Apolipoproteins A-1 and A-2 were purified from human plasma. At concentrations present in human bile these proteins prolonged the nucleation time of cholesterol monohydrate crystals when added to model systems of supersaturated bile. In contrast, apolipoprotein C-3 and other serum proteins did not have this effect. Also, when human gallbladder bile was fractionated by gel filtration chromatography, apolipoproteins A-1 and A-2 were among the proteins present in a fraction of bile enriched in potent inhibitors of cholesterol crystal nucleation. These findings suggest that apolipoproteins A-1 and A-2 in supersaturated human gallbladder bile could inhibit the rate of formation of solid cholesterol crystals and thus help to prevent spontaneous cholesterol gallstone formation in humans.

Resolution of mandelic acid (MA), a racemic compound, is presented in this article using direct crystallization from enantiomeric enriched water solutions. Final crystals with enantiomeric excess (ee) of (R)-MA higher than 96.4% were obtained. Because of the presence of the opposite enantiomer ((S)-MA), it was reported that nucleation and growth of (R)-MA was inhibited at the initial stage of the experiment (Perlberg, et al. Ind. Eng. Chem. Res. 2005, 44, 1012-1020. In order to understand the nucleation and growth kinetics of (R)-MA in the presence of (S)-MA, batch crystallization experiments were performed for controlled linear cooling mode with various operating conditions. Nucleation and growth parameters were then estimated by nonlinear fitting the measured liquid concentrations obtained from the signals of in situ attenuated total reflectance infrared (ATR-IR) spectroscopy and online polarimetry with model predictions. The effects of supersaturation, seed amount, cooling rate, and the presence of opposite enantiomer on the growth and nucleation rate of (R)-MA were discussed.

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In this work the solubility of two polymorphic forms A and B of erlotinib hydrochloride in isopropanol (IPA) and acetone were determined by means of high-performance liquid chromatography (HPLC) in the temperature range from (273.15 to 303.15) K. The experimental data were correlated with the modified Apelblat equation. In particular, the effect of the surfactant Tween 80 on the solubility of both polymorphs was studied as well. The results show that the solubility of both polymorphs generally increases with the temperature, and polymorph A has a higher solubility than polymorph B which indicates that polymorph A is the metastable form. The modified Apelblat equation shows a good agreement with the experimental data with a percent error less than 3 %. Furthermore, the solubility of both polymorphs increases in a linear fashion with increasing the content of Tween 80 in organic solvents, wherein Tween 80 presents a same solubilization capacity to both polymorphs and a higher solubilization capacity in acetone than in IPA.

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Resolution of racemic mandelic acid ((R,S)-MA) and numerical determination of binary competitive isotherm of (R,S)-MA on Chiralcel-OD column have been investigated in this study. The effects of the alcohol modifier and acidic additive in the mobile phase on the retention and enantioseparation of (R,S)-MA were studied at first. The inverse method was then used to determine the competitive isotherm parameters of (R,S)-MA by minimizing the sum of square deviations of the model predictions from the measured elution profiles. The results indicate that the mobile phase with 85% hexane/15% isopropanol/0.3% trifluoroacetic acid mixture gives the best resolution of (R,S)-MA and competitive-modified Langmuir isotherm provides the more accurate sorption mechanism of (R,S)-MA on the cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase.