Two new cytotoxic indole alkaloids from a deep-sea sediment derived metagenomic clone

Palladium-catalyzed α-arylation of indolin-3-ones

A method for the catalytic α-arylation of indolin-3-ones was developed. The catalytic system comprising Pd(dba)₂ and PAd₃ was found to be optimal for the transformation. The protocol features broad functional group compatibility in that a range of arylated indoxyl derivatives bearing a fully substituted carbon center was synthesized with high efficiency. A preliminary bioassay study revealed that the selected indole-substituted indolin-3-ones exhibit favorable cytotoxic activities against HCT-116 cancer cell line.

Two New Cytotoxic Compounds from a Deep-Sea Penicillum citreonigrum XT20-134

Penicillum citreonigrum XT20-134 (MCCC 3A00956) is a fungus with cytotoxic activity, derived from deep-sea sediment. Five new compounds, adeninylpyrenocine (1), 2-hydroxyl-3-pyrenocine-thio propanoic acid (2), ozazino-cyclo-(2,3-dihydroxyl-trp-tyr) (3), 5,5-dichloro-1-(3,5-dimethoxyphenyl)-1,4-dihydroxypentan-2-one (4), and 2,3,4-trihydroxybutyl cinnamate (5), together with 19 known compounds (6-24), were isolated from an ethyl acetate (EtOAc) extract of its fermentation. The structures of the new compounds were comprehensively characterized by high-resolution electrospray ionization-mass spectrometry (HR-ESI-MS), 1D and 2D nuclear magnetic resonance (NMR). All isolates were evaluated for their cytotoxic activities. The heteroatom-containing new compounds 2 and 4 showed potent cytotoxicity to the human hepatoma tumor cell Bel7402 with IC₅₀ values of 7.63 ± 1.46, 13.14 ± 1.41 μM and the human fibrosarcoma tumor cell HT1080 with IC₅₀ values of 10.22 ± 1.32, 16.53 ± 1.67 μM, respectively.

Antibiotics from Deep-Sea Microorganisms: Current Discoveries and Perspectives

The increasing emergence of new forms of multidrug resistance among human pathogenic bacteria, coupled with the consequent increase of infectious diseases, urgently requires the discovery and development of novel antimicrobial drugs with new modes of action. Most of the antibiotics currently available on the market were obtained from terrestrial organisms or derived semisynthetically from fermentation products. The isolation of microorganisms from previously unexplored habitats may lead to the discovery of lead structures with antibiotic activity. The deep-sea environment is a unique habitat, and deep-sea microorganisms, because of their adaptation to this extreme environment, have the potential to produce novel secondary metabolites with potent biological activities. This review covers novel antibiotics isolated from deep-sea microorganisms. The chemical classes of the compounds, their bioactivities, and the sources of organisms are outlined. Furthermore, the authors report recent advances in techniques and strategies for the exploitation of deep-sea microorganisms.

Production and Identification of Inthomycin B Produced by a Deep-Sea Sediment-Derived Streptomyces sp. YB104 Based on Cultivation-Dependent Approach

The natural products discovery program in our group utilizes deep-sea sediment-derived microorganisms and employs a bio-active guided isolation procedure and one strain many compounds (OSMAC) approach to screen bio-active natural products for practical applications in the medicinal and agricultural industry. OSMAC strategy is employed to stimulate secondary metabolite production through changing culture conditions. In this paper, we applied cultivation-dependent procedure, changing media type, leading to the discovery of a bio-active compound named inthomycin B (1) from a marine-derived Streptomyces sp. YB104. The compound was characterized based on extensive spectroscopic analyses and comparison to that in the reported literature. The quantification of inthomycin B demonstrated that Streptomyces sp. YB104 produced moderate yield of inthomycin B with a yield around 25 mg/l after 14 days. Thus, Streptomyces sp. YB104 was considered to be a useful potential as a first industrial-producing strain of inthomycins.

Biosynthetic Functional Gene Analysis of Bis-Indole Metabolites from 25D7, a Clone Derived from a Deep-Sea Sediment Metagenomic Library

This work investigated the metabolites and their biosynthetic functional hydroxylase genes of the deep-sea sediment metagenomic clone 25D7. 5-Bromoindole was added to the 25D7 clone derived Escherichia coli fermentation broth. The new-generated metabolites and their biosynthetic byproducts were located through LC-MS, in which the isotope peaks of brominated products emerged. Two new brominated bis-indole metabolites, 5-bromometagenediindole B (1), and 5-bromometagenediindole C (2) were separated under the guidance of LC-MS. Their structures were elucidated on the basis of 1D and 2D NMR spectra (COSY, HSQC, and HMBC). The biosynthetic functional genes of the two new compounds were revealed through LC-MS and transposon mutagenesis analysis. 5-Bromometagenediindole B (1) also demonstrated moderately cytotoxic activity against MCF7, B16, CNE2, Bel7402, and HT1080 tumor cell lines in vitro.

Marine natural products

This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1378 in 456 papers for 2014), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Marine Indole Alkaloids

Marine indole alkaloids comprise a large and steadily growing group of secondary metabolites. Their diverse biological activities make many compounds of this class attractive starting points for pharmaceutical development. Several marine-derived indoles were found to possess cytotoxic, antineoplastic, antibacterial and antimicrobial activities, in addition to the action on human enzymes and receptors. The newly isolated indole alkaloids of marine origin since the last comprehensive review in 2003 are reported, and biological aspects will be discussed.