Isolation, distribution and evaluation of cytotoxic and antioxidant activity of cultivable actinobacteria from the Oman

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Isolation, distribution and evaluation of cytotoxic and antioxidant activity of cultivable actinobacteria from the Oman Sea sediments Mohsen Gozari1, 2*, Nima Bahador1, Amir Reza Jassbi3, Mohammad Seddiq Mortazavi2, Samad Hamzehei4, Ebrahim Eftekhar5 1 Department of Microbiology, College of Science, Agriculture and Modern Technology, Shiraz Branch, Islamic Azad

University, Shiraz 71331, Iran 2 Persian Gulf and Oman Sea Ecological Research Center, Iranian Fisheries Science Research Institute (IFSRI),

Agricultural Research, Education and Extension Organization (AREEO), Bandar Abbas 79131, Iran 3 Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz 71331,

Iran 4 Iranian National Institute of Oceanography and Atmospheric Science, Tehran 1414, Iran 5 Molecular Medicine Research Center, Hormozgan Health Institute, Hormozgan University of Medical Sciences,

Bandar Abbas 79131, Iran Received 17 December 2018; accepted 28 March 2019 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2019

Abstract

Screening bioactive natural products from bacteria is a determinative step in the drug discovery programs. The present study aim to isolate actinobacteria from the Oman Sea sediments for determining the effects of different culture media and treatments on the yield of the isolation process, and measure the DPPH radical scavenging and Artemia cytotoxic activity of culture extracts of the actinobacterial isolates. A total of 290 actinobacterial isolates were collected from 14 sediment samples. Heat treatment (40.68%) and M4 medium (29.31%) exhibited the maximum isolation rates of actinobacteria. Streptomyces isolates were dominantly distributed in all of the investigated stations according to 16S rRNA gene sequencing. The distribution pattern of Streptomyces followed a depth-dependent frequency trend, whereas the members of rare genera including Micromonospora, Nocardia Actinoplanes, Nocardiopsis, Saccharopolyspora and Crossiella were distributed in deeper stations. Approximately, 25% of the examined isolates could scavenge 90% of 10–4 mol/L DPPH solutions at 1 250 μg/mL final concentration of their ethyl acetate culture extracts. Furthermore, the most potent extracts could scavenge DPPH radicals with IC50 ranges from 356.8 to 566.4 μg/mL. Brine shrimp cytotoxicity tests showed that 38.88% of the examined culture extracts exhibited LC50 lower than 1 000 μg/mL against the Artemia cells. Moreover, the most potent culture extracts exhibited LC 50 range from 335.4 to 534.4 μg/mL. Phylogenetic analysis by 16S rRNA gene sequence revealed that the OS 005, OS 263 and OS 157 closely related to Streptomyces djakartensis, Streptomyces olivaceus and Nocardiopsis dassonvillei respectively. These results suggested the widespread distribution of the antioxidant and cytotoxic producing actinobacteria in the Oman Sea sediments, which could be considered as promising candidates for the discovery of microbial bioactive compounds. Key words: antioxidant activ