Isolation and characterization of novel endogenous digitalis-like factors in the ovary of the giant toad, Bufo marinus

We have previously described the structures of four novel unconjugated bufa dienolides in the ovary of the toad, Bufo marinus. In this study, we report the separation and characterization of three novel bufadienolide conjugate s. These compounds were purified by HPLC, and their structures were determi ned to be 11 alpha, 19-dihydroxytelocinobufagin-3-(12-hydroxydodecanoic aci d) ester, 11 alpha, 19-dihydroxytelocinobufagin-3-(14-hydroxy-7-tetradeceno ic acid) ester, and 11 alpha,19-dihydroxytelocinobufagin-3-(14-hydroxytetra decanoic acid) ester on the basis of NMR and MS data. Numerous dicarboxylic acid esters of bufadienolides have previously been described, but the thre e bufadienolide conjugates described in this report differ from previously described esters in that they contain hydroxylated monocarboxylic acids. Th e function of these three conjugates is not known but they are, like bufoto xins, potent inhibitors of Na+,K+-ATPase and may play a developmental role in the differentiation of toad oocytes.