Evaluation of antioxidant, antibacterial, and gas chromatography-mass spectrometry analysis of ethyl acetate extract of streptomyces omiyaensis SCH2

Abstract

Objective: The aim of this study was to evaluate the antibacterial and antioxidant properties of ethyl acetate extract of Streptomyces omiyaensis SCH2. The chemical constituents of the extract were investigated using gas chromatography-mass spectrometry (GC-MS). Methods: Secondary metabolites from S. omiyaensis were produced by submerge fermentation using ISP2 medium with 3% NaCl (w/v) for 21 days. The culture filtrate was extracted with ethyl acetate. The chemical constituents were detected in the GC-MS analysis. Antibacterial activity was performed using disc diffusion and broth microdilution methods. Antioxidant activity was evaluated by determining the reducing power capacity and free radical scavenging assays. Results: The GC-MS analysis of the SCH2 extract revealed the presence of four compounds. The main constituents were 2-phenylacetamide (79%). The extract exhibited the highest zone of inhibition against some pathogenic bacteria such as Enterobacter cloacae, Klebsiella pneumoniae, and Bacillus subtilis. In addition, the lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of extract were obtained for E. cloacae (0.125 and 4 mg/ml). The extract showed antioxidant potential with IC50 values of 2,078.13±24.58 µg/ml and 475.74±4.56 µg/ ml for 2,2-diphenyl-1-picryl-hydrazyl and 2,2′-azino-bis[3-ethylbenzothiazoline-6-sulphonic acid] assays, respectively. The ferric reducing antioxidant power value of extract was 110.36±1.75 mmol FeSO4.7H2O/g extract. Conclusion: This study indicated that S. omiyaensis extract possesses antibacterial and antioxidant activities. GC-MS analysis revealed the presence of major chemical constituents, acetamide, and pyrrolopyrazine which could be responsible for the biological activities. S. omiyaensis extract could be used as a potential of natural antibacterial and antioxidant agents for pharmaceutical and medical applications.