Quantitative structure–property relationships (QSPR) for steroidal compounds of environmental importance

A quantitative structure–property relationships (QSPR) study was carried out for 17 steroidal compounds using calculated molecular descriptors and measured properties. The utility of calculated molecular descriptors and properties was evaluated and improved in some instances by subgroup classification of these 17 compounds into estrogens and androgens. The calculated values for the octanol–water partition coefficient (log Kow) were found to be in good agreement with the measured values for all 17 compounds, whilst good agreement between the calculated and measured values for aqueous solubility (log S) was found only for the subgroup of androgens. Good linear relationships (R2 ⩾ 0.782) were found between measured log Kow values and three molecular descriptors (log FOSA, hydrophobic component of the total solvent accessible surface area; log FISA, hydrophilic component of the total solvent accessible area and log PSA, Van de Waals surface area of polar nitrogen and oxygen atoms). For the measured log S values, only weak correlations with molecular descriptors were observed (R2 ⩾ 0.505). The coefficient of log S in the relationship with the hydrophobic parameter (log FOSA) was negative but positive with the hydrophilic parameters (log FISA and log PSA). Conversely with log Kow the opposite was found. These observations are in accord with the effects of molecular polarity on aqueous solubility.