Secondary Metabolites with Agricultural Antagonistic Potential from Aspergillus sp. ITBBc1, a Coral-Associated Marine Fungus.

A marine-derived fungal strain, Aspergillus sp. ITBBc1, was isolated from coral collected from the South China Sea in Hainan province. Intensive chemical investigation of the fermentation extract of this strain afforded four new secondary metabolites (1-4), named megastigmanones A-C and prenylterphenyllin H, along with four known compounds (5-8). Their structures were elucidated by extensive spectroscopic analysis including one-and two-dimensional (1D and 2D) NMR spectroscopy and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The modified Mosher's method was undertaken to determine the absolute configurations of new compounds. The phytotoxic activity test showed that compounds 6-8 exhibited significant antagonistic activity against the germination of Triticum aestivum L. and Oryza sativa L. seeds with a dose-dependent relationship.

COSMO-RS guided screening of ionic liquids for the separation of fluorinated greenhouse gases R-410A: Delving into anion, cation effects, and hydrogen bond dynamics.

Reclamation of high-GWP near-azeotropic refrigerant R-410A (50 wt% R-32 (difluoromethane) + 50 wt% R-125 (pentafluoroethane)) can be an effective way to mitigate the greenhouse effect and achieve a circular economy. Efficient ionic liquids (ILs) as extractants needed to be found for the extractive distillation (ED) separation process of R-410A. Given the numerous combinations of cations and anions in ILs, the discovery of an efficient IL via experimental methods proves to be an exceedingly complex task. In this work, the solubilities of R-32, and R-125 in 840 conventional ILs (comprised of 20 cations and 42 anions) were analyzed based on infinite dilution activity coefficient. The absorption mechanisms of R-32 and R-125 in ILs were elucidated by analyzing excess enthalpy (HE), excess Gibbs free energy (GE)) and surface charge density distribution through COSMO-RS (Conductor-like Screening Model for Real Solvents). Results revealed that HE and GE of the mixture formed by R-125 and most ILs surpassed those of R-32, resulting in higher solubility of R-32 in most ILs compared to R-125. Structural changes of anions and cations had a greater effect on the solubility of R-125 in ILs. It is found for the first time that the existence of a strong hydrogen bond donor region in cations/anions generated intense repulsion with the hydrogen atom in R-125. Furthermore, a large area of weak polarity on the surface of cations/anions was difficult to form an effective charge shield with fluorine atoms in R-125, thus inhibiting the dissolution of R-125. Finally based on the identified interaction sites, combined with melting point and viscosity, some novel functional ILs with high selectivity for R-32 + R-125 were designed and determined for actual separation process. These findings significantly enrich the understanding of the solubility mechanism and provide theoretical guidance for designing new ILs for R-410A reclamation.

Natural Products and Biological Activity from Actinomycetes Associated with Marine Algae.

Marine natural products have been recognized as the most promising source of bioactive substances for drug discovery research. This review illustrates the diversity of culturable actinobacteria associated with marine algae, their bioactivity and metabolites, and approaches to their isolation and determination of their biological properties. Furthermore, actinobacteria associated with marine algae are presented as a new subject for an extensive investigation to find novel and active natural products, which make them a potentially rich and innovative source for new drug development deserving more attention and exploration.

New Isocoumarin and Pyrone Derivatives from the Chinese Mangrove Plant Rhizophora mangle-Associated Fungus Phomopsis sp. DHS-11.

