S-15183a and b, new sphingosine kinase inhibitors, produced by a fungus.

In the course of our screening for inhibitors of sphingosine kinase, we found two active compounds in a culture broth of a fungus, Zopfiella inermis SANK 15183. The structures of the compounds, named S-15183a and b, were elucidated by a combination of spectroscopic analyses to be new azaphilone-type metabolites. S-15183a and b inhibited sphingosine kinase from rat liver with IC50 values of 2.5 and 1.6 microM, respectively. S-15183a also inhibited endogenous SPH kinase activity in intact platelets.