Genomics-driven discovery of a new cyclodepsipeptide from the guanophilic fungus Amphichorda guana.

Two potential non-ribosomal peptide synthetases (NRPSs) were identified in the genome of a guanophilic fungus Amphichorda guana by bioinformatics analysis and gene knockout experiments. Liquid chromatography coupled with mass spectrometry (LC-MS) guided isolation led to the discovery of a new cyclodepsipeptide isaridin H (1) and seven known analogs, desmethylisaridin E (2), isaridin E (3), isariin A (4), iso-isariin B (5), iso-isariin D (6), isariin E (7), and nodupetide (8). The absolute configuration of isaridin H (1) was achieved by Marfey's method. Isaridin H (1) showed significant antifungal activity against Botrytis cinerea and Alternaria solani.

Genetic dereplication driven discovery of a tricinoloniol acid biosynthetic pathway in Trichoderma hypoxylon.

A genetic dereplication approach in combination with differential gene expression led to the discovery of three new sesquiterpenes, tricinoloniol acids (TRAs) A-C (1-3) and the known fusidilactone A (4) from T. hypoxylon. Comparative transcriptomic analysis and targeted deletion identified the biosynthetic route for TRAs. Our results demonstrate an alternative application of the genetic dereplication method for exploring the biosynthesis of cryptic secondary metabolites (SMs), which utilizes the coordinated expression of trichothecene (tri) and tra cluster genes.

Cytotoxic, Anti-Migration, and Anti-Invasion Activities on Breast Cancer Cells of Angucycline Glycosides Isolated from a Marine-Derived Streptomyces sp.

Four angucycline glycosides were previously characterized from marine-derived Streptomyces sp. OC1610.4. Further investigation of this strain cultured on different fermentation media from that used previously resulted in the isolation of two new angucycline glycosides, vineomycins E and F (1-2), and five known homologues, grincamycin L (3), vineomycinone B2 (4), fridamycin D (5), moromycin B (7), and saquayamycin B1 (8). Vineomycin F (2) contains an unusual ring-cleavage deoxy sugar. All the angucycline glycosides isolated from Streptomyces sp. OC1610.4 were evaluated for their cytotoxic activity against breast cancer cells MCF-7, MDA-MB-231, and BT-474. Moromycin B (7), saquayamycin B1 (8), and saquayamycin B (9) displayed potent anti-proliferation against the tested cell lines, with IC50 values ranging from 0.16 to 0.67 µM. Saquayamycin B (9) inhibited the migration and invasion of MDA-MB-231 cells in a dose-dependent manner, as detected by Transwell and wound-healing assays.

Characterization and mechanism of anti-Aeromonas salmonicida activity of a marine probiotic strain, Bacillus velezensis V4.

The bacterium Aeromonas salmonicida is the causative agent of furunculosis, a systemic, ubiquitous disease of fish in the salmon family, characterized by high mortality and morbidity. Probiotics are a promising approach for prevention of furunculosis in aquaculture. A bacterial strain with anti-A. salmonicida properties, Bacillus velezensis V4, was isolated and the mechanisms underlying these properties were investigated. Anti-A. salmonicida compounds present in cell-free supernatant of V4 were purified and structurally identified as members of the iturin, macrolactin, and difficidin groups. The compounds contributed jointly to inhibition of A. salmonicida, and the diversity of the compounds was related to the versatility of their mode of action. Addition of the compounds to A. salmonicida cell suspensions reduced cell density. Analyses by confocal microscopy and scanning electron microscopy revealed cell membrane disruption, deletion of cellular content, and cell lysis of A. salmonicida. The V4 genome was sequenced, and gene clusters involved in synthesis of anti-Aeromonas compounds were detected and identified. A possible probiotic effect on growth performance of Oncorhynchus mykiss (rainbow trout) was investigated by addition of 0, 1, and 3 % (v/w) V4. Relative to control, mortality was reduced 27.25 % in the 1 % addition group and 81.86 % in the 3 % addition group. Feed coefficient ratio was reduced 19.49 % and weight gain ratio was increased 71.22 % in the 1 % addition group. Our findings demonstrate that V4 is an effective probiotic strain in O. mykiss and has clear potential for both control of furunculosis and growth promotion of aquaculture animals.

Depside α-glucosidase inhibitors from a culture of the mushroom Stereum hirsutum.

Nine new isoprenylated depsides, sterenins E-M (1-9), as well as five known compounds (10-14), were isolated from the solid culture of Stereum hirsutum. The structures of the new compounds were elucidated by spectroscopic methods. Their inhibitory activities against yeast α-glucosidase were evaluated in vitro. Compounds 1-4 and 7-14 showed inhibitory activities with IC50 values of 7.62, 3.06, 6.03, 22.70, 36.64, 13.09, 27.52, 25.10, 12.32, 3.31, 23.82, and 14.17 µM, respectively. Compounds 5 and 6 showed no inhibitory activities with IC50 values higher than 50 µM. Therefore, the culture of S. hirsutum and its secondary metabolites could have a potential usage for the development of hypoglycemic drugs.

