ABSTRACT
AIM To investigate the equilibrium solubilities,oil-water partition coefficients and in vitro skin permeation features of brucine and strychnine in total alkaloids from Strychni Semen.METHODS Saturated dissolution method was applied to determining the equilibrium solubilities of two constituents in ethanol (10％,20％,30％,60％,90％,anhydrous ethanol),trichloromethane,n-octanol and surfactants (0.5％ tween,0.5％ sodium deoxycholate,0.5％ oleic acid).Shake-flask method was adopted in detecting their oil-water partition coefficients in PBS (pH 2.5,4.0,5.0,5.8,6.8,7.0,7.4,9.0).Modified Franz diffusion cell method was used for evaluating their in vitro skin permeation features in PBS,20％ ethanol and anhydrous ethanol.RESULTS Both brucine and strychnine showed the highest equilibrium solubilities in trichloromethane and the lowest equilibrium solubilities in surfactants.The equilibrium solubility of strychnine was higher than that of brucine in ethanol (＞ 20％) or PBS (pH ＜ 8.0),which reached the highest in 60％ ethanol and pH 2.5 PBS,respectively.The similar oil-water partition coefficients of two constituents,proportional to pH value,reached the highest at pH9.0.And they exhibited the highest accumulated transdermal absorptivities in anhydrous ethanol and pH 9.0 PBS,respectively.CONCLUSION Solvent type has obvious effects on the equilibrium solubilities,oil-water partition coefficients and in vitro skin permeation features of both brucine and strychnine.This study can provide a reference for the bioavailability improvement of transdermal drug delivery and development of related preparations.
ABSTRACT
AIM To investigate the equilibrium solubilities,oil-water partition coefficients and in vitro skin permeation features of brucine and strychnine in total alkaloids from Strychni Semen.METHODS Saturated dissolution method was applied to determining the equilibrium solubilities of two constituents in ethanol (10％,20％,30％,60％,90％,anhydrous ethanol),trichloromethane,n-octanol and surfactants (0.5％ tween,0.5％ sodium deoxycholate,0.5％ oleic acid).Shake-flask method was adopted in detecting their oil-water partition coefficients in PBS (pH 2.5,4.0,5.0,5.8,6.8,7.0,7.4,9.0).Modified Franz diffusion cell method was used for evaluating their in vitro skin permeation features in PBS,20％ ethanol and anhydrous ethanol.RESULTS Both brucine and strychnine showed the highest equilibrium solubilities in trichloromethane and the lowest equilibrium solubilities in surfactants.The equilibrium solubility of strychnine was higher than that of brucine in ethanol (＞ 20％) or PBS (pH ＜ 8.0),which reached the highest in 60％ ethanol and pH 2.5 PBS,respectively.The similar oil-water partition coefficients of two constituents,proportional to pH value,reached the highest at pH9.0.And they exhibited the highest accumulated transdermal absorptivities in anhydrous ethanol and pH 9.0 PBS,respectively.CONCLUSION Solvent type has obvious effects on the equilibrium solubilities,oil-water partition coefficients and in vitro skin permeation features of both brucine and strychnine.This study can provide a reference for the bioavailability improvement of transdermal drug delivery and development of related preparations.
ABSTRACT
Metastable and equilibrium phase diagrams for unconjugated bilirubin IXα (UCB) in bile are yet to be determined for understanding the physical chemistry of pigment gallstone formation. Also, UCB is a molecule of considerable biomedical importance because it is a potent antioxidant and an inhibitor of atherogenesis. We employed principally a titrimetric approach to obtain metastable and equilibrium UCB solubilities in model bile systems composed of taurine-conjugated bile salts, egg yolk lecithin (mixed long-chain phosphatidylcholines), and cholesterol as functions of total lipid concentration, biliary pH values, and CaCl2 plus NaCl concentrations. Metastable and equilibrium precipitation pH values were obtained, and average pKa values of the two carboxyl groups of UCB were calculated. Added lecithin and increased temperature decreased UCB solubility markedly, whereas increases in bile salt concentrations and molar levels of urea augmented solubility. A wide range of NaCl and cholesterol concentrations resulted in no specific effects, whereas added CaCl2 produced large decreases in UCB solubilities at alkaline pH values only. UV-visible absorption spectra were consistent with both hydrophobic and hydrophilic interactions between UCB and bile salts that were strongly influenced by pH. Reliable literature values for UCB compositions of native gallbladder biles revealed that biles from hemolytic mice and humans with black pigment gallstones are markedly supersaturated with UCB and exhibit more acidic pH values, whereas biles from nonstone control animals and patients with cholesterol gallstone are unsaturated with UCB.
