ABSTRACT
Free radicals produced through biochemical processes cause dangerous health problems due to their oxidative effect on cellular proteins and lipids. There is an urgent need for natural antioxidants to be used as therapeutic agents. Streptomyces are known as producers for antioxidants, in this study, two Streptomyces species were isolated from the rhizosphere soil of mangrove tree Avicennia marina (Forssk.) Vierh. The isolates were identified by conventional as well as molecular methods as Streptomyces atrovirens (MS5) and S. labedae (MR15). The ethyl acetate extracts of cell free production broth medium of the two isolates demonstrated potent biological activities against Gram positive and Gram negative bacteria and Candida albicans. Moreover, a radical scavenging activity in DPPH assay with significant inhibition percentage of 62 and 78%, respectively, was recorded. The IC50 values were 3000 and 241 ?g/mL (P <0.05) for S.atrovirens (MS5) and S. labedae (MR15), respectively. Streptomyces atrovirens 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 S. labedae (MR15) showed anticancer activity against all the tested cell lines with 92.9 and 85.89% against (HepG-2) and (HCT-116) compared to the control cells and showed selective cytotoxicity. LC-MS/MS analyses revealed the presence of compounds with known antioxidant and anticancer activities such as Gamma Aminobutyric acid (GABA) and Indole-3-carboxyaldehyde, linoleic acid and phenyl chromen-4-one derivative with various intensities.
ABSTRACT
A distinct strain named Micromonospora sp. Rc5 was isolated from Sinai desert of Egypt and recorded high antagonistic activities against some food and bloodborne pathogens. Morphological and chemotaxonomy characterization confirmed that this isolate belongs to genus Micromonospora. Sequencing of partial 16S rDNA and BLASTN showed that isolate Rc5 is identical to Micromonospora haikouensis (99%) but with low bootstrap value in NJ phylogenetic tree. Comprehensive optimization of several growth factors was performed including initial pH, incubation periods, and different sources of carbon and nitrogen. The highest yield of antimicrobial agent production was obtained after 8 days of incubation at 30°C, pH 6.0, 3 x 105CFU/ml in soya bean meal broth media with agitation of 150 rpm. A dramatic proportional decrease occurred with 0.3, 0.6, 0.9 µg active fraction /ml against Staphylococcus aureus culture and reached to complete inhibition at a minimum inhibitory concentration of (1.5 µg /ml). The physicochemical characterization of the purified fraction was identified as phthalate derivative. Our results indicated that Rc5 generated potential antimicrobial compounds against foodborne pathogens and may combat resistant strains of Staphylococcus aureus.