Mangrove-associated fungi are important sources for the discovery of new bioactive natural products. Three new isocoumarins (1-3) and one new pyrone derivative (4) were isolated from the ethyl acetate extract of the fermentation broth of the mangrove endophytic fungus Phomopsis sp. DHS-11. Nuclear magnetic resonance (NMR) spectroscopy (one-dimensional and two-dimensional) and mass spectrometry were used to determine the structures of these new compounds. The absolute configurations for the new isocoumarins 1-3 were determined by comparing their experimental and calculated electronic circular dichroism (ECD) spectra, while the configuration for the new pyrone-derivative 4 was tentatively solved by comparison of its 13C NMR data with reported data. In the biological activity test, compounds 1 and 3 showed cytotoxic activity against HeLa cells with IC50 values of 11.49 ± 1.64 µM and 8.70 ± 0.94 µM, respectively. The initial structure and activity relationship (SAR) analysis revealed that the length of the side chain at C-3 for isocoumarin-type compounds 1-3 could affect the cytotoxicity against HeLa cells. Compound 4 exhibited cytotoxic activities against human hepatoma cells HepG2 with an IC50 value of 34.10 ± 2.92 µM. All compounds have no immunosuppressive activity.

Discovery of p-Terphenyl Metabolites as Potential Phosphodiesterase PDE4D Inhibitors from the Coral-Associated Fungus Aspergillus sp. ITBBc1.

Chemical investigation of the fermentation extract of the coral-associated fungus Aspergillus sp. ITBBc1 led to the discovery of five unreported p-terphenyl derivatives, sanshamycins A-E (1-5), together with five previously described analogues, terphenyllin (6), 3-hydroxyterphenyllin (7), candidusin A (8), 4,5-dimethoxycandidusin A (9), and candidusin C (10). Their structures were elucidated by HRESIMS data and NMR spectroscopic analysis. Compound 1 represents the first example of p-terphenyls with an aldehyde substitution on the benzene ring. Compounds 2-4 feature varying methoxyl and isopentenyl substitutions, while compound 5 features a five-membered lactone linked to a biphenyl. These findings expand the chemical diversity of the family of p-terphenyl natural products. Compounds 1-6 and 9 were evaluated for their inhibitory activity against type 4 phosphodiesterase (PDE4), which is a fascinating drug target for treatment of inflammatory, respiratory, and neurological diseases. Compound 3 was the most potent and exhibited PDE4D inhibitory activity with an IC50 value of 5.543 µM.

Isolation and Identification of Secondary Metabolites Produced by Phytopathogenic Fungus Corynespora cassiicola from Hevea brasiliensis.

The secondary metabolites of the phytopathogenic fungus Corynespora cassiicola CC01 from Hevea brasiliensis were investigated. As a result, two new compounds, 5-acetyl-7-hydroxy-6- methoxybenzofuran-2(3H)-one (1) and (S)-2-(2,3-dihydrofuro [3,2-c]pyridin-2-yl)propan-2-ol (2), together with seven known compounds, 4,6,8-trihydroxy-3,4-dihydronaphthalen-1(2H)-one (3), 3,6,8-trihydroxy-3,4-dihydronaphthalen-1(2H)-one (4), curvulin acid (5), 2-methyl-5-carboxymethyl- 7-hydroxychromone (6), tyrosol (7), p-hydroxybenzoic acid (8) and cerevisterol (9), were isolated from the fermentation extract by comprehensive silica gel, reverse phase silica gel, Sephadex-LH20 column chromatography and high-performance liquid chromatography (HPLC). The structures of these compounds were identified by using high-resolution electrospray mass spectrometry (HRESIMS), nuclear magnetic resonance spectroscopy (NMR), optical rotation, ultraviolet and infrared spectroscopy techniques and a comparison of NMR data with those reported in the literature. Compounds 1 and 2 were new compounds, and compounds 3-9 were discovered from this phytopathogenic fungus for the first time. Compounds 1-9 were tested for phytotoxicity against the fresh tender leaf of Hevea brasiliensis, and the results show that none of them were phytotoxic. Additionally, these compounds were subjected to an antimicrobial assay against three bacteria (E. coli, methicillin-resistant Staphylococcus aureus and Micrococcus luteus), but they showed no activity.

Zhaoshumycins A and B, Two Unprecedented Antimycin-Type Depsipeptides Produced by the Marine-Derived Streptomyces sp. ITBB-ZKa6.

