Characterizing the Influence of a Heterotrophic Bicosoecid Flagellate Pseudobodo sp. on the Dinoflagellate Gambierdiscus balechii.

Microbial interactions including competition, mutualism, commensalism, parasitism, and predation, which can be triggered by nutrient acquisition and chemical communication, are universal phenomena in the marine ecosystem. The interactions may influence the microbial population density, metabolism, and even their environmental functions. Herein, we investigated the interaction between a heterotrophic bicosoecid flagellate, Pseudobodo sp. (Bicoecea), and a dinoflagellate, Gambierdiscus balechii (Dinophyceae), which is a well-known ciguatera food poisoning (CFP) culprit. The presence of Pseudobodo sp. inhibited the algal proliferation and decreased the cardiotoxicity of zebrafish in the algal extract exposure experiment. Moreover, a significant difference in microbiome abundance was observed in algal cultures with and without Pseudobodo sp. Chemical analysis targeting toxins was performed by using liquid chromatography-tandem mass spectrometry (LC-MS/MS) combined with molecular networking (MN), showing a significant alteration in the cellular production of gambierone analogs and some super-carbon chain compounds. Taken together, our results demonstrated the impact of heterotrophic flagellate on the photosynthetic dinoflagellates, revealing the complex dynamics of algal toxin production and the ecological relationships related to dinoflagellates in the marine environment.

Kueishanamides A and B from the Hydrothermal Vent Sediment Derived Streptomyces sp. WU20.

Marine actinomycetes are known for their production of remarkable organic molecules, particularly those featuring polyoxygenated long-chain backbones. Determining the absolute configurations of these compounds remains a challenging task even today. In this study, we successfully established the planar structures and absolute configurations of two highly flexible amide alkaloids from Streptomyces sp. WU20: kueishanamides A (1) and B (2). These compounds possess a C13 linear backbone and each contains five stereogenic carbon centers. Our approach involved a combination of spectroscopic and computational methods, including J-based configurational analysis and VCD calculations, ensuring the unambiguous determination of their configurations. Kueishanamide A (1) and kueishanamide B (2) showed moderate antifungal activity against pathogenic fungus Crytococcus neoformans, with MIC values of 25 µg/mL each.

Chemistry and bioactivities of alkaloids isolated from marine fungi (covering 2016-2022).

The ocean is a treasure house with rich resources of new chemical and biological molecules. A growing body of evidence suggests that marine fungi represent a huge and largely untapped resource of natural products that have been optimized by evolution for biological and ecological relevance. Alkaloids, the important components of natural products, have attracted much attention from medicinal and natural product chemists due to their unique structures and biological potential. The number and variety of alkaloids from marine fungi discovered in recent years maintain an upward trend. This review would give a systematic overview of the structures and bioactivities of marine fungal alkaloids obtained over the past six years and inspire the development of novel pharmaceutical agents.

Cytotoxic shornephines and asterresins from the hydrothermal vent associated fungus Aspergillus terreus CXX-158-20.

A previously unreported alkaloid, bearing an undescribed 5/7/8 tricyclic heterocyclic skeleton, shornephine D, an undescribed diketomorpholine (DKM) shornephine B, two undescribed diketomorpholine derivatives shornephine C and seco-shornephine B methyl ester, an undescribed indole-isoquinoline alkaloid asterresin C, three undescribed indole alkaloids asterresins A-B and D, together with five known compounds, were isolated from the culture of hydrothermal vent associated fungus Aspergillus terreus CXX-158-20. Their structures were unambiguously determined by nuclear magnetic resonance (NMR), mass spectrometry, Mosher's method, 13C NMR calculation in combination with DP4+, and ECD calculations. Shornephine D and asterresin C represent two undescribed heterocyclic skeletons. Asterresin D and giluterrin exhibited cytotoxicity activities with IC50 values of 3.96 µM and 7.97 µM against A549 cell line. Asterresin D exhibited cytotoxicity activities with IC50 values of 12.36 µM and 12.48 µM against Namalwa and U266 cell lines. Asterresin A and giluterrin exhibited synergistic effect with adriamycin against MCF-7 cell line.

