In the course of our screening program for new bioactive compounds from our natural product library,1 a number of ‘talented’ strains were discovered based on their bioactivity spectrum or novel peaks on liquid chromatography-diode array detection-mass spectrometry (LC-DAD-MS) analysis. A Streptomyces sp. LS1924 strain was found to have the ability to produce bioactive metabolites and was selected to be studied further leading to the discovery of LS1924A (1), a new analog of emycins, together with three known compounds of angucyclinone family. In this paper, we report the fermentation, isolation, chemical characterization of these compounds and the bioactivity of the new compound.

The producing strain Streptomyces sp. LS1924 was isolated from a soil sample collected from Yaoli Virgin Forest (elevation 850 m) of Jiangxi Province, China. Strain LS1924 was deposited at the China General Microbiological Culture Collection Center (CGMCC) with the accession number CGMCC No.5240. The strain was grown and maintained on a GT-medium agar slant consisting of soluble starch 2.0%, L-asparagine 0.05%, KNO3 0.1%, K2HPO4·H2O 0.05%, NaCl 0.05% and MgSO4·7H2O 0.05% (pH 7.5) at 28 °C. The stock culture was transferred into 250-ml Erlenmeyer flasks containing 40 ml of the seed medium with the same components as the agar slant medium. The culture was incubated on a rotary shaker (220 r.p.m.) at 28 °C for 4 days. Ten milliliters of the seed culture was transferred to 1000-ml Erlenmeyer flasks containing 250 ml of the producing medium, which contains glucose 1.0%, millet meal 2.0%, cottonseed protein powder 2.0% and MOPS 2.0% (pH 7.0). The fermentation broth was incubated at 28 °C for 8 days on a rotary shaker at 220 r.p.m.

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