Marine actinomycetes are prolific chemical sources of complex and novel natural products, providing an excellent chance for new drug discovery. The chemical investigation of the marine-derived Streptomyces sp. ITBB-ZKa6, from Zhaoshu island, Hainan, led to the discovery of two unique antimycin-type depsipeptides, zhaoshumycins A (1) and B (2), along with the isolation of the four known neoantimycins A (3), F (4), D (5), and E (6). The structures of the new compounds 1 and 2 were elucidated on the basis of the analysis of diverse spectroscopic data and biogenetic consideration. Zhaoshumycins A (1) and B (2) represent a new class of depsipeptides, featuring two neoantimycin monomers (only neoantimycin D or neoantimycins D and E) linked to a 1,4-disubstituted benzene ring via an imino group. Initial toxicity tests of 1-6 in MCF7 human breast cancer cells revealed that compounds 5 and 6 possess weak cytotoxic activity. Further structure-activity relationship analysis suggested the importance of the NH2 group at C-34 in 5 and 6 for cytotoxicity in MCF7 cells.

Discovery of the leinamycin family of natural products by mining actinobacterial genomes.

Nature's ability to generate diverse natural products from simple building blocks has inspired combinatorial biosynthesis. The knowledge-based approach to combinatorial biosynthesis has allowed the production of designer analogs by rational metabolic pathway engineering. While successful, structural alterations are limited, with designer analogs often produced in compromised titers. The discovery-based approach to combinatorial biosynthesis complements the knowledge-based approach by exploring the vast combinatorial biosynthesis repertoire found in Nature. Here we showcase the discovery-based approach to combinatorial biosynthesis by targeting the domain of unknown function and cysteine lyase domain (DUF-SH) didomain, specific for sulfur incorporation from the leinamycin (LNM) biosynthetic machinery, to discover the LNM family of natural products. By mining bacterial genomes from public databases and the actinomycetes strain collection at The Scripps Research Institute, we discovered 49 potential producers that could be grouped into 18 distinct clades based on phylogenetic analysis of the DUF-SH didomains. Further analysis of the representative genomes from each of the clades identified 28 lnm-type gene clusters. Structural diversities encoded by the LNM-type biosynthetic machineries were predicted based on bioinformatics and confirmed by in vitro characterization of selected adenylation proteins and isolation and structural elucidation of the guangnanmycins and weishanmycins. These findings demonstrate the power of the discovery-based approach to combinatorial biosynthesis for natural product discovery and structural diversity and highlight Nature's rich biosynthetic repertoire. Comparative analysis of the LNM-type biosynthetic machineries provides outstanding opportunities to dissect Nature's biosynthetic strategies and apply these findings to combinatorial biosynthesis for natural product discovery and structural diversity.

Genomic characteristics and comparative genomics analysis of the endophytic fungus Sarocladium brachiariae.

BACKGROUND: Sarocladium brachiariae is a newly identified endophytic fungus isolated from Brachiaria brizantha. A previous study indicated that S. brachiariae had antifungal activity; however, limited genomic information restrains further study. Therefore, we sequenced the genome of S. brachiariae and compared it with the genome of S. oryzae to identify differences between a Sarocladium plant pathogen and an endophyte. RESULTS: In this study, we reported a gapless genome sequence of a newly identified endophytic fungus Sarocladium brachiariae isolated from Brachiaria brizantha. The genome of S. brachiariae is 31.86 Mb, with a contig N50 of 3.27 Mb and 9903 protein coding genes. Phylogenomic analysis based on single copy orthologous genes provided insights into the evolutionary relationships of S. brachiariae and its closest species was identified as S. oryzae. Comparative genomics analysis revealed that S. brachiaria has 14.9% more plant cell wall degradation related CAZymes to S. oryzae, and 33.3% more fungal cell wall degradation related CAZymes, which could explain the antifungal activity of S. brachiaria. Based on Antibiotics & Secondary Metabolite Analysis Shell (antiSMASH) analysis, we identified a contact helvolic acid biosynthetic gene cluster (BGC) for the first time in S. oryzae. However, S. brachiaria had seven fewer terpene gene clusters, including helvolic acid BGC, compared with S. oryzae and this may be associated with adaptation to an endophytic lifestyle. Synteny analysis of polyketide synthases (PKS), non-ribosomal peptide synthetases (NRPS), and hybrid (PKS-NRPS) gene clusters between S. brachiariae and S. oryzae revealed that just 37.5% of tested clusters have good synteny, while 63.5% have no or poor synteny. This indicated that the S. brachiariae could potentially synthesize a variety of unknown-function secondary metabolites, which may play an important role in adaptation to its endophytic lifestyle and antifungal activity. CONCLUSIONS: The data provided a better understanding of the Sarocladium brachiariae genome. Further comparative genomic analysis provided insight into the genomic basis of its endophytic lifestyle and antifungal activity.

