Myxobacteria are unique gram-negative bacteria characterized by the gliding and fruiting body forming nature. They have recently been well established as a new and potent source for natural products with biological activities because of their potential to produce a considerable variety of metabolites.1-4) Thus, myxobacteria especially attract many researchers, since they have many possibilities of producing undiscovered bioactive substances.5) They are not obtained by the routine method used in culturing bacteria and thus require special techniques for their isolation and culture. We established in these techniques about Sorangium cellulosum in Korea.
In our search for the bioactive metabolites from myxobacteria, strains KM1001 and KM1041 of Sorangium cellulosum, were found to produce potent bioactive compounds. They were isolated and purified by silica gel column chromatography and semi-preparative HPLC. The structures of these compounds were determined on the basis of combined spectroscopic analysis.
Epothilone A (1)6-8) from S. cellulosum KM1041 shown to have a significant cytotoxicity against the HM7 and HeLa human cancer cell lines with IC50 values 20 and 30nM. At higher concentrations of epothilon A, the microtubles became arranged in bundle-like formations at the periphery of the cell.9-13) The major component from S. cellulosum KM1001, named soraphinol C(4)14-16) was found to be a new compound closely related to the minor component, 4-hydroxysattabacin (5).17) Soraphinol C (4) showed antioxidant activity comparable to that of Trolox, while 4-hydroxylsattabacin (5) possessed only a weak antioxidant activity.