Sangkeun Son

Trapa japonica Pericarp Extract Reduces LPS-Induced Inflammation in Macrophages and Acute Lung Injury in Mice

In this study, we found that chloroform fraction (CF) from TJP ethanolic extract inhibited lipopolysaccharide (LPS)-induced production of nitric oxide (NO) and intracellular ROS in RAW264.7 cells. In addition, expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) genes was reduced, as evidenced by western blot. Our results indicate that CF exerts anti-inflammatory effects by down-regulating expression of iNOS and COX-2 genes through inhibition of MAPK (ERK, JNK and p38) and NF-κB signaling. Similarly we also evaluated the effects of CF on LPS-induced acute lung injury. Male Balb/c mice were pretreated with dexamethasone or CF 1 h before intranasal instillation of LPS. Eight hours after LPS administration, the inflammatory cells in the bronchoalveolar lavage fluid (BALF) were determined. The results indicated that CF inhibited LPS-induced TNF-α and IL-6 production in a dose dependent manner. It was also observed that CF attenuated LPS-induced lung histopathologic changes. In conclusion, these data demonstrate that the protective effect of CF on LPS-induced acute lung injury (ALI) in mice might relate to the suppression of excessive inflammatory responses in lung tissue. Thus, it can be suggested that CF might be a potential therapeutic agent for ALI.

Ulleungamides A and B, Modified α,β-Dehydropipecolic Acid Containing Cyclic Depsipeptides from Streptomyces sp. KCB13F003

Two novel cyclic depsipeptides, ulleungamides A (1) and B (2), were isolated from cultures of terrestrial Streptomyces sp. Their structures were determined by analyses of spectroscopic data and various chemical transformations, including modified Moshers method, advanced Marfeys method, PGME, GITC derivatizations, and Snatzkes method. Ulleungamides were determined to be a new class of peptides bearing unprecedented units, such as 5-hydroxy-6-methyl-2,3-dehydropipecolic acid, 4,5-dihydroxy-6-methyl-2,3-dehydropipecolic acid, and amino-linked 2-isopropylsuccinic acid. Ulleungamide A displayed growth inhibitory activity against Staphylococcus aureus and Salmonella typhimurium without cytotoxicity.

New Cyclic Lipopeptides of the Iturin Class Produced by Saltern-Derived Bacillus sp. KCB14S006

Salterns, one of the most extreme natural hypersaline environments, are a rich source of halophilic and halotolerant microorganisms, but they remain largely underexplored ecological niches in the discovery of bioactive secondary metabolites. In continued efforts to investigate the metabolic potential of microbial populations from chemically underexplored sites, three new lipopeptides named iturin F1, iturin F2 and iturin A9 (1–3), along with iturin A8 (4), were isolated from Bacillus sp. KCB14S006 derived from a saltern. The structures of the isolated compounds were established by 1D-, 2D-NMR and HR-ESIMS, and their absolute configurations were determined by applying advanced Marfey’s method and CD spectroscopy. All isolates exhibited significant antifungal activities against various pathogenic fungi and moderate cytotoxic activities toward HeLa and srcts-NRK cell lines. Moreover, in an in vitro enzymatic assay, compound 4 showed a significant inhibitory activity against indoleamine 2,3-dioxygenase.

Structures and biological activities of azaphilones produced by Penicillium sp. KCB11A109 from a ginseng field.

Twelve metabolites, including five highly oxygenated azaphilones, geumsanols A-E, along with seven known analogues were isolated from Penicillium sp. KCB11A109, a fungus derived from a ginseng field. Their structures were assigned by spectroscopic means (NMR and MS), and stereochemistries were determined by extensive spectroscopic analyses ((1)H-(1)H coupling constants, NOESY, and HETLOC) and chemical derivatizations (modified Moshers method and acetonide formation). The isolates were evaluated for their anticancer, antimicrobial, antimalarial activities, and phenotypic effects in zebrafish development. Of these compounds possessing no pyranoquinone core, only geumsanol E exhibited cytotoxic activities and toxic effects on zebrafish embryos, suggesting that a double bond at C-11 and C-12 is important for biological activity.

Haenamindole, an unusual diketopiperazine derivative from a marine-derived Penicillium sp. KCB12F005.

During the chemical investigation of marine-derived fungus, an unusual diketopiperazine (DKP) alkaloid, haenamindole (1), was isolated from a culture of the marine-derived fungus Penicillium sp. KCB12F005. The structure of 1, which possesses benzyl-hydroxypiperazindione and phenyl-pyrimidoindole rings system in the molecule, was elucidated by analysis of NMR and MS data. The stereochemistry of 1 was determined by ROESY and advanced Marfeys method.

Genomics-Driven Discovery of Chlorinated Cyclic Hexapeptides Ulleungmycins A and B from a Streptomyces Species

Analysis of the genome sequence of Streptomyces sp. KCB13F003 showed the presence of a cryptic gene cluster encoding flavin-dependent halogenase and nonribosomal peptide synthetase. Pleiotropic approaches using multiple culture media followed by LC-MS-guided isolation and spectroscopic analysis enabled the identification of two new chlorinated cyclic hexapeptides, ulleungmycins A and B (1 and 2). Their structures, including absolute configurations, were determined by 1D and 2D NMR techniques, advanced Marfeys analysis, and GITC derivatization. The new peptides, featuring unusual amino acids 5-chloro-l-tryptophan and d-homoleucine, exhibited moderate antibacterial activities against Gram-positive pathogenic bacteria including methicillin-resistant and quinolone-resistant Staphylococcus aureus.

The Fungal Metabolite Brefeldin A Inhibits Dvl2-Plk1-Dependent Primary Cilium Disassembly

The primary cilium is a non-motile microtubule-based organelle that protrudes from the surface of most human cells and works as a cellular antenna to accept extracellular signals. Primary cilia assemble from the basal body during the resting stage (G0 phase) and simultaneously disassemble with cell cycle re-entry. Defective control of assembly or disassembly causes diverse human diseases including ciliopathy and cancer. To identify the effective compounds for studying primary cilium disassembly, we have screened 297 natural compounds and identified 18 and 17 primary cilium assembly and disassembly inhibitors, respectively. Among them, the application of KY-0120, identified as Brefeldin A, disturbed Dvl2-Plk1-mediated cilium disassembly via repression of the interaction of CK1ɛ-Dvl2 and the expression of Plk1 mRNA. Therefore, our study may suggest useful compounds for studying the cellular mechanism of primary cilium disassembly to prevent ciliopathy and cancer.

Anti-inflammatory phomalichenones from an endolichenic fungus Phoma sp.

Four new compounds, phomalichenones A–D (1–4), and seven known compounds (5–11) were isolated from the cultures of an endolichenic fungus Phoma sp. EL002650. Their structures were determined by the analysis of their spectroscopic data (NMR and MS). Compounds 1 and 6 inhibited nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. In addition, compound 1 diminished the protein expression levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and decreased the mRNA expression levels of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin(IL)-1β, and IL-6.

Antibacterial Cyclic Lipopeptide Enamidonins with an Enamide-Linked Acyl Chain from a Streptomyces Species

Three cyclic lipopeptides, including one known (1) and two new (2 and 3) compounds, that possess the rare enamide linkage group were discovered from Streptomyces sp. KCB14A132, an actinobacterium isolated from a soil sample collected from Jeung Island, Korea. The NMR and MS-based characterization showed that they differed in the amino acid residues in the peptide backbone. Application of Marfeys analysis, GITC derivatization, and modified Moshers method, as well as ECD measurements provided the absolute configurations of enamidonin (1) and those of new compounds enamidonins B and C (2 and 3). The two new enamidonin analogues were shown to exhibit antibacterial activity against Gram-positive bacteria including methicillin-resistant and quinolone-resistant Staphylococcus aureus. Furthermore, evaluation of the extraction conditions and a close inspection of the LC-MS chromatograms revealed that the N, N-acetonide unit of the enamidonin family was formed during the acetone extraction process. The chemically prepared deacetonide derivatives of enamidonins were found to lack antibacterial activity, demonstrating that the dimethylimidazolidinone residue is necessary for antibacterial activity.

Ulleungdin, a Lasso Peptide with Cancer Cell Migration Inhibitory Activity Discovered by the Genome Mining Approach

The advances of genomic sequence analyses and genome mining tools have enabled the exploration of untapped microbial natural products. Through genome mining studies to discover cryptic natural products, we found biosynthetic genes encoding a new lasso peptide in the genome sequence of a soil bacterium, Streptomyces sp. KCB13F003 isolated from Ulleung Island (a small volcanic island), Korea. The production and purification of the encoded peptide, named ulleungdin, were achieved by optimizing the culture conditions followed by LC-MS-targeted isolation. Structure elucidation was performed by NMR spectroscopic and MS spectrometric analyses and chemical means (Marfeys and GITC derivatizations), proving ulleungdin to be a new 15-mer class II lasso peptide with a threaded structure. Biological evaluation with the cell invasion assay and time-lapse cell tracking analysis revealed that ulleungdin has significant inhibitory activities against cancer cell invasion and migration.