Purification and Structure Elucidation of Potential Cytotoxic Agents from Streptomyces parvus KJ623765

Abstract

Fermentation of Streptomyces (S.) parvus (accession code KJ623765), a locally isolated Streptomyces strains from Egyptian soil sample, was carried out in a 14 L laboratory fermentor. The optimum fermentation conditions were; incubation temperature, 28°C, agitation, 200 rpm, aeration, 5 standard liters per minute (SLPM), 2 bar airflow pressure, uncontrolled pH. After 72 h, the cell-free culture supernatant (CFCS) was collected and extracted using ethyl acetate (1:1, v/v) at pH 7.0. The crude extract showed potential cytotoxic activities against Caco2 and HeLa cancer cell lines with CD₅₀ of 3.4 and 6.8 µg/ml, respectively. Bioassay guided fractionation had led to the purification of compounds FF1 (12 mg), FGH4 (35 mg) and FGH5 (42 mg) per liter of the CFCS. Based on mass, 1D and 2D NMR spectroscopic analysis, they were identified as thymidine, diadzein and genistein, respectively. Production improvement was done using gamma radiation, where fourteen mutants showed marked increase in cytotoxic activity that reached 9.4 fold increase with mutants P43 and P59. Accordingly, S. parvus KJ623765 can be used as an industrial isolate for the commercial production of important cytotoxic metabolites. It is the first report about production of these anti-proliferative metabolites by the respective isolate.