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.