Studies on antimicrobial metabolites from endophytic actinobacteria isolated from Pinus roxburghii of Pauri Garhwal region

Abstract

Study was conducted to isolate endophytic actinobacteria from Pinus roxburghii of Pauri region and tested for their antagonistic activity against human pathogens Total 88 plant samples were collected from Kotdwar to Pauri to Devpryag A total of 283 isolates were recovered and maximum obtained from root followed by needle and stem Morphological cultural characteristics and microscopic studies revealed that isolates belonged to Streptomyces Actinomadura Microbiospora Micromonospora Kitastaosporia Streptosporangium and Nocardia It was found that 135 and 42 isolates showed antibacterial and antifungal activity against one or more test pathogen respectively Only seven isolates displayed broad spectrum activity Isolate GBTPR113 and GBTPR137 were selected for further study and identified as Streptomyces sp In shake flask fermentation study starch casein broth was found to be best media and selected for production Further cultural conditions for maximizing the production were optimized by using one factor at a time approach For extraction of the produced antibacterial compounds they were absorbed on resin and eluted with methanol The bioactive compounds were separated and partially purified with preparative TLC and column chromatography The bioactive fraction of both the isolate displayed substantial antibacterial activity against all pathogens and also against drug resistant pathogens The partially purified compound was characterized by UV IR and LCMS LCMS analysis led to the identification of compounds as 5 7 4 trimethoxy flavone 2hydroxy 4 6 dimethoxy 3 methyl dihydrochalcone Grandiflorone Deoxycholic acid Ursodeoxycholic acid Chenodeoxycholic acid Artocarpin Melleolide M and Stigmatellin Y from Streptomyces sp GBTPR113 While Nordihydrocapsaicin Cocaine Anisocoumarin H Senecionine and Deoxycholic acid Ursodeoxycholic acid Chenodeoxycholic acid were identified from Streptomyces sp GBTPR137 The study suggested that unexplored niches could be potential source for exploring bioactive actinobacterial secondary metabolites