A new flavonoid derivative and a new 5-hydroxyanthranilic acid derivative from the sea urchin-derived Streptomyces sp. HDa1.

One new flavonoid derivative flavoside A (1), one new 5-hydroxyanthranilic acid derivative crassilin (2), along with the known angucyclinone PD116740 (3) and oxachelin (4), was isolated from the EtOAc extract of the fermentation broth of the sea urchin (Anthocidaris crassispina)-derived actinobacterium, Streptomyces sp. HD01. The structures of these compounds were established on the basis of their HR-ESI-MS and NMR spectroscopic data. All of these compounds were assessed for their antibacterial activity.

New Eudesmane-Type Sesquiterpenoids from the Mangrove-Derived Endophytic Fungus Penicillium sp. J-54.

Four new eudesmane-type sesquiterpenoids, penicieudesmol A-D (1-4), were isolated from the fermentation broth of the mangrove-derived endophytic fungus Penicillium sp. J-54. Their structures were determined by spectroscopic methods, the in situ dimolybdenum CD method, and modified Mosher's method. The bioassays results showed that 2 exhibited weak cytotoxicity against K-562 cells.

New Antibacterial Phenone Derivatives Asperphenone A-C from Mangrove-Derived Fungus Aspergillus sp. YHZ-1.

Marine fungi are a promising source of novel bioactive natural products with diverse structure. In our search for new bioactive natural products from marine fungi, three new phenone derivatives, asperphenone A-C (1-3), have been isolated from the ethyl acetate extract of the fermentation broth of the mangrove-derived fungus, Aspergillus sp. YHZ-1. The chemical structures of these natural products were elucidated on the basis of mass spectrometry, one- and two-dimensional NMR spectroscopic analysis and asperphenone A and B were confirmed by single-crystal X-ray crystallography. Compounds 1 and 2 exhibited weak antibacterial activity against four Gram-positive bacteria, Staphylococcus aureus CMCC(B) 26003, Streptococcus pyogenes ATCC19615, Bacillus subtilis CICC 10283 and Micrococcus luteus, with the MIC values higher than 32.0 µM.

Anthocidins A⁻D, New 5-Hydroxyanthranilic Acid Related Metabolites from the Sea Urchin-Associated Actinobacterium, Streptomyces sp. HDa1.

Four new 5-hydroxyanthranilic acid related compounds, named anthocidins A⁻D (1⁻4), two known analogues n-lauryl 5-hydroxyanthranilate (5) and isolauryl 5-hydroxyanthranilate (6), together with benzamide (7), 3-hydroxy-4-methoxycinnamamide (8), and (3S-cis)-hexahydro-3-[(3,4-dihydroxyphenyl)methyl]pyrrolo[1,2-a]pyrazine-1,4-dione (9), were isolated from the fermentation broth of the marine-derived actinomycete, Streptomyces sp. HDa1, which was isolated from the gut of a sea urchin, Anthocidaris crassispina, collected from Hainan Island, China. The structures of these secondary metabolites were elucidated on the basis of their 1D and 2D-NMR and mass spectroscopic data, and anthocidin A was confirmed by single-crystal X-ray diffraction with Cu Kα radiation. Anthocidins A⁻D (1⁻4) feature an acetyl group substitution at the amino group and varying alkyl side chains at the carboxyl group of 5-hydroxyanthranilic acid, and compound 5 was isolated as a natural product for the first time. The cytotoxic and antibacterial activity of compounds 1⁻9 were evaluated.