Caesalpinbondin A, a Novel Diterpenoid Lactone With an Unprecedented Carbon Skeleton from the Seeds of Caesalpinia bonduc.

One novel diterpenoid lactone named caesalpinbondin A (1) that possesses an unprecedented tetracyclic ring system in which a 6/6/5-fused tricyclic ring and a 4,5-dimethyldihydrofuran-2(3H)-one were connected by a C-C single bond comprising a 5-(naphtho [2,3-b]furan-7-yl)dihydrofuran-2(3H)-one moiety was isolated from the seeds of Caesalpinia bonduc. Its chemical structure was established by extensive spectroscopic methods, and its absolute configuration was further determined by single-crystal X-ray diffraction analysis and electronic circular dichroism calculation. The biological evaluation suggested that compound 1 demonstrated potent anti-Alzheimer's disease (AD) bioactivity, which could delay paralysis of transgenic AD Caenorhabditis elegans. A possible biogenetic pathway of 1 was also proposed.

Diterpenoids and C13 Nor-Isoprenoid Identified From the Leaves and Twigs of Croton yanhuii Activating Apoptosis and Pyroptosis.

Croton yanhuii (Family Euphorbiaceae) is an annual aromatic plant endemic to Yunnan Province, China, which yields an aromatic, spicy oil used as a flavoring and fragrance. The aim of the present study was to acquire secondary metabolites from the leaves and twigs of C. yanhuii and to evaluate their cytotoxic activity. Five new diterpenoids, croyanhuins A-E (1-5), and one new C13 nor-isoprenoid, croyanhuin F (6), were isolated from the leaves and twigs of C. yanhuii. Their structures and absolute configurations were determined by extensive spectroscopic methods (1D and 2D NMR, IR, and HRESIMS) and confirmed by electronic circular dichroism (ECD) spectra or single-crystal X-ray diffraction analysis. Among the new terpenoids, compounds 1 and 3 inhibited cell proliferation and viability in a dose- and time-dependent manner, whereas both induced cleavage of either caspase-3 or PARP-1 in the SW480 cell line. Additionally, we observed that Z-YVAD-FMK and Z-VAD-FMK, two caspase inhibitors, inhibited the compound-dependent cell viability loss, suggesting that either of them can induce pyroptosis and caspase-dependent apoptosis. These biological assay results revealed that compounds 1 and 3 induce different kinds of programmed cell death in SW480 cells.

p-Terphenyls and actinomycins from a Streptomyces sp. associated with the larva of mud dauber wasp.

In the course of searching for cytotoxic metabolites from insects associated actinomyces, two new natural p-terphenyl glycosides, strepantibin D (1) and strepantibin E (2), along with terferol (3), actinomycin D (4), actinomycin V (5) and actinomycin V0ß (6), were identified from the fermentation medium of a Streptomyces sp. which was obtained from the larva body of mud dauber wasp. Strepantibin D (1), previously reported as a synthetic derivative of terfestatin A, is firstly isolated as a natural p-terphenyl in this research. Strepantibin D (1) and terferol (3) showed medium cytotoxic activity against breast cancer cells MCF-7, MDA-MB-231 and BT-474. Actinomycins (4-6), especially actinomycin V (5), displayed remarkable cytotoxicity against breast cancer cells, with IC50 values ranging from 0.83 nM to 369.90 nM.

Labdane diterpenoid glycosides from Aster veitchianus.

Four new labdane-type rhamnopyranosides derived from 13-epimanool, compounds 1-4, with differently acetylated sugar moieties, were isolated from A. veitchianus. Their structures and absolute configurations were elucidated by chemical transformation, spectroscopic and mass-spectrometric analyses (IR, 1D- and 2D-NMR, HR-ESI-MS), as well as by single-crystal X-ray diffraction (compound 1). The isolates 2-4 were investigated for their cytotoxic properties against cultured human hepatoma (SMMC-7721), ovarian neoplasm (HO-8910), and leukemia (HL-60) cells, and for their antibacterial activities against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus.

Mechanism of anti-Vibrio activity of marine probiotic strain Bacillus pumilus H2, and characterization of the active substance.

