Quantitative retention-biological activity relationship study by micellar liquid chromatography.

In a previous paper, the usefulness of micellar liquid chromatography (MLC) in predicting octanol-water partition coefficients of organic compounds was reported. This paper is the first successful report of a quantitative retention-activity relationship study using the retention factor in MLC for predicting the biological activity of a group of phenolic compounds. Excellent correlation was obtained between the capacity factor in MLC and the bioactivity (measured as log 1/C, where C is the 50% inhibitory growth concentration) of 26 para-substituted phenols. A single MLC retention parameter is capable of describing the bioactivity of phenols, while three conventional molecular descriptors (log P(ow), pKa, and R) are needed to achieve a similar correlation. This indicates that both hydrophobic and electronic interactions are incorporated in a single MLC retention parameter, which is due to the amphiphilic nature of surfactants in the system. In situations like this, QRAR is a suitable alternative to QSAR since measuring MLC retention is much easier than measuring different molecular descriptors needed to build the QSAR model. Addition of 10% 2-propanol to a micellar system (hybrid system) proved to be the best chromatographic system for the best estimation of the phenols bioactivity. Other chromatographic factors such as pH and stationary phase also showed significant effect on the correlation between capacity factor k' and log 1/C.