Kiamycins B and C,unusual bridged angucyclinones from a marine sediment-derived Streptomyces sp.

Kiamycins B (1) and C (2), two unusual angucyclinones bearing a novel 6,12-epoxybenz[a]anthracene ring system, were isolated from the cultures of a marine sediment-derived Streptomyces sp. along with one structurally related derivative 3. Their structures and stereochemistries were determined by spectroscopic analyses, single-crystal X-ray diffraction and electronic circular dichroism (ECD) calculations.     

New polycyclic tetramate macrolactams from marine-derived Streptomyces sp. SCSIO 40060

Polycyclic tetramate macrolactams (PTMs) are widely distributed in nature and are generated from a compact biosynthetic pathway. Bioinformatics analysis of the draft genome sequence of marine-derived Streptomyces sp. SCSIO 40060 revealed the presence of a putative PTM-encoding biosynthetic gene cluster (BGC). Comparison of this PTM BGC with those from the databank by genome mining suggests that Streptomyces sp. SCSIO 40060 should produce PTMs with a 5/6/5 type of carbocyclic ring. Subsequently, a 40-L scale of cultivation of Streptomyces sp. SCSIO 40060 led to the isolation and characterization of four known PTMS, ikarugamycin (1), epoxyikarugamycin (2), capsimycin (3), capsimycin C (4), and three new PTMs, hydroxyikarugamycins A–C (5–7). The planar structures of 5–7 were assigned by comprehensive spectroscopic analysis and the absolute configurations of 5 and 6 were unequivocally determined by X-ray diffraction analysis. The absolute structure of 7 was deduced by comparing ECD spectra of 5–7. Capsimycin (3) showed antimicrobial activity against methicillin-resistant Staphylococcus aureus with a MIC value of 16?μg/mL and displayed cytotoxicity against several cancer cell lines with IC₅₀ values ranging from 2.62 to 6.87?μM.     

New Scabimycins A-C Isolated from Streptomyces acidiscabies (Lu19992)

Peptide natural products displaying a wide range of biological activities have become important drug candidates over the years. Microorganisms have been a powerful source of such bioactive peptides, and Streptomyces have yielded many novel natural products thus far. In an effort to uncover such new, meaningful compounds, the metabolome of Streptomyces acidiscabies was analyzed thoroughly. Three new compounds, scabimycins A–C (1–3), were discovered, and their chemical structures were elucidated by NMR spectroscopy. The relative and absolute configurations were determined using ROESY NMR experiments and advanced Marfey’s method.     

Xantholipin, a novel inhibitor of HSP47 gene expression produced by Streptomyces sp.

In the course of our screening program to identify inhibitors of HSP47 gene expression, we obtained a novel aromatic substance from Streptomyces sp. named Xantholipin. Its structure was determined based on physicochemical data of Xantholipin and its derivatives. The absolute configuration was also established by the modified Mosher's method.     

A new antimalarial polyether from a marine Streptomyces sp. H668

The antimalarial guided fractionation of the culture of marine Streptomyces sp. strain H668 led to the isolation of a new polyether metabolite. The structure was determined by comprehensive NMR and MS assignments. This new metabolite showed in vitro antimalarial activity against both the chloroquine-susceptible (D6) and-resistant (W2) clones of Plasmodium falciparum, without cytotoxicity to normal cells (Vero) making it a promising first lead from this marine bacterium.     

Synthetic studies on basidifferquinones: the first synthesis of (±)-basidifferquinone C

Basidifferquinones, isolated from Streptomyces sp., are potent inducers for fruiting-body formation of a basidiomycete Polyporus arcularius. Construction of the basic framework of basidifferquinones and the first synthesis of (±)-basidifferquinone C were accomplished by starting from 3,5-dihydroxy-2-naphthoic acid.     

Rhamnosylation of lignans by a Streptomyces strain

Screening of 400 Streptomyces strains for biotransformation of the natural lignan matairesinol led to the identification of Streptomyces sp. LS136, capable of producing a single metabolite in moderate yields. Isolation and purification by preparative HPLC, followed by structural analyses by LC-MS and NMR, established the structure as matairesinol-4-O-rhamnoside. This bacterial strain was also used for rhamnosylation of the abundant natural lignans, hydroxymatairesinol and secoisolariciresinol.     

Heronamycin A: a new benzothiazine ansamycin from an Australian marine-derived Streptomyces sp.

