Selective Isolation of the Persian Gulf Sponge-associated Actinobacteria and Evaluation of Cytotoxic and Antioxidant activity of Their Metabolites

Sponge-associated actinobacteria are the prolific sources of marine natural products. The aims of the present study were to propose a process for selective isolation of sponge-associated actinobacteria and to find isolates that produce antioxidant and cytotoxic metabolites. We collected 4 sponge species from the Larak Island, Persian Gulf using scuba diving. The selective isolation process was performed by 4 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 114 actinobacterial isolates, 38.59% was isolated from sponge Dysedia avara. Marine sponge agar medium exhibited maximum efficiency and isolated 44 isolate of actinobacteria. While, most non streptomyces-like isolates were derived by marine zobell agar.  Heat treatment isolated 35.08% of actinobacterial isolates and recovered their most frequency. Approximately, 46 % of the extracted metabolites scavenged more than 90% of the DPPH radicals and their IC50 ranges from 230.1 to 775.34 µg/ml. While, 44% of the extracted metabolites were able to kill more than 90% of the Artemia cells at LC50 range from 236.3 to 565.3 µg/ml. These results represented a selective isolation process for sponge associated-actinobacteria and also could provide an evidence that confirms the active association of the actinobacteria with the Persian Gulf sponges.