Vibriosis is a major epizootic disease that impacts free-living and farmed fish species worldwide. Use of probiotics is a promising approach for prevention of Vibrio infections in aquaculture. A probiotic anti-Vibrio strain, Bacillus pumilus H2, was characterized, and the mechanism of its effect was investigated. All 29 Vibrio strains tested were growth-inhibited by H2. The anti-Vibrio substance present in cell-free supernatant of H2 was purified and characterized by reversed-phase HPLC. Minimum inhibitory concentrations of the purified substance, determined in liquid media for various Vibrio strains, ranged from 0.5 to 64 µg/ml. Addition of the purified substance to Vibrio vulnificus culture inhibited cell growth (estimated by OD600). Confocal microscopy and scanning electron microscopy analyses showed that surface structure of V. vulnificus cells was damaged by the purified substance, as reflected by presence of membrane holes, disappearance of cellular contents, and formation of cell cavities. The major mechanism of this anti-Vibrio activity appeared to involve disruption of cell membranes, and consequent cell lysis. The purified anti-Vibrio substance was shown to be structurally identical to amicoumacin A by MS and NMR analysis. Our findings indicate that B. pumilus H2 has strong potential for prevention or treatment of fish vibriosis in the aquaculture industry.

Five new iridoids from Patrinia rupestris.

Five new iridoids, namely rupesin A-E (1-5, resp.), together with six known iridoids, 6-11, were isolated from the roots of Patrinia rupestris. Their structures were elucidated by spectroscopic methods including IR, UV, MS, and 1D- and 2D-NMR experiments, and comparison with data of known analogues. Compounds 4 and 11, compounds 1, 2, 5, 6, 8, 9, and 10, and compounds 3, 4, and 8 showed significant antibacterial activities against Bacillus subtilis, Escherichia coli, and Staphylococcus aureus, respectively.

New ambuic acid derivatives from the solid culture of Pestalotiopsis neglecta and their nitric oxide inhibitory activity.

Four new ambuic acid derivatives (1-4), and four known derivatives (5-8), were isolated from the solid culture of a plant pathogenic fungus Pestalotiopsis neglecta. Their structures were elucidated by extensive NMR experiments. The absolute configuration of the C-16 secondary alcohol in 1 was deduced via the CD data of the in situ formed [Rh2(OCOCF3)4] complex with the acetonide derivative of 1. The absolute configuration in 3 was assigned by comparison of the experimental and simulated electronic circular dichroism (ECD) spectrum. The NMR data of compound 5 was reported for the first time. In the nitric oxide (NO) inhibition assay, compounds 4, 6 and 7 showed inhibitory activity against the NO production in the lipopolysaccharide (LPS)-induced macrophage with IC50 values of 88.66, 11.20, and 20.80 µM, respectively.

Two new compounds from Ligularia dolichobotrys.

Two new compounds, a stigmasterol (1) and an eremophilenolide (2), were isolated from Ligularia dolichobotrys (Diels) together with ten known sesquiterpenoids, two known triterpenes and five known sterols. Their structures were elucidated by spectroscopic methods (IR, MS, 1H, 13C and 2D NMR). In addition, bakkenolide A (3) exhibited effective antitumor activity to human leukemia cells (HL-60), human hepatoma cells (Bel-7402) and human ovarian neoplasm cells (HO-8910).

Terpenes from Juniperus przewalskii and their antitumor activities.

Two new diterpenes were isolated from Juniperus przewalskii, together with 17 known terpense. Their structures were elucidated by spectroscopic methods (IR, MS, 1H, 13C and 2DNMR). In addition, 3 alpha-hinokiol (3) and 3 alpha-hydroxymannol (9) exhibited effective antitumor activities to cervical carcinoma (HeLa) and human ovarian carcinoma (HO-8910) cell lines.

New eremophilenolides from Cacalia pilgeriana.

Five new eremophilenolides and a known sesquiterpene were isolated from the methanol extract of the roots of Cacalia pilgeriana. Their structures were identified as 1 beta-hydroxy-2 beta-methyl-senecioyloxyeremophil-7(11)-en-8 beta(12)-olide (1), 1 beta-hydroxy-2 beta-methylsenecioyloxy-8 alpha-methoxyeremophil-7(11)-en- 8 beta(12)-olide, 2 beta-hydroxy-3 beta-methylsenecioyloxyeremophil-7(11)-en-8 alpha(12)-olide ( 3), 2 beta,8 beta-dihydroxy-3 beta-methylsenecioyloxyeremophil-7(11)-en-8 alpha(12)-olide and 1 beta,8 beta-dihydroxy-2 beta,3 alpha-diangeloyloxyeremophil-7(11)-en-8 alpha(12)-olide ( 5) and caryolane-1,9 beta-diol by spectroscopic methods including 2D-NMR techniques ( (1)H- (1)H COSY, HMQC, HMBC) and HR-ESI-MS. The structure and relative stereochemistry of compound 1 were unequivocally established by X-ray diffraction analysis. Bioassays showed compounds 3 and 5 to possess strong cytotoxic activity in vitro against human leukemia cells (HL-60) (IC (50) < 15 microg mL (-1)). The structure-activity relationship is discussed.