Structures and bioactivities of secondary metabolites from Penicillium genus since 2010.

Penicillium genus was a fungal endophyte first reported by Alexander Fleming in 1928 and attracted more attention in recent decades due to its multitudinous metabolites which possess novel skeletons, abundant bioactivities and potential in medicine. Up to now, >300 Penicillium species were found all around the world. The review summarized secondary metabolites derived from the Penicillium genus since 2010, including their chemical structures and biological activities.

Citrinin Monomer, Trimer, and Tetracyclic Alkaloid Derivatives from the Hydrothermal Vent-Associated Fungus Penicillium citrinum TW132-59.

Five new unusual citrinin-derived alkaloids with a tetracyclic core, citrinidines A-E (1-5), two new amide alkaloids, methyl (2S,8E)-1'-(2-methyl-3-oxodec-8-enamido) butanoate (6) and (2S,8E)-2-methyl-3-oxodec-8-enamide (7), a new unusual citrinin trimer, tricitrinol C (8), a new citrinin acetal-ketal derivative, citrininol (9), together with four known citrinin monomers (10-13), and three known citrinin dimers (14-16), were isolated from the fermentation of hydrothermal vent-associated fungus Penicillium citrinum TW132-59. Their structures were unambiguously determined by nuclear magnetic resonance (NMR), mass spectrometry, Mosher's method, 13C NMR calculation in combination with DP4+, and ECD calculations. A plausible biosynthetic pathway of all new compounds (1-9) was proposed. Citrinin trimer (8) exhibited potent cytotoxicity activity with an IC50 value of 1.34 ± 0.11 µM, and compounds 1 and 15 showed moderate cytotoxicity with IC50 values of 17.50 ± 1.43 and 9.45 ± 0.55 µM, respectively, against A549 cell line.

New Cytotoxic Secondary Metabolites from Two Deep-Sea-Derived Fungi and the Co-Culture Impact on the Secondary Metabolic Patterns.

In this study, chemical profiles for two co-existing deep-sea-derived Penicillium fungal strains were thoroughly investigated. Two new compounds and 11 known compounds were identified from Penicillium sp. LXY140-R, while one new compound and 12 known compounds were isolated from Penicillium sp. LXY140-3. Their structures were elucidated by extensive 1D and 2D NMR experiments, which were supported by HR-ESI-MS data. The antiproliferative activities of all isolates against HCT-116, A549 and Bel-7402 cell lines were also evaluated. Compounds 2, 5, 6, 10 and 13 showed potent antiproliferative activity. To reveal the metabolic relationship of the two strains, we conducted co-culture experiments to discover cross-talk molecules by a device that allows only small molecule to communicate. Extensive HPLC/MS2 experiments were applied to identify the disturbance of the chemical profiles within the synthetic Penicillium-Penicillium community. The fungal strain LXY140-R was found to accumulate mono or multiple-acetylation derivatives of deoxynivalenol (DON) sesquiterpenes as responsible molecules by the disturbance of the metabolites produced by the LXY140-3 strain.

Characterization of New Gambierones Produced by Gambierdiscus balechii 1123M1M10.

The benthic dinoflagellate genus Gambierdiscus is the primary producer of toxins responsible for ciguatera poisoning (CP), a food intoxication endemic in tropical and subtropical areas of the world. We used high-performance liquid chromatography tandem high-resolution mass spectrometry (HPLC-HRMS) to investigate the toxin profile of Gambierdiscus balechii 1123M1M10, which was obtained from Marakei Island (2°01'N, 173°15'E), Republic of Kiribati, located in the central Pacific Ocean. Four new gambierone analogues including 12,13-dihydro-44-methylgambierone, 38-dehydroxy-12,13-dihydro-44-methylgambierone, 38-dehydroxy-44-methylgambierone, and desulfo-hydroxyl gambierone, and two known compounds, gambierone and 44-methylgambierone, were proposed by analyzing their fragmentation behaviors and pathways. Our findings provide new insights into the toxin profile of Gambierdiscus balechii 1123M1M10, which can be used as a biomarker for species identification, and lay the foundation for further toxin isolation and bioactivity studies of gambierones.