Antimicrobial and antioxidant properties of marine actinomycetes Streptomyces sp VITSTK7

Abstract

Mohankumar Thenmozhi, Krishnan Kannabiran

Abstract Marine actinomycetes are potential provider of novel bioactive metabolites and currently emerged as an important source for natural products with unique chemical diversity. The aim of the present study was to evaluate antimicrobial and antioxidant potential of the actinomycetes isolate Streptomyces sp VITSTK7 isolated from marine sediments collected at the Bay of Bengal coast of Puducherry, India. The culturing conditions such as pH, temperature, NaCl, carbon source and nitrogen source were optimized for maximal growth by dry weight method. The ethyl acetate (EA) extract showed a significant antifungal activity against Aspergillus fumigatus with the MIC value of 0.25 mg/ml. However, EA extract showed moderate antibacterial activity against selected bacterial pathogens. The antioxidant potential of the extract was assessed by DPPH• (1,1-Diphenyl-2-picrylhydrazyl) scavenging activity, Fe+3 reducing assay, metal chelating assay and DNA inhibition protection assay. The DPPH• scavenging activity was 43.2% at 10 mg/ml of EA extract and compared with ascorbic acid standard. The Fe+3 reducing assay showed 0.37 absorbance at 700 nm at 10 mg/ml of EA extract. The EA extract at 10 mg/ml showed 51% metal chelation. The ability of EA extract to protect DNA (pBR322) against UV-induced photolysed H2O2-oxidative damage was also analyzed. The EA extract was able to protect the DNA significantly from oxidative damage. The results of this study indicate that the ethyl acetate extract of the isolate possess both free-radical scavenging and antimicrobial activity.

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