Abstract
Background:The Streptomyces are considered the most important bacterial source for bioactive compounds production including natural antibiotics. 
 Objective: This study focused on analysis of these products to characterize the most active substances which may contain new antibiotics. 
 Materials and methods: Samples with the highest antibacterial activities (21, M5, N- and D-) were chosen from a previous study after secondary screening for the intracellular (biomass) extract which showed more antagonism efficiency than that observed in extracellular crude extract.Gas chromatography – mass spectroscopy (GC-MS) was preformed to detect the structure of the compounds in intracellular crude extracts in these isolates. 
 Results: The GC-MS analysis showed a total of 49 peaks observed in 4 isolates, isolate M5=14 peaks, isolate D=11peaks, isolate N= 20 peaks and isolate 21= 4peaks. Isolate D-, which showed the highest zone of inhibition in secondary screening than that in other isolates, is associated with the most prevalence active compounds like the Decane derivatives, in addition to Triadimenol; Azetidine, 1-(1,1-dimethylethyl)-3-methyl; Hexanoic acid, 2-ethyl-, 2-ethylhexyl ester and 3,3,7,7-Tetramethyl-1,5-diazabicyclo(3.3.0)octane. While isolate 21, has less peaks in comparing with the other samples, with great occurrence in components: 1-Dimethylaminohexane with molecular formula C8H19N and molecular weight 129 and Propamocarb with molecular formula C9H20N2O2 and molecular weight 188, in addition to many volatile organic compounds. The greatest components of isolate M5 were Triadimenol and 3,3,7,7-Tetramethyl-1,5-diazabicyclo(3.3.0)octane, in addition to the presence of Decane derivatives; amine compounds and Vitamin E. Isolate N- showed a great occurrence with components Triadimenol and Azetidine, 1-(1,1-dimethylethyl)-3-methyl-with a molecular formula C8H17N and with a molecular weight 127; also the presence of an important component Hexanoic acid, 2-methyl- with the molecular formula C7H14O2 and with molecular weight 103 which has been considered as an essential component of muramycin antibiotic; compounds which contain Benzene ring. 
 Conclusion: The most prominent compounds detected in the selected isolates by using GC-MS technique were Decane derivatives and Triadimenol.
Highlights
Evaluation and characterization of these bioactive compounds determined by many methods like High Performance Liquid Chromatography (HPLC), Nuclear Magnetic Resonance spectroscopy (NMR) and Gas Chromatography Mass Spectroscopy (GC-MS) [7]
Mass spectrum of GC-MS was interpreted according to the National Institute Standard and Technology (NIST) database, by comparing the spectrum unknown with the known data stored in NIST library
In addition to Triadimenol, it is a fungicide with molecular formula C14H18ClN3O2 and molecular weight 295, was reported by [18]
Summary
Actinomycetes constitute a significant component of the microbial population in most soils and the most important member of the actinomycetes is the genus Streptomyces which accounts for 80% of the total Actinomycetes population [1]. The genus Streptomyces is aerobic and spore forming Actinomycetes and recognized as highly producing of useful bioactive metabolites with broad spectrum activities, such as antibacterial, antifungal, antibiotic, antiparasitic, antitumor and antiviral, immunomodulators agents [2,3] They form approximately 80% of the total antibiotic products as compared to other actinomycetes genera and considered to be the major source of bioactive secondary metabolites and antibiotics producer, forming more than half of the naturally produced antibiotics [3,4]. Isolate N- showed a great occurrence with components Triadimenol and Azetidine, 1-(1,1-dimethylethyl)-3-methyl-with a molecular formula C8H17N and with a molecular weight 127; the presence of an important component Hexanoic acid, 2-methyl- with the molecular formula C7H14O2 and with molecular weight 103 which has been considered as an essential component of muramycin antibiotic; compounds which contain Benzene ring.
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