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Two new proton-deficient metabolites, tandocyclinones A and B ( 1 and 2 ), were discovered via the chemical profiling of the Streptomyces sp. strain TDH03, which was isolated from a marine sediment sample collected from the intertidal mudflat in Tando Port, the Republic of Korea. The structures of 1 and 2 were elucidated as new ether-bridged C -glycosyl benz[ a ]anthracenes by using a combination of spectroscopic analyses of ultraviolet (UV) and mass spectrometry (MS) data, along with nuclear magnetic resonance (NMR) spectra, which were acquired in tetrahydrofuran (THF)- d 8 selected after an extensive search for a solvent, resulting in mostly observable exchangeable protons in the 1 H NMR spectrum. Their configurations were successfully assigned by applying a J -based configuration analysis, rotating-frame Overhauser enhancement spectroscopy (ROESY) NMR correlations, chemical derivatization methods based on NMR (a modified version of Mosher's method) and circular dichroism (CD) (Snatzke's method using Mo 2 (OAc) 4 -induced CD), as well as quantum-mechanics-based computational methods, to calculate the electronic circular dichroism (ECD). Tandocyclinones A and B ( 1 and 2 ) were found to have weak antifungal activity against Trichophyton mentagrophytes IFM40996 with an MIC value of 128 μg/mL (244 and 265 μM for 1 and 2 , respectively). A further biological evaluation revealed that tandocyclinone A ( 1 ) displayed inhibitory activity against Mycobacterium avium (MIC 50 = 40.8 μM) and antiproliferative activity against SNU638 and HCT116 cancer cells, with IC 50 values of 31.9 µM and 49.4 µM, respectively.

Four new chlorinated cycloaromatized enediyne compounds, jejucarbosides B-E ( 1 - 4 ), were discovered together with previously-identified jejucarboside A from a marine actinomycete strain. Compounds 1 - 4 were identified as new chlorinated cyclopenta[ a ]indene glycosides based on 1D and 2D nuclear magnetic resonance, high-resolution mass spectrometry, and circular dichroism (CD) spectra. Jejucarbosides B and E bear a carbonate functional group whereas jejucarbosides C and D are variants possessing 1,2-diol by losing the carbonate functionality. It is proposed that the production of 1 - 4 occurs via Bergman cycloaromatization capturing Cl - and H + in the alternative positions of a p -benzyne intermediate derived from a 9-membered enediyne core. Jejucarboside E ( 4 ) displayed significant cytotoxicity against human cancer cell lines including SNU-638, SK-HEP-1, A549, HCT116, and MDA-MB-231, with IC 50 values of 0.31, 0.40, 0.25, 0.29, and 0.48 μM, respectively, while jejucarbosides B-D ( 1 - 3 ) showed moderate or no cytotoxic effects.

Streptomyces sp. GET02.ST and Achromobacter sp. GET02.AC were isolated together from the gut of the wharf roach, Ligia   exotica , inhabiting the intertidal zone of the west coast of Korea. The co-cultivation of these two strains significantly induced the production of two new metabolites, ligiamycins A ( 1 ) and B ( 2 ), which were barely detected in the single culture of Streptomyces sp. GET02.ST. The planar structures of ligiamycins A ( 1 ) and B ( 2 ) were elucidated as new decalins coupled with amino-maleimides by the analysis of various spectroscopic data, including nuclear magnetic resonance (NMR), ultraviolet (UV), and mass (MS) data. The assignment of two nitrogen atoms in amino-maleimide in 1 was accomplished based on 1 H- 15 N heteroatom single quantum coherence spectroscopy (HSQC) NMR experiments. The relative configurations of the ligiamycins were determined using rotating frame Overhauser effect spectroscopy (ROESY) NMR data, and their absolute configurations were deduced by comparing their experimental and calculated optical rotations. Ligiamycin A ( 1 ) displayed antibacterial effects against Staphylococcus aureus and Salmonella enterica , while ligiamycin B ( 2 ) exhibited mild cell cytotoxicity against human colorectal cancer cells.

Two new secondary metabolites, svalbamides A ( 1 ) and B ( 2 ), were isolated from a culture extract of Paenibacillus sp. SVB7 that was isolated from surface sediment from a core (HH17-1085) taken in the Svalbard archipelago in the Arctic Ocean. The combinational analysis of HR-MS and NMR spectroscopic data revealed the structures of 1 and 2 as being lipopeptides bearing 3-amino-2-pyrrolidinone, d-valine, and 3-hydroxy-8-methyldecanoic acid. The absolute configurations of the amino acid residues in svalbamides A and B were determined using the advanced Marfey's method, in which the hydrolysates of 1 and 2 were derivatized with l- and d- forms of 1-fluoro-2,4-dinitrophenyl-5-alanine amide (FDAA). The absolute configurations of 1 and 2 were completely assigned by deducing the stereochemistry of 3-hydroxy-8-methyldecanoic acid based on DP4 calculations. Svalbamides A and B induced quinone reductase activity in Hepa1c1c7 murine hepatoma cells, indicating that they represent chemotypes with a potential for functioning as chemopreventive agents.

Chemical profiling of the Streptomyces sp. strain SUD119, which was isolated from a marine sediment sample collected from a volcanic island in Korea, led to the discovery of three new metabolites: donghaecyclinones A-C ( 1 - 3 ). The structures of 1 - 3 were found to be rearranged, multicyclic, angucyclinone-class compounds according to nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. The configurations of their stereogenic centers were successfully assigned using a combination of quantum mechanics-based computational methods for calculating the NMR shielding tensor (DP4 and CP3) as well as electronic circular dichroism (ECD) along with a modified version of Mosher's method. Donghaecyclinones A-C ( 1 - 3 ) displayed cytotoxicity against diverse human cancer cell lines (IC 50 : 6.7-9.6 μM for 3 ).