Isolation and evaluation of cytotoxic and antioxidant activity of bioactive metabolites of cultured actinobacteria in Persian Gulf marine sediments

Screening bacteria for bioactive compounds is the first step in the drug discovery programs. The aim of the present research was to achieve cytotoxic and antioxidant metabolites from actinobacteria of Persian Gulf sediments and to investigate the effects of combinations of seven treatments and six isolation media on the selective isolation process. A total of 395 actinobacterial isolates were collected from 12 sediment samples. Heat treatment and M6 medium were exhibited maximum efficiency of 34.59% and 32.82% isolation, respectively. Preliminary characterization results revealed the dominant distribution of Streptomyces like isolates in all investigated stations. Streptomyces isolates distribution followed a depth dependent frequency pattern. Approximately, 27.45% of the examined isolates could scavenge 90% of DPPH radicals in 1250 µg/ml final concentration. Exudated metabolites of potent isolates could scavenge DPPH radicals with IC50 ranges from 411 to 670 µg/ml. The results of cytotoxic activity showed that 54.9% of examined isolates exhibited LC50 lower than 1000µg/mL against Artemia cells. Extracted metabolites from 12 potent isolates exhibited LC50 range from 236.3 to 565.3 µg/ml. These results suggest the widespread distribution of the antioxidant and cytotoxic producing actinobacteria in Persian Gulf sediments and represent actinobacterial isolates as promising candidates for the discovery of microbial derived bioactive compounds.