Water as a nonpolar partition medium

Area of Science:

• Biophysical Chemistry
• Pharmacokinetics
• Materials Science

Background:

• Cytoplasm, an aqueous phase of water-protein-colloid complexes, has been modeled using coacervates.
• Understanding drug partitioning is crucial for predicting absorption and efficacy.

Purpose of the Study:

• To evaluate coacervate systems as nonpolar phases for determining partition coefficients.
• To correlate coacervate partition coefficients with established organic solvent systems and in vivo drug absorption data.

Main Methods:

• Coacervate phases were used as nonpolar media in equilibrium with polar water phases.
• Partition coefficients of four barbiturates were measured.
• Partition coefficients of theobromine and theophylline were determined in gelatin-benzalkonium chloride coacervate systems.

Main Results:

• Partition coefficients obtained using coacervates correlated well with those from conventional organic solvent-water systems.
• Coacervate partition coefficients also correlated with reported barbiturate absorption rankings in rat colon.
• Theobromine and theophylline partition coefficients in coacervates correlated with literature values for heptane-water and chloroform-water systems.

Conclusions:

• Coacervate systems provide a more realistic model for studying drug partitioning compared to traditional organic solvent systems.
• This approach can enhance the prediction of drug absorption characteristics.