Nigericin and grisorixin methyl ester from the Algerian soil-living Streptomyces youssoufiensis SF10 strain: a computational study on their epimeric structures and evaluation of glioblastoma stem cells growth inhibition

The present work describes the metabolites produced by a strain identified as Streptomyces youssoufiensis, whose secondary metabolites profile has not been studied so far. The crude ethyl acetate extract was analyzed by high performance liquid chromatography-electrospray ionization mass spectrometry, leading to the detection of the ionophoric polyethers nigericin, epinigericin, abierixin and the newly isolated grisorixin methyl ester. The presence of epimeric forms of nigericin/epinigericin and grisorixin/epigrisorixin has spurred density functional theory computational calculations. This analysis was able to provide the relative stability of the most favored epimers, setting the basis for general structural considerations applicable to several other polyethers. Both nigericin sodium salt and grisorixin methyl ester showed to affect glioblastoma stem cells proliferation in a dose-dependent manner, with a higher activity for the more lipophilic grisorixin methyl ester (GI₅₀ values of 3.85 and 3.05 μM for VIPI and COMI human glioblastoma stem cells, respectively).     

Two New 23‐Membered Macrolactones from a Terrestrial Bacterium,Streptomyces sp. IMBJ01

Two new unusual 23‐membered macrolactones, named griseoviridins B ( 1 ) and C ( 2 ), along with the known analogue griseoviridin ( 3 ) were isolated from the culture of Streptomyces sp. IMBJ01, a terrestrial bacterium isolated from Wolong, Sichuan Province, China. The structures of 1 and 2 were elucidated on the basis of extensive spectroscopic data and their absolute configurations were determined by comparison of their CD spectra with those of compound 3 .     

New approaches to the structural modification of olean-type pentacylic triterpenes via microbial oxidation and glycosylation

Microbial transformation of 4 olean-type pentacyclic triterpenes (OPTs), 3-oxo oleanolic acid (1), 3-acetyl oleanolic acid (2), oleanolic acid (3), and esculentoside A (4) was studied. After the screening of 12 strains of microbes, preparative biotransformation by two strains of Streptomyces griseus ATCC 13273 and Aspergillus ochraceus CICC 40330 resulted in the isolation of 10 metabolites. The microbial catalyzed high efficient regio-selective methyl oxidation and glycosylation were discovered, which could be provided as an alternative method to expand the structural diversity of OPTs. All the structures of the metabolites were elucidated unambiguously by ESI-MS, ¹H NMR, ¹³C NMR, and 2D-NMR spectroscopy.     

氦氖激光在红霉素链霉菌和龟裂链霉菌灭活原生质体融合中的应用Ⅰ──激光对灭活原生质体融合频率的影响

研究了He-Ne激光对红霉素链霉菌(streptomyc eserythreus简称SE)和龟裂链霉菌(Streptomyces rimosus简称SR)灭活原生质体和种间融合频率的影响.正交实验结果表明:在温度40℃,融合时间5min,聚乙二醇(PEG)浓度为40%的条件下,灭活原生质体融合频率为1.03×10^-5,在He-Ne激光与PEG双重促融作用下,双亲灭活原生质体的种间融合频率可达7.86×10^-5.证实了He-Ne激光对原生质体融合有明显的促进作用.     

Production of bioactive tryptamine derivatives by co-culture of marine Streptomyces with Bacillus mycoides

Tryptamine derivatives such as tryptamine and bacillamides were strong algicidal compounds promising in controlling harmful algae blooms, but their bioactivity and application researches were hindered by extremely low natural production rates. This study found an induced production of algicidal tryptamine derivatives by co-culture of marine Streptomyces with Bacillus mycoides, and optimised the culture method through changing important factors such as medium nutrition content, culture mode and pH value. The final established co-culture method used only 5 g yeast extracts and 5 g glycerol in 1 L 75% sea water, but got a yield of 14.9 mg/L N-acetyltryptamine, 2.8 mg/L N-propanoyltryptamine, 3.0 mg/L bacillamide A, 13.7 mg/L bacillamide B and 9.6 mg/L bacillamide C, which were all undetectable under normal culture conditions.     

Substrate requirements of phospholipase D from Streptomyces netropsis in the transphosphatidylation synthesis of phospolipids

The effect of the structure of the phospholipid substrate on the yield of phosphatidyl-5′-thymidine by transphosphatidylation catalyzed by phospholipase D from Streptomyces netropsis was studied. The reaction and product yield depended on the structures of the polar and nonpolar parts, the hydrophobic-hydrophilic balance, and the degree of unsaturation of the fatty-acids in the phospholipid substrate. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 26–29, January–February, 2006.     

Biologically active compounds from Lake Baikal streptomycetes

Data on the biological activity of ethylacetate extracts of Lake Baikal streptomycetes were obtained for the first time. The extracts of isolated actinobacteria of the genus Streptomyces were tested for the presence of compounds that inhibit the growth of pathogenic and conditionally pathogenic microorganisms and that exhibit a cytotoxic effect on Erlich carcinoma tumor cells. The ability of streptomycetes to produce inhibitors of enzymes isolated from marine organisms was also investigated. The production of bioactive compounds as a function of medium composition was given. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 65–69, January–February, 2006.     

Isolation and Structure Elucidation of Autolytimycin, A New Compound Produced by Streptomyces Autolyticus JX-47

In our previous studies on the actinomycete resources in Yunnan Province, we found some strains with potential bioactivities. Streptomyces autolyticus JX-47, a strain producing broad-spectrum antiviral metabolites was studied. A new compound autolytimycin 1, together with the other two known compounds, lebstatin 21 and 17-O-demethyl-geldanamycin 32,3, were isolated from the culture broth. The structure of autolytimycin was determined by spectral evidence, and shown to be similar to geldanam…