SECONDARY METABOLITES OF ACTINOMYCETES AND THEIR ACTIVITY AGAINST PSEUDOMONAS AERUGINOSA
European Journal of Molecular & Clinical Medicine,
2020, Volume 7, Issue 10, Pages 4423-4434
AbstractActinomycetes are widespread in ecosystem and they are of interest in research field as they are capable to produce bioactive secondary metabolites which canbe developed into useful pharmaceutical products. The potential of antibacterial activity of derived actinomycetes from the genus Streptomyces were studied. The actinomycetes were identified as putative Streptomyces spp. and 4 strains were selected. Selected putative strains of Streptomyces spp. for bioactivity screening on inorganic salts starch agar (ISP4) for strains T3 and T4 and sporulation agar (SA) for the remaining strains. Inorganic salts-starch agar (ISP4) showed grey coloured spores and sporulation agar (SA) showed White/Brown spores.In primary screening, nine strains showed antagonistic activity against at least one test pathogenic bacteria. In secondary screening, all strains showed antagonistic activity against at least one test pathogenic bacteria. The culture filtrate extracted with ethyl acetate by adjusting the pH to 3 prior to extraction process resulted in maximum recovery of antimicrobial metabolites. The ethyl acetate crude extract obtained from the TC1 fermentation broth exhibited a MIC value of 300 μg/mL and IC 50 value of 125 μg/mL against the test pathogen P.aeruginosa.The culture filtrate and crude extract of Streptomyces sp. TC1 showed antimicrobial activity against various isolates of P.aeruginosa.Thin layer chromatographic separation of ethyl acetate crude extract of Streptomyces sp. TC1 resulted in nine bands with closer Rf values using chloroform: methanol (24:1 v/v) as the mobile phase. Consequently antimicrobial compounds were purified using column chromatography. Bioactivity guided column chromatographic separation of ethyl acetate crude extract afforded 27 different fractions using n-hexane-chloroform as a mobile phase. Among 27 different fractions, four fractions showed antimicrobial activity against Xoo by producing an inhibition zone of 1.9- 2.5 cm in agar well diffusion assay. The fraction F4 exhibited higher antimicrobial activity of 2.5 cm followed by F15, F9 and F22 which produced inhibition zone of 2.3, 2.0 and 1.9 cm respectively.The isolated antimicrobial metabolites including three novel compounds viz., 2- Clavulanic acid (compound 1) and 2-(1,1-diallyl-but-3-enyl)-5-nonyl-phenol (compound 2).
Keywords: Pseudomonas, Cetrimide agar, Actinomycetes, Streptomyces, MIC, Opportunistic Pathogen.
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