Z-axinohydantoin and debromo-z-axinohydantoin from the sponge Stylotella aurantium: Inhibitors of protein kinase C

During the large scale isolation of the hymenialdisine and debromohymenialdisine, potent inhibitors of PKC, from Stylotella aurantium, we also isolated several related minor metabolites, two of which proved to be novel. The structures of these new compounds, Z-axinohydantoin (1) and debromo-Z-axinohydantoin (2), were determined by interpretation of spectral data. Z-axinohydantoin (1) and debromo-Z-axinohydantoin (2), were found to be inhibitors of PKC with IC50 values of 9.0 and 22 mu m respectively.