الفهرس 
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Abstract
Summary:
Twenty five actinobacterial isolates were recovered from the rhizosphere soil of mangrove trees (Avicennia marina) in Marsa-Allam. The isolates were investigated for potential antimicrobial activity against five tested pathogens. Four isolates were selected, they exhibit antimicrobial activity against Gram positive, Gram negative and Candida albicans. Isolates were identified by conventional methods and 16S rRNA gene sequencing as: Streptomyces atrovirens (MS5), Streptomyces labedae (MR15), Streptomyces rochei (MM23) and Streptomyces sampsonii (RR12). The isolates were fermented in starch casein broth medium and cell free extract were prepared using ethyl acetate as a solvent. The ethyl acetate extract was tested against pathogens using well diffusion method to investigate the MIC values. The MIC values of the ethyl acetate extract of Streptomyces atrovirens (MS5) were 3x103, 5 x103, 1 x104 μg/ml against E.coli, Bacillus cereus and Candida albicans respectively, The MIC values of the ethyl acetate extract of Streptomyces labedae (MR15) and Streptomyces sampsonii (RR12) were 500 μg/ml against Staphylococcus aureus and Candida albicans and E.coli. The MIC values of the ethyl acetate value of Streptomyces rochei (MM23) against Pseudomonas aeruginosa was 250 μg/ml. DPPH assay was applied on the ethyl acetate extracts of the four isolates and showed radical scavenging activity percentages of 62, 78, 80, 65% at 5000, 2000, 5000, 500 µg/ml with IC50 values of 3000, 241, <50 and 78 µg/ml respectively. Streptomyces atrovirens (MS5) extract showed anticancer activity against hepatocellular carcinoma cells (HepG-2) and colon carcinoma cells (HCT-116) cell lines with 61% and 50.6%, respectively, while Streptomyces rochei (MM23) and Streptomyces sampsonii (RR12) showed anticancer activity against all the tested cell lines in comparison with the control cells. LC mass/MS technique revealed that the two ethyl acetate crude extracts have major bioactive compounds are present in high intensities like Gamma Aminobutyric acid (GABA), Indole-3-carboxyaldehyde, DL-Pipecolinic acid and minor bioactive compounds are present in low intensities like loliolide, linalool and tyramine. Major compounds are found in the ethyl acetate crude extract of MR15 were 4-hydroxy-3-(3-methyl-2-butenyl) acetophenone, linoleic acid, 4-methylumbelliferone and phenyl chromene-4-dervitative and minor bioactive compounds like 3-Indoleacetic acid and 2-phenylethyl acetamide.