Abstract: In order to screen strains which can produce secondary metabolites of inhibition of tumor growth,and isolate and identify active compounds,cholesterol was used as the sole source of carbon to screen strains from soil.The active components of the strain S823 were separated by chromatography and structure of them was identified by spectrum analysis.The strain was determinated according to morphology,physiological and biochemical characteristics,and 16 s rRNA gene sequence homology analysis.The test results showed that the strain extract could inhibit Neuro-2 a cell (mice glioma cells) growth.The compound was isolated by column chromatography and its structure was identified as prodigiosin base on analysis of MS and ¹H-NMR and ¹³C NMR.The strain S823 was analyzed by morphological observation,physiological and biochemical characteristics,and 16S rRNA sequence analysis.GenBank No.is KR817904.1.The similarity of it is 99% to Serratia marcescens.The inhibition rate of prodigiosin against cell cycle protein 25 B (CDC25B) was 67.7±2.9%,the inhibition rate was 56.7±0.4% against the protein tyrosine phosphatase containing structure domain of SH2 (SHP2).It has the inhibition effect on the Neuro-2 a cells,the value of IC₅₀ was 0.05 μM

Key words: biotransformation, antitumor activity, Serratia marcescans, 7β-hydroxycholesterol, prodigiosin