[Partition coefficients and Rm-values of cardenolides (author's transl)]

Partition coefficients (P) of 48 cardenolides were determined in octanol/water. Furthermore Rm-values of most of these substances were measured in different thin-layer chromatography systems (TLC) and related to P. Regression analysis revealed that the best linear fit of the data was obtained when Rm-values from reversed-phase TLC on octanol impregnated silica-gel layer as stationary phase and methanol/water as mobile phase were correlated with log P (r = 0.91). A better correlation between these two sets of data was obtained by restricting the calculations to groups of cardenolides with similar structural features (r = 0.96-0.98). The present results are showing that Rm-values from reversed-phase TLC--a rapid and reproducible method with many advantages over the tedious measurement of P--can be used to predict P.