Cholesterol Monohydrate Dissolution in Bile Salt‐Lecithin Solutions

Abstract

A modified dissolution rate equation was used to quantitatively investigate the contribution of simple bile salt (BS) micelles and mixed BS-lecithin (L) micelles to a cholesterol monohydrate (ChM) dissolution. Using a least-squares technique to assess the relationship between the ChM dissolution rate and BS concentration at a constant L concentration, good curve-fittings were obtained when the BS monomer concentration was set to equal the critical micellar concentration (CMC). For taurochenodeoxycholate (TCDC), a dihydroxy BS, the resulting values of parameters show that the simple TCDC micelle rate constant (ks) increases, but the mixed TCDC-L micelle rate constant (ku) decreases with increasing L concentrations. As for taurocholate (TC), a trihydroxy BS, a ChM dissolution study was conducted over the initial 2 hour period in different TC-L solutions. A similar curve-fitting analysis revealed that the simple TC micelle ks is independent ofL concentration and is much higher than the kM of mixed TC-L micelles. Moreover, the outcome of the analysis supports previously reported equilibrium dialysis study results concerning the BS to L ratio of mixed BS-L micelles. According to the collision theory, the resulting ks and kM values are interpreted.