الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Actinomycetes (actinobacteria) have been, for decades, one of the most important sources for the discovery of new antibiotics with an important number of drugs and analogs successfully introduced in the market and still used today in clinical practice.
In this investigation, 80 actinomycetes were isolated from different marine Egyptian habitats, including Hurgada sea, Ras Sedr sediment, Ain Sokhna sediment and that associated with marine algae.
1. Actinomycetes were isolated according to their special morphological characteristics, 80 actinomycetes isolates were isolated. Colonies of actinomycetes are usually round, convex, shaped colonies, with deeply rooting growth into the medium and covered with spore masses, they were dry and powdery. The isolate have been maintained on starch-nitrate agar slants.
2. The broth cultures of the 80 isolates were screened biologically for their antimicrobial activity against a wide range of test microorganisms comprising: Gram +ve bacteria; (Bacillus subtilis ATCC6633 and Staphylococcus aureus ATCC6538-P), Methicillin-resistant Staphylococcus aureus (MRSA) (ATCC25923) and Gram–ve bacteria (Escherichia coli ATCC14169 and Pseudomonas aeruginosa (ATCC27853), Klebsiella pneumoniaeCIP104216, yeasts: Candida albicans (ATCC10231), Candida albicans (ATCC9080) and fungus: Aspergillus niger (NRRL A-326).
3. The obtained results showed that, ten isolates were primarily selected as they exhibited interesting antimicrobial activities (AW2, AW6, 25W11, AR3, AR10, AR19, B2, B4, B7 and, B9) with a clear zone of inhibition against all the test microorganisms. Out of the ten isolates, two isolates (AW6 and 25W11) were the most potent as they exhibited pronounced antimicrobial activity.
4. The most potent strains (AW6 and 25W11) were subjected to identification using phenotypic and genotypic analysis.
5. To obtain the bioactive compounds of the two selected strains large-scale fermentation was carried out using rice media for cultivation.
6. For the biological evolution of the isolated pure compounds, the antimicrobial activity testing of compounds C1:C 5 using MTP assay revealed that all compounds had low antibacterial activity toward S. aureus and E. coli. While no pronounced activity has been detected toward the rest microbes including P. aeruginosa, C. albicans and A. niger.
7. The antioxidant activity of compounds (C1: C5) based on 2,2-diphenyl-1-picrylhydrazyl radical (DPPH assay; 200 µg/ml) revealed that 1-methoxy-3-methyl-8-hydroxy-anthraquinone (C2) was the most antioxidant agent, showed maximum DPPH scavenging activity (55.25 %), followed by umbelliferone )C1) (30.20 %). Also, the two compounds showed DPPH antioxidant activity with IC50 values of 5.47 and 3.84 µg/ml for C1 and C2, respectively
8. The obtained purified compounds C1 and C2 for their Gyr-B inhibitory activity. The two compounds showed inhibition of Gyr-B enzyme. Compound C1 was the most potent inhibitor, with an IC50 value of (3.79 ± 0.21 µM), while compound C2 was the least potent (IC50 = 13± 0.71µM).
9. The inhibition of Topoisomerase II by purified compounds was also measured.
10. The ADME-related physicochemical properties and cytotoxicity of Umbelliferone (C1) and 1-methoxy-3-methyl-8-hydroxy-anthraquinone (C2), 7-Methoxy-2, 3-Dimethylchromone-4-One (C3), 8-O Methyltetra-ngulol (C4), and 4-Ethoxybenzoate (C5) were estimated using SwissADME online server and protox ii.