7 research outputs found
A new actinomycin Z analogue with an additional oxygen bridge between chromophore and <i>β</i>-depsipentapeptide from <i>Streptomyces</i> sp. KIB-H714
<p>Actinomycin Z<sub>6</sub> (<b>1</b>), a new member of the actinomycin family, along with three congeners of the Z-type (Z<sub>1</sub>, Z<sub>3</sub>, Z<sub>5</sub>) actinomycins, are produced from <i>Streptomyces</i> sp. KIB-H714. Their structures were authenticated by comprehensive spectroscopic data interpretation. Different from all the reported Z-type actinomycins, the <i>β</i>-ring of the new compound actinomycin Z<sub>6</sub> includes an additional ring linked between the actinoyl chromophore and <i>β</i>-peptidolactone. In Z<sub>3</sub> and Z<sub>5</sub>, the L-threonine in <i>β</i>-depsipeptide is replaced by the unusual 4-chlorothreonine, an amino acid rarely found in actinomycin family. All isolates were evaluated for cytotoxicity against five human tumor cell lines and for inhibitory activity against <i>Candida albicans</i> and <i>Staphylococcus aureus</i>.</p
Tropolone Ring Construction in the Biosynthesis of Rubrolone B, a Cationic Tropolone Alkaloid from Endophytic <i>Streptomyces</i>
Rubrolones
are tropolonoid natural products with a unique carbon
skeleton. Extensive secondary metabolite analysis of the endophytic <i>Streptomyces</i> sp. KIB-H033 revealed a new class of rubrolone
analogue possessing a rare benzoic acid–pyridine inner salt
moiety. Precursor feeding with [<sup>13</sup>C]-acetate revealed a
labeling pattern consistent with tropolone moiety construction via
type-II PKS chemistry followed by complex oxidative rearrangements.
This bacterial biosynthetic route represents a surprising departure
from fungal tropolone assembly during stipitatic acid biosynthesis
New Duclauxamide from <i>Penicillium manginii</i> YIM PH30375 and Structure Revision of the Duclauxin Family
Duclauxamide
A1 (<b>1</b>), a new polyketide-derived heptacyclic
oligophenalenone dimer with a <i>N</i>-2-hydroxyethyl moiety,
was isolated from <i>Penicillium manginii</i> YIM PH30375.
Spectroscopic analysis, X-ray single crystal diffraction, and <sup>13</sup>C NMR DFT calculations confirmed that compound <b>1</b> and other duclauxin analogues possess the unified <i>S</i> configuration at C-9′, which corrects a long-standing misrepresentation
of duclauxins as C-9′<i>R</i> epimers. A plausible
biosynthetic pathway for duclauxins is proposed on the basis of previous
acetate labeling results for duclauxin and sclerodin
New Duclauxamide from <i>Penicillium manginii</i> YIM PH30375 and Structure Revision of the Duclauxin Family
Duclauxamide
A1 (<b>1</b>), a new polyketide-derived heptacyclic
oligophenalenone dimer with a <i>N</i>-2-hydroxyethyl moiety,
was isolated from <i>Penicillium manginii</i> YIM PH30375.
Spectroscopic analysis, X-ray single crystal diffraction, and <sup>13</sup>C NMR DFT calculations confirmed that compound <b>1</b> and other duclauxin analogues possess the unified <i>S</i> configuration at C-9′, which corrects a long-standing misrepresentation
of duclauxins as C-9′<i>R</i> epimers. A plausible
biosynthetic pathway for duclauxins is proposed on the basis of previous
acetate labeling results for duclauxin and sclerodin
Neaumycin: A New Macrolide from <i>Streptomyces</i> sp. NEAU-x211
Neaumycin, a new 30-membered macrolide featuring an internal diester bridge, a molecular architecture that is unprecedented among known macrolide natural products, was isolated from a soil actinomycete strain <i>Streptomyces</i> sp. NEAU-x211. The structure of neaumycin was elucidated on the basis of comprehensive mass and NMR spectroscopic interpretation, including the relative stereochemistry of four independent coupling systems
Natural and Semisynthetic Tigliane Diterpenoids with New Carbon Skeletons from <i>Euphorbia dracunculoides</i> as a Wnt Signaling Pathway Inhibitor
Euphordraculoates
A (<b>1</b>) and B (<b>2</b>), featuring
tigliane diterpenoids with two new carbon skeletons, were characterized
as metabolites of <i>Euphorbia dracunculoides</i> and semisynthetic
products, respectively. Their structures were determined by spectroscopic
analyses and X-ray crystallography. The respective biosynthetic and
chemical formation mechanisms for <b>1</b> and <b>2</b> from a known tigliane <b>3</b> was proposed. The detailed
decarbonization mechanism from <b>3</b> to <b>2</b> was
further explored by <sup>18</sup>O-labeling experiment. Compound <b>2</b> could inhibit Wnt pathway in a dose- and time-dependent
manner
Biosynthetic Potential-Based Strain Prioritization for Natural Product Discovery: A Showcase for Diterpenoid-Producing Actinomycetes
Natural products remain the best
sources of drugs and drug leads
and serve as outstanding small-molecule probes to dissect fundamental
biological processes. A great challenge for the natural product community
is to discover novel natural products efficiently and cost effectively.
Here we report the development of a practical method to survey biosynthetic
potential in microorganisms, thereby identifying the most promising
strains and prioritizing them for natural product discovery. Central
to our approach is the innovative preparation, by a two-tiered PCR
method, of a pool of pathway-specific probes, thereby allowing the
survey of all variants of the biosynthetic machineries for the targeted
class of natural products. The utility of the method was demonstrated
by surveying 100 strains, randomly selected from our actinomycete
collection, for their biosynthetic potential of four classes of natural
products, aromatic polyketides, reduced polyketides, nonribosomal
peptides, and diterpenoids, identifying 16 talented strains. One of
the talented strains, <i>Streptomyces griseus</i> CB00830,
was finally chosen to showcase the discovery of the targeted classes
of natural products, resulting in the isolation of three diterpenoids,
six nonribosomal peptides and related metabolites, and three polyketides.
Variations of this method should be applicable to the discovery of
other classes of natural products