New p-terphenyls from the endophytic fungus Aspergillus sp. YXf3.

Five new p-terphenyls named prenylterphenyllin D (1), prenylterphenyllin E (2), 2'-O-methylprenylterphenyllin (3), 4-O-methylprenylterphenyllin (4) and 3'-O-methylterphenyllin (5) together with seven known compounds (6-12), were isolated from cultures of Aspergillus sp. YXf3. The structures of the new compounds were elucidated by extensive MS and NMR analyses. The NMR and MS data of 5 is reported for the first time, as its structure was listed in SciFinder Scholar with no associated reference. Compounds 6 and 7 were distinguished from each other on the basis of 2D NMR experiments. Compounds 1, 2, 3 and 8 showed antibacterial activities against X. oryzae pv. oryzicola Swings and E. amylovora with the same MIC values of 20µg/mL while 10 exhibited activities against E. amylovora with an MIC value of 10µg/mL.

Metabolites with Insecticidal Activity from Aspergillus fumigatus JRJ111048 Isolated from Mangrove Plant Acrostichum specioum Endemic to Hainan Island.

Fungi residing in mangroves are considered to be a bank of novel bioactive natural products. In the screening for bioactive metabolites from mangrove-derived fungi, the ethyl acetate extract of the fermentation broth of Aspergillus fumigatus JRJ111048, a fungus isolated from the leaves of the mangrove plant Acrostichum specioum endemic to Hainan island, was found to possess insecticidal activity against Spodoptera litura. Bioactivity-guided isolation lead to the discovery of seven metabolites 1-7, including one new anhydride derivative aspergide (1), one new lipid amide 11-methyl-11-hydroxyldodecanoic acid amide (2), and five known compounds; α-ethyl glucoside (3), spiculisporic acid B (4), spiculisporic acid C (5), spiculisporic acid (6), and secospiculisporic acid B (7). Their structures were established by NMR spectroscopic and MS analyses, and by comparison of previously reported data. Insecticidal activity against S. litura and antifungal activity of these compounds were investigated. As a result, the new compound 1 showed potent insecticidal activity against newly hatched larvae of S. litura, and compound 4 displayed weak antifungal activity against Candida albicans.

New Furan Derivatives from a Mangrove-Derived Endophytic Fungus Coriolopsis sp. J5.

Six new furan derivatives, named 5-(3-methoxy-3-oxopropyl)-furan-2-carboxylic acid (1), 1-(5-(2-hydroxypropanoyl)-furan-2-yl)-pentan-3-one (2), 2-hydroxy-1-(5-(1-hydroxypentyl)-furan-2-yl)-propan-1-one (3), 1-(5-(1,2-dihydroxypropyl)-furan-2-yl)-pentan-1-one (4), 5-(1-hydroxypent-4-en-1-yl)-furan-2-carboxylic acid (5) and 5-(3-hydroxypentyl)-furan-2-carboxylic acid (6), together with two new natural products, named 5-(1-hydroxypentyl)-furan-2-carboxylic acid (7) and (E)-5-(2-carboxyvinyl)-furan-2-carboxylic acid (8), were isolated from the solid rice fermentation of endophytic fungus Coriolopsis sp. J5, which was derived from mangrove plant Ceriops tagal. Their structures were unambiguously elucidated based on 1D and 2D NMR spectroscopy, and by HRESIMS measurements, as well as by comparison with the literature.

Atmospheric Chemistry of 1H-Heptafluorocyclopentene (cyc-CF2CF2CF2CF═CH-): Rate Constant, Products, and Mechanism of Gas-Phase Reactions with OH Radicals, IR Absorption Spectrum, Photochemical Ozone Creation Potential, and Global Warming Potential.

