Isolation and Evaluation of Cytotoxic and Antioxidant activity of the isolated Actinobacteria from the Two Species of Persian Gulf Sea Cucumber

Marine actinobacteria are the prolific sources of marine natural products. The aims of the present study were to propose a process for selective isolation of actinobacteria from the two species of sea cucumbers and to find isolates that produce antioxidant and cytotoxic metabolites. We collected 2 sea cucumbers species from the Larak Island, Persian Gulf using scuba diving. The selective isolation process was performed by 3 culture media and 7 physical and chemical treatments. Antioxidant activity of extracted metabolites were evaluated using DPPH radical scavenging activity. Evaluation of cytotoxicity of the extracted metabolites was carry out using brine-shrimp microwell cytotoxicity assay. Out of 53 actinobacterial isolates, 58.49% was isolated from sea cucumber H. leucospilota. Starch casein nitrate agar medium exhibited maximum efficiency and isolated 22 isolate of actinobacteria.  Heat treatment isolated 39.62% of actinobacterial isolates and recovered their most frequency. Approximately, 37.03 % of the extracted metabolites scavenged more than 90% of the DPPH radicals and their IC50 ranges from 136.1 to 641.5 µg/ml. While, 33.33 % of the extracted metabolites were able to kill more than 90% of the Artemia cells at LC50 range from 118.12 to 653.15 µg/ml. These results represented a selective isolation process for sea cucumber associated-actinobacteria and also could provide an evidence that confirms the active association of the actinobacteria with the Persian Gulf sea cucumber species.