Intermolecular Interaction and Dissolution Rate of the Mixed Monolayers of 1-Monoglycerides and Cholesterol

Abstract

The surface pressure-mean area curves of the mixed monolayers of 1-monostearin and cholesterol as well as 1-monolaurin and cholesterol were measured. In the relation between mean area and mole fraction of cholesterol for both mixed monolayers, negative deviation from the additivity rule of mean area was found to be greatest at a mole fraction of cholesterol of 0.5. The dissolution rate of 1-monolaurin from the mixed monolayer of 1-monolaurin and cholesterol was obtained by measuring the rate of decrease in surface pressure at constant area. Surface pressure of the mixed monolayer, which had been compressed rapidly and held at the constant area, decreased linearly with the square root of elapsed time. The surface concentration of 1-mon olaurin corresponding to each surface pressure was calculated from the relation between mean area and mole fraction of cholesterol. Logarithm of surface concentration of 1-monolaurin varied linearly with the square root of elapsed time as in the monolayer of 1- monolaurin itself. The rate constant of the dissolution of 1-monolaurin decreased when the mole fraction of cholesterol exceeded 0.5.
It was concluded that the complex with one mole of 1-monoglyceride to one mole of cholesterol was formed in their mixed monolayer.