[Isolation, purification and characterization of antifungal substances from Streptomyces hygroscopicus BS-112]

Objective: In order to provide the basis for application of Streptomyces hygroscopicus BS-112 and its Antifungal active substances, we isolated and purified the active substances produced by strain BS-112, and then we examined their chemical structures and determined their inhibitory effects on Aspergillus flavus.

Methods: We extracted and purified the Antifungal active substances from strain BS-112 using column chromatography with X-5 macroporous resin and 200 - 300 mesh silica gel respectively, and then purified them by preparative HPLC with Venusil XBP C18 column. The chemical structures of active components were identified by means of spectroscopic analysis, including mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR). Their minimum inhibitory concentration and minimum fungicidal concentration against Aspergillus flavus were determined by the standard broth microdilution method.

Results: We obtained four active components from the fermentation broth of strain BS-112 and their chemical structures were the same as Tetrins A and B, Tetramycins A and B. Assay using 96-well plate illustrated that the MIC of Tetrin A, Tetrin B, Tetramycin A and Tetramycin B against Aspergillus flavus were 3.13 microg/mL,12.56 microg/mL,1.56 microg/mL and 6.25 microg/mL respectively, and their MFC were 6.25 microg/mL, 25.0 microg/mL, 3.13 microg/mL and 12.56 microg/mL respectively.

Conclusion: The Antifungal active substances of strain BS-112 were composed of four compounds, Tetrins A and B, Tetramycins A and B. The four active compounds showed strong inhibitory against Aspergillus flavus.