from Streptomyces sp. KML-2, isolated

Background: Actinomycetes are gram positive bacteria with high G + C content in their DNA and are capable of producing variety of secondary metabolites. Many of these metabolites possess different biological activities and have the potential to be developed as therapeutic agents. The aim of the present study was to screen actinomy-cetes inhabiting halophilic environment such as Khewra salt mines present in Pakistan for cytotoxic and antitumor compounds. Results: An actiomycetes strain designated as Streptomyces sp. KML-2 was isolated from a saline soil of Khewra salt mines, Pakistan. The strain Streptomyces sp. KML-2 showed 84 % cytotoxic activity against larvae of Artemia salina. In the screening phase, the strain exhibited significant antitumor activity with IC50 values of 12, 48 and 56 µg/ml against Hela, MDBK and Vero cell lines, respectively. After that extract from 20 l fermentation was used to purify secondary metabolites by several chromatographic techniques. Structure elucidation of isolated compounds revealed that it is highly stable producer of Chromomycin SA (1) and 1-(1H-indol-3-yl)-propane-1,2,3-triol (2). Both of the isolated compounds showed significant antitumor activity against Hela and MCF-7 cancer cell lines (IC50 values 8.9 and 7.8 µg/ ml against Hela; 12.6 and 0.97 µg/ml against MCF-7, respectively). The 16S rRNA gene sequence (1437 bp) of the strain confirm its identity (99 %) with Streptomyces griseus