ABSTRACT
310 311In an ongoing survey for the bioactive potential of microorganisms isolated from soil and dung samples collected from the biodiversity hotspot, the Kaziranga National Park, Assam, India, an Aspergillus turcosus strain Kaziranga-131 (KZR131) was isolated from forest soil, exhibiting broad spectrum antimicrobial, antifeedant, and insecticidal activities. Bioactivity- guided purification resulted in the isolation of two compounds. Based on 1H and 13C NMR, Fourier transform infrared spectrum (FT-IR), and mass spectroscopic techniques, the chemical structures were elucidated as gliotoxin and acetylgliotoxin. The crystal structure for acetylgliotoxin has been established for the first time with the accession number Cambridge Crystallographic Data Center (CCDC) 1054601. Gliotoxin and acetylgliotoxin exhibited a broad spectrum antimicrobial activity against Gram- positive and Gram negative bacteria, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE), and different Candida strains. Gliotoxin showed a dose-dependent antifeedant activity of 76.4% against Spodoptera litura and 66.4% against Achaea janata, respectively,50 at 60 μg cm−2 area of castor leaf. The LC (50% lethal concentration) values of gliotoxin on S. oryzae, T. casteneum, and C. chinensis after 96 h were 5.52, 3.57, and 4.25, respectively. However, acetylgliotoxin did not exhibit antifeedant and insecticidal properties. To our knowledge, this is the first report on extrolites produced by Aspergillus turcosus strain KZR131 exhibiting broad spectrum antimicrobial activity, and promising antifeedant and insecticidal activities against several agriculturally important pests.