The rate constant for gas-phase reactions of OH radicals with 1H-heptafluorocyclopentene (cyc-CF2CF2CF2CF═CH-) was measured using a relative rate method at 298 K: (5.20 ± 0.09) × 10-14 cm3 molecule-1 s-1. The quoted uncertainty includes two standard deviations from the least-squares regression, the systematic error from the GC analysis, and the uncertainties of the rate constants of the reference compounds. The OH-radical-initiated oxidation of cyc-CF2CF2CF2CF═CH- gives the main products COF2, CO, and CO2, leading to negligible environmental impact. For consumptions of cyc-CF2CF2CF2CF═CH- of less than 54%, the yield of the formation of ([COF2] + [CO] + [CO2])/5 (based on the conservation of carbon) was 0.99 ± 0.02, which is very close to 100%. A possible degradation mechanism was proposed. The radiative efficiency (RE) of cyc-CF2CF2CF2CF═CH- measured at room temperature was 0.215 W m-2 ppb-1. The atmospheric lifetime of cyc-CF2CF2CF2CF═CH- was calculated as 0.61 year, and the photochemical ozone creation potential (POCP) was negligible. The 20-, 100-, and 500-year time horizon global warming potentials (GWPs) were estimated as 153, 42, and 12, respectively.

Nematicidal Stemona Alkaloids from Stemona parviflora.

Eight new alkaloids, 3ß-n-butylstemonamine (1), 8-oxo-3ß-n-butylstemonamine (2), 3-n-butylneostemonine (3), 10-epi-3-n-butylneostemonine (4), 8-oxo-oxymaistemonine (5) protostemonine N4-oxide (6), (19S)-hydroxy-21-methoxystemofoline (7), and parvistemonine A (8), were isolated from the roots of Stemona parviflora, together with 17 known alkaloids. The structures of the new alkaloids were elucidated based on a comprehensive spectroscopic data analysis. The absolute configurations of 1-4 were determined by the ECD exciton chirality method and quantum ECD calculations. Protostemonine (10) and stemofoline (12) showed strong nematicidal activity against Panagrellus redivevus, with IC50 values of 0.10 and 0.46 µM, respectively.

Mexicanolide-Type Limonoids from the Roots of Trichilia sinensis.

Four new mexicanolide-type limonoids 1-4, along with two known limonoids 5-6, were isolated from the ethanolic extracts of roots of the Traditional Chinese Medicine Trichilia sinensis. Their structures were unambiguously determined by analysis of spectroscopic data, including 1D and 2D NMR as well as MS, and by comparison with literature data. In addition, the acetylcholinesterase (AChE) inhibitory activity of compounds 1-6 was evaluated by the Ellman method. All these compounds showed weak AChE inhibitory activity, with the inhibition percentages ranging from 18.5% to 27.8%.

Actinotetraose L, a new tetrasaccharide derivative isolated from the mycelia of Amycolatopsis sp. HCa1.

A new tetrasaccharide derivative, actinotetraose L (1), was isolated from the methanol extract of the mycelia of the grasshopper-associated rare actinobacterium Amycolatopsis sp. HCa1. The structure of the new compound was elucidated by a combination of 1D, 2D NMR (HMQC, HMBC, COSY, and NOESY), and HR-ESI-MS analyses as O-{3,4-di-O-[(E)-2-ethyl-2-butenoyl]- ß-D-glucopyranosyl-(1 â†’ 2)}-O-{3,4-di-O-[(E)-2-methyl-2-butenoyl]-ß-D-glucopyranosyl-(1 â†’ 2)}-6,6-di-O-[(E)-2-methyl-2-butenoyl]-α-D-glucopyranosyl-(1 â†’ 1)-α-D-glucopyranoside. The immunosuppressive activity and cytotoxicity of the compound were evaluated by T-cell viability and MTT assays. Nonetheless, no significant activity was observed.