Chemical analysis of a marine-derived Streptomyces sp. (CMB-M0392) isolated from sediment collected off Heron Island, Queensland, Australia, yielded a new benzothiazine ansamycin, heronamycin A. The absolute stereostructure of heronamycin A was determined by detailed spectroscopic analysis and X-ray crystallography. Heronamycin A exhibited modest antimicrobial activity against Bacillus subtilis strains ATCC 6051 and 6633 (IC₅₀ = 18 and 14 μM, respectively).     

The isolation, structural determination, and total synthesis of terfestatin A, a novel auxin signaling inhibitor from Streptomyces sp.

Indole 3-acetic acid, a plant hormone auxin, regulates every aspects of plant growth and development. In the screening for specific inhibitors on auxin signaling using the transgenic Arabidopsis plant harboring the auxin-responsive reporter gene, terfestain A was found to be a novel inhibitor of auxin signaling from the culture of Streptomyces sp. F40. The structure of terfestatin A was determined to be p-terphenyl β-glucoside on the basis of spectroscopic analyses, chemical degradation, and total synthesis.     

Revised structure of tetrapetalone A and its absolute stereochemistry

The chemical structure of tetrapetalone A (1), a novel lipoxygenase inhibitor from Streptomyces sp., was revised by using the ¹H-¹⁵N HMBC technique. Furthermore, the absolute stereochemistry of all the asymmetric carbons in 1 was determined based on the detailed NOE data of 1 and its derivative.     

Cyclodysidins A–D,cyclic lipopeptides from the marine sponge-derived Streptomyces strain RV15

Four new cyclic lipopeptides, cyclo-(AFA-Ser-Gln-Asn-Tyr-Asn-Ser-Thr), named cyclodysidins A–D, were isolated from the broth culture of Streptomyces strain RV15 associated with the marine sponge Dysidea tupha. The sequences of the amino acid building blocks in the compounds and their structures were determined by 1D- and 2D-NMR techniques and CID-MS/MS experiments. The absolute configurations of all α-amino acids were determined by HPLC analysis after derivatization with Marfey’s reagent and comparison with commercially available reference samples, while those two of the β-amino fatty acids were determined by using racemic and enantiopure reference samples synthetically prepared.     

Hainanmycin A,a cyclo-heptadeca macrolide bearing a cyclopentenone moiety from the mangrove-derived Streptomyces sp. 219807

A macrocyclic polyketide with novel carbon skeleton, namely hainanmycin A, was isolated from the mangrove-derived Streptomyces sp. 219807. This polycyclic compound featured a cyclo-heptadeca framework possessing a 5,6-disubstituted-4-hydroxy-2-pyrone moiety in conjunction with a 2-cyclopentenone residue. The structure was established by spectroscopic analyses, and the stereochemistry was determined by NMR chemical shifts calculations and time-dependent density functional theory (TDDFT) calculation of electronic circulardichroism (ECD). A possible biogenetic pathway for hainanmycin A was proposed.     

New Kendomycin Derivative Isolated from Streptomyces sp. Cl 58-27

In the course of screening new streptomycete strains, the strain Streptomyces sp. Cl 58-27 caught our attention due to its interesting secondary metabolite production profile. Here, we report the isolation and characterization of an ansamycin natural product that belongs structurally to the already known kendomycins. The structure of the new kendomycin E was elucidated using NMR spectroscopy, and the corresponding biosynthetic gene cluster was identified by sequencing the genome of Streptomyces sp. Cl 58-27 and conducting a detailed analysis of secondary metabolism gene clusters using bioinformatic tools.     

The syntheses of rac-inthomycin A, (+)-inthomycin B and (+)-inthomycin C using a unified synthetic approach

The Stille coupling between a common oxazole vinyl iodide and stereodefined stannyl-diene units is described as the cornerstone of a unified synthetic route to the inthomycin family of bioactive Streptomyces metabolites. This procedure has been utilised to prepare (+)-inthomycin B and (+)-inthomycin C for the first time; in these examples the stereogenic centre was introduced using the Kiyooka ketene acetal/amino acid-derived oxazaborolidinone variant of the Mukaiyama aldol reaction. In addition, a convenient preparation of rac-inthomycin A is described based on the same strategy.     

Comparison of Glucose and Glycerol as Carbon Sources for ε-Poly-l-Lysine Production by Streptomyces sp. M-Z18

Glucose is widely used in the production of ε-poly-l-lysine (ε-PL); however, glycerol is an emerging carbon source for ε-PL production in recent years. Glycerol is superior to glucose for ε-PL production according to batch and fed-batch fermentations by Streptomyces sp. M-Z18 in this study. To elaborate this difference, physiological metabolism of Streptomyces sp. M-Z18 on glycerol has compared with glucose during batch fermentation. The activities of key enzymes showed that aspartate kinase (ASPK) and ε-PL synthetase (Pls) in glycerol medium was higher than those in glucose, and especially the activity of Pls could enhance by 2.3- and 3.6-fold at 24 and 36 h, respectively. Moreover, metabolism flux analysis demonstrated that a 25 % higher fluxes derived from glycerol are directed into ε-PL synthesis than glucose. As a result, the mechanism of glycerol better than glucose is determined: the activities of ASPK and Pls in glycerol higher than those in glucose, and result in carbon fluxes directed into ε-PL synthesis increased. This study offers a reference to substitute glycerol for conventional glucose as carbon source for ε-PL production.     

Tetrapetalone A, a novel lipoxygenase inhibitor from Streptomyces sp.

Tetrapetalone A (I), C₂₆H₃₃O₇N, is a novel lipoxygenase inhibitor isolated from a culture filtrate of Streptomyces sp. USF-4727 strain. Its chemical structure was determined by its spectroscopic evidence and methylation with diazomethane. The stereochemistry was investigated by the coupling constant in ¹H NMR, NOESY data and modified Mosher's method. I possessed a tetracyclic skeleton and a β-rhodinosyl moiety, and this is the first report of a compound with such a tetracyclic skeleton.     

Enzymatic Production of Ferulic Acid from Defatted Rice Bran by Using a Combination of Bacterial Enzymes

Ferulic acid (FA), which is present in the cell walls of some plants, is best known for its antioxidant property. By combining a commercial enzyme that shows FA esterase activity with several Streptomyces carbohydrate-hydrolyzing enzymes, we succeeded in enhancing the enzymatic production of FA from defatted rice bran. In particular, the combination of three xylanases, an α-l-arabinofuranosidase, and an acetyl xylan esterase from Streptomyces spp. produced the highest increase in the amount of released FAs among all the enzymes in the Streptomyces enzymes library. This enzyme combination also had an effect on FA production from other biomasses, such as raw rice bran, wheat bran, and corncob.     

Direct formation of chromopyrrolic acid from indole-3-pyruvic acid by StaD, a novel hemoprotein in indolocarbazole biosynthesis

Indole-3-pyruvic acid was transformed to chromopyrrolic acid by a novel heme-containing enzyme StaD responsible for staurosporine biosynthetic pathway in Streptomyces sp. TP-A0274.     

Isolation,screening and characterization of uranium microremediable actinomycetes from fallen leaves of Azadirachta indica in Western Ghats

Microremediation of harmful radioactive waste such as uranium has been carried out by the endophytic actinomycetes strains isolated from the unnoticed fallen leaves of commonly available medicinal plant Azadirachta indica, which are considered as unique source. Among six actinobacteria isolates, one microbe (A5) effectively removed uranium in 12 h at temperature 30 °C and pH 8–9. Molecular characterization and phylogenetic analysis support the classification of the isolate A5 as a new strain which was named as Streptomyces sp. MINIYAA7 (Genbank accession number KF909129).     

Recently Discovered Secondary Metabolites from Streptomyces Species

The Streptomyces genus has been a rich source of bioactive natural products, medicinal chemicals, and novel drug leads for three-quarters of a century. Yet studies suggest that the genus is capable of making some 150,000 more bioactive compounds than all Streptomyces secondary metabolites reported to date. Researchers around the world continue to explore this enormous potential using a range of strategies including modification of culture conditions, bioinformatics and genome mining, heterologous expression, and other approaches to cryptic biosynthetic gene cluster activation. Our survey of the recent literature, with a particular focus on the year 2020, brings together more than 70 novel secondary metabolites from Streptomyces species, which are discussed in this review. This diverse array includes cyclic and linear peptides, peptide derivatives, polyketides, terpenoids, polyaromatics, macrocycles, and furans, the isolation, chemical structures, and bioactivity of which are appraised. The discovery of these many different compounds demonstrates the continued potential of Streptomyces as a source of new and interesting natural products and contributes further important pieces to the mostly unfinished puzzle of Earth’s myriad microbes and their multifaceted chemical output.