. The structure of 1 was elucidated by various spectroscopic data including nuclear magnetic resonance experiments. Compounds 1 and 2 dose-dependently inhibited bone morphogenetic protein–induced alkaline phosphatase activity in myoblasts with half-maximal inhibitory concentration values of 19.8 and 2.1 μM, respectively.