Genomic and Phenotypic Trait Variation of the Opportunistic Human Pathogen Aspergillus flavus and Its Close Relatives

Fungal diseases affect millions of humans annually, yet fungal pathogens remain understudied. The mold Aspergillus flavus can cause both aspergillosis and fungal keratitis infections, but closely related species are not considered clinically relevant. To study the evolution of A. flavus pathogenicity, we examined genomic and phenotypic traits of two strains of A. flavus and three closely related species, Aspergillus arachidicola (two strains), Aspergillus parasiticus (two strains), and Aspergillus nomiae (one strain). We identified >3,000 orthologous proteins unique to A. flavus, including seven biosynthetic gene clusters present in A. flavus strains and absent in the three nonpathogens. We characterized secondary metabolite production for all seven strains under two clinically relevant conditions, temperature and salt concentration. Temperature impacted metabolite production in all species, whereas salinity did not affect production of any species. Strains of the same species produced different metabolites. Growth under stress conditions revealed additional heterogeneity within species. Using the invertebrate fungal disease model Galleria mellonella, we found virulence of strains of the same species varied widely; A. flavus strains were not more virulent than strains of the nonpathogens. In a murine model of fungal keratitis, we observed significantly lower disease severity and corneal thickness for A. arachidicola compared to other species at 48 h postinfection, but not at 72 h. Our work identifies variations in key phenotypic, chemical, and genomic attributes between A. flavus and its nonpathogenic relatives and reveals extensive strain heterogeneity in virulence that does not correspond to the currently established clinical relevance of these species. IMPORTANCE Aspergillus flavus is a filamentous fungus that causes opportunistic human infections, such as aspergillosis and fungal keratitis, but its close relatives are considered nonpathogenic. To begin understanding how this difference in pathogenicity evolved, we characterized variation in infection-relevant genomic, chemical, and phenotypic traits between strains of A. flavus and its relatives. We found extensive variation (or strain heterogeneity) within the pathogenic A. flavus as well as within its close relatives, suggesting that strain-level differences may play a major role in the ability of these fungi to cause disease. Surprisingly, we also found that the virulence of strains from species not considered to be pathogens was similar to that of A. flavus in both invertebrate and murine models of disease. These results contrast with previous studies on Aspergillus fumigatus, another major pathogen in the genus, for which significant differences in infection-relevant chemical and phenotypic traits are observed between closely related pathogenic and nonpathogenic species.

Marine Sponge-Associated Fungi as Potential Novel Bioactive Natural Product Sources for Drug Discovery: A Review

Marine sponge-associated fungi are promising sources of structurally interesting and bioactive secondary metabolites. Great plenty of natural products have been discovered from spongeassociated fungi in recent years. Here reviewed are 571 new compounds isolated from marine fungi associated with sponges in 2010-2018. These molecules comprised eight different structural classes, including alkaloids, polyketides, terpenoids, meroterpenoids, etc. Moreover, most of these compounds demonstrated profoundly biological activities, such as antimicrobial, antiviral, cytotoxic, etc. This review systematically summarized the structural diversity, biological function, and future potential of these novel bioactive natural products for drug discovery.

Marine-Derived Macrolides 1990-2020: An Overview of Chemical and Biological Diversity

Macrolides are a significant family of natural products with diverse structures and bioactivities. Considerable effort has been made in recent decades to isolate additional macrolides and characterize their chemical and bioactive properties. The majority of macrolides are obtained from marine organisms, including sponges, marine microorganisms and zooplankton, cnidarians, mollusks, red algae, bryozoans, and tunicates. Sponges, fungi and dinoflagellates are the main producers of macrolides. Marine macrolides possess a wide range of bioactive properties including cytotoxic, antibacterial, antifungal, antimitotic, antiviral, and other activities. Cytotoxicity is their most significant property, highlighting that marine macrolides still encompass many potential antitumor drug leads. This extensive review details the chemical and biological diversity of 505 macrolides derived from marine organisms which have been reported from 1990 to 2020.

Procerolides A-B from Microcionidae marine sponge Clathria procera: Anti-inflammatory macrocylic lactones with selective cyclooxygenase-2 attenuation properties

Cyclooxygenase-2 has been recognized to catalyze the formation of inflammatory prostaglandins from arachidonic acid. Attenuation potential against cyclooxygenase-2 coupled with greater anti-inflammatory selectivity index were contemplated to be vital indicators to assess anti-inflammatory activities of bioactive compounds. In the present study, two undescribed fourteen-membered macrocyclic lactones, procerolide A and B were isolated to homogeneity from the organic extract of the marine sponge Clathria procera (family: Microcionidae). Procerolide B exhibited greater attenuation potential against cyclooxygenase-2 (IC₅₀ 0.89 mM) than that displayed by procerolide A, whereas 5-lipoxygenase inhibitory activity of procerolide B (IC₅₀ 1.08 mM) was significantly greater than that displayed by procerolide A (IC₅₀ 0.95 mM) and anti-inflammatory agent ibuprofen (IC₅₀ 4.50 mM). Additionally, greater anti-inflammatory selectivity index of the procerolides (~1.3) than the synthetic agent (0.43) was accounted for the selective inhibition of the compounds towards cyclooxygenase-2. Higher electronic properties (topological polar surface area of > 100) along with lesser steric properties (molar volume < 300 cm³) of the compounds compared to the standard supported their significant anti-inflammatory potential. Additionally, procerolide B exhibited comparatively lesser binding energy with aminoacyl residues of cyclooxygenase-2 (-9.82 kcal/mol) thereby recognizing its prospective therapeutic use against inflammatory pathogenesis.

Total synthesis: the structural confirmation of natural products

This feature article highlights total synthesis as one of the reliable tools for the structural confirmation of natural products.

Biological and Chemical Diversity of Marine Sponge-Derived Microorganisms over the Last Two Decades from 1998 to 2017

Marine sponges are well known as rich sources of biologically natural products. Growing evidence indicates that sponges harbor a wealth of microorganisms in their bodies, which are likely to be the true producers of bioactive secondary metabolites. In order to promote the study of natural product chemistry and explore the relationship between microorganisms and their sponge hosts, in this review, we give a comprehensive overview of the structures, sources, and activities of the 774 new marine natural products from sponge-derived microorganisms described over the last two decades from 1998 to 2017.

Synthesis of chiral propargyl alcohols following the base-induced elimination protocol: application in the total synthesis of natural products

Synthesis of enantiomerically pure propargyl alcohols is one of the most important tools in organic synthesis and “base-induced elimination of β-alkoxy chlorides” could offer the enantiomerically pure propargyl alcohols.

Four New C9 Metabolites from the Sponge-Associated Fungus Gliomastix sp. ZSDS1-F7-2

Four new structurally related metabolites, one γ-lactone named gliomasolide F (1), one δ-lactone named gliomasolide G (2), and two medium-chain fatty acids named gliomacids A–B (3–4), each containing nine carbons in total, were identified from the sponge-associated fungus Gliomastix sp. ZSDS1-F7-2. The planar chemical structures of these novel C9 metabolites were elucidated by nuclear magnetic resonance (NMR) spectroscopic methods, in connection with the analysis of high-resolution mass spectrometry (HRMS) and infrared (IR) data. The absolute configuration of 1, was determined by comparisons of experimental circular dichroism (CD) and optical rotation (OR) value with corresponding ones computed by quantum chemistry. The relative configuration of 2 was determined by the Nuclear Overhauser effect spectroscopy (NOESY) spectrum, while its absolute configuration was tentatively determined in view of the biogenetic and biosynthetic relationships between 1 and 2. Compounds 3–4, originally as an inseparable mixture, were successfully isolated after chemical modifications. The stereo-chemistries of compounds 3–4 were assumed by comparison of ¹³C NMR with those of the similar moiety reported in literature, in addition to the biogenetic and biosynthetic relationships with 1. The plausible biosynthetic relationships among these four C9 metabolites were supposed. Biologically, compounds 1–4 showed no cytotoxic effect against HeLa cell line at concentrations up to 25 μg/mL, while 1 exhibited moderate antifouling activity against the settlement of Balanus amphitrite larvae with IC₅₀ being 12.8 μg/mL and LC₅₀ > 25 μg/mL. The co-occurrence of macrolides gliomasolides A—E and four C9 metabolites in the same fermentation culture made us assume that these C9 metabolites might be biosynthetic building blocks toward the construction of more complex macrolides such as gliomasolides A—E or other unidentified polyketides.

Natural Products Research in China From 2015 to 2016

This review covers the literature published by chemists from China during the 2015-2016 on natural products (NPs), with 1,985 citations referring to 6,944 new compounds isolated from marine or terrestrial microorganisms, plants, and animals. The emphasis is on 730 new compounds with a novel skeleton or/and significant bioactivity, together with their source organism and country of origin.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) 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 (1340 in 429 papers for 2015), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Determination of the Absolute Configuration of Gliomasolide D through Total Syntheses of the C-17 Epimers

The absolute configuration at C-17, the carbon bearing the distal hydroxy group of the 14-membered natural product gliomasolide D, was assigned as R by comparison of ¹³C NMR shifts and specific rotation values of the epimers at C-17. The first total synthesis of gliomasolide D along with its C-17 epimer, regioselective macrocyclization (18 membered vs 14 membered), and regioselective Wacker oxidation are highlights of the present work.

Hydroquinone derivatives from the marine-derived fungus Gliomastix sp

A novel cytotoxic quinone/hydroquinone dimer from the marine-derived fungus Gliomastix sp.

Modular Synthesis of Novel Macrocycles Bearing α,β-Unsaturated Chemotypes through a Series of One-Pot, Sequential Protocols

A series of one-pot, sequential protocols was developed for the synthesis of novel macrocycles bearing α,β-unsaturated chemotypes. The method highlights a phosphate tether-mediated approach to establish asymmetry, and consecutive one-pot, sequential processes to access the macrocycles with minimal purification procedures. This library amenable strategy provided diverse macrocycles containing α,β-unsaturated carbon-, sulfur-, or phosphorus-based warheads.

A Pot-Economical Approach to the Total Synthesis of Sch-725674

A pot-economical total synthesis of antifungal Sch-725674, 1, is reported. The approach takes advantage of a number of one-pot, sequential transformations, including a phosphate tether-mediated one-pot, sequential RCM/CM/chemoselective hydrogenation protocol, a one-pot tosylation/acrylation sequence, and a one-pot, sequential Finkelstein reaction/Boord olefination/acetonide deprotection procedure to streamline the synthesis route by reducing isolation and purification procedures, thus saving time. Overall, an asymmetric route has been developed that is efficiently accomplished in seven pots from phosphate (S,S)-triene and with minimal purification.