Antimicrobial, Antioxidant Activity of Ethyl Acetate Extract of Streptomyces sp. PERM2, its Potential Modes of Action and Bioactive Compounds

Background: Microorganisms belonging to Streptomyces sp. are Gram-positive bacteria known for their unsurpassed capacity for the production of secondary metabolites with diverse biological activities. The aim of this study was to evaluate the antimicrobial and antioxidant properties of ethyl acetate Streptomyces sp. PERM2 extract, its potential modes of action and bioactive secondary metabolites. Results: The ethyl acetate PERM2 extract showed antimicrobial activity more pronounced on both Gram-positive and Gram-negative bacteria and fungi with a Minimum Inhibitory Concentration value (MIC) of 0.5 mg/mL and Minimum Bactericidal Concentration (MBC) of 2 - 4 mg/mL against bacterial pathogens. MIC value against pathogenic fungi was 2 mg/mL and Minimum Fungicidal Concentration (MFC) of 0.01 - 0.05 mg/mL against pathogenic fungi. PERM2 crude extract showed the ability to inhibit bacteria cell wall synthesis at 0.5 and 1 MIC. The extract was found to possess dose-dependent 2,2-Diphenyl-picrylhadrazyl (DPPH) free radical scavenging and Ferric reducing activity. The gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of three major compounds identified as 9,12-octadecadienoic acid (Z, Z) (29.75%), tridecyl trifluoroacetate (24.82%) and 1-(+)-ascorbic acid 2, 6-dihexadecanoate (22.34%). The liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed the presence of 22 non-volatile metabolites in PERM2 extract and only the compound 3, 30-O-dimethylellagic acid was identified. Conclusion: The results of this study indicate that ethyl acetate Streptomyces sp. PERM2 extract possesses antibacterial, antifungal, and antioxidant activities; inhibits bacteria cell wall and protein synthesis; and contains significant bioactive secondary metabolites which could be used as an alternative to multi-resistance antibiotics.