The Structural Identification And Antitumor Activity On MCF-7 Cells Of Surfactin

Among various lipopeptides which are classified as biosurfactants produced by Bacillus sp.,surfactin is highlighted by researchers because of its powerful surface activity and broad bioactivities in other fields.In past years,many researches about lipopeptides mainly focused on its surface activity,however,there were few reports on its bioactivities, specially on antitumor activity.This thesis aimed at the study of Bacillus natto TK-1 screened out from Natto.The authors purified the lipopeptide using Thin-Layer Chromatography(TLC),and investigated its anti-tumor activity.After acid precipitation and methanol extraction,the lipopeptide was separated on TLC.Then the monomer surfactin was gotten which molecular weight was 1036D through the High Performance Liquid Chromatography(HPLC),electro spray ionization-mass spectrometry(ESI-MS) and infrared(IR).The antitumor activity of surfactin on MCF-7 cells was associated with cell apoptosis determined by typical morphological changes.MTT method was implied to test the anti-tumor activity of surfactin.The results indicated a concentration and time-dependent relationship between MCF-7 cells treated with surfactin or without.After 48h treatment,the IC₅₀ of surfactin was 38.77 mg/L.The detection with inverted microscope and fluorescence microscope displayed that the surfactin caused a series of morphological changes in cells.TUNEL experiment showed that surfactin had the ability to induce apoptosis,and this inhibition showed an obvious time-dependent relationship.The level of intracellular free calcium was significantly elevated by surfactin and showed a time-dependent manner,p53,Bcl-2 and Bax proteins were examined by Western blotting. Up-expression of p53,under-expression of Bcl-2 and increase of Bax:Bcl-2 ratio showed that Bcl-2 family proteins were involved in apoptosis.