QUANTITATIVE STRUCTURE-CHROMATOGRAPHIC RETENTION RELATIONSHIP STUDY OF 6 UNDERIVATIZED EQUINE ESTROGENS

Underivatized estrone (ES), equilin (EQ), equilenin (EQN) and their co rresponding 17 alpha-diols 17 alpha-estradiol (ESD), 17 alpha-dihydroe quilin (DHEQ) and 17 alpha-dihydroequilenin (DHEQN) were separated by TLC, RP-HPLC and capillary GC. Their dipole moments (mu) and Randic's connectivity indices (1 chi) were determined as parameters of importan ce for the separation. The number of H atoms was taken as an additive structural parameter of importance for the quantitative structure-chro matographic retention relationship study (QSRR). Principal component a nalysis (PCA) was applied in order to find similarities and dissimilar ities between 9 TLC and 10 RP-HPLC systems. PCA indicated that proton donor-proton acceptor interactions play the most important role for th e TLC and RP-HPLC separation. The two-dimensional non-linear map of PC variables showed that the keto-estrogens (ES, EQ and EQN) and the cor responding diols (ESD, DHEQ and DHEQN) form two separate clusters. The relationship between GC retention of equine estrogens characterized b y Kovats indices (KI), their (1) chi and mu was expressed by the equat ion KI/100=a/(1) chi+b/mu(2)+c. The biological activity of the estroge ns was related to log 1 mu(2).