ABSTRACT
Objective To determine equilibrium solubility and apparent oil/water partition coefficient of ephedra alkaloid in the compatibility Ephedrae Herba-Aconiti Lateralis Radix Praeparata; To provide a basis for transdermal delivery.Methods The extract was prepared by 70% ethyl alcohol and D101 macroporous absorbent resins. Dissolvability of its main effective components (ephedrine and pseudoephedrine) in the compatibility Ephedrae Herba-Aconiti Lateralis Radix Praeparata was determined by precipitation method and HPLC method; the oil/water partition coefficient of ephedrine and pseudoephedrine in n-octanol-water buffer solution system were determined by shaking flask method.Results The extract had optimum solubility in methyl alcohol and acetonitrile, and ephedrine and pseudoephedrine had optimum solubility in buffered solution of pH 7.4. Oil/water partition coefficient of ephedrine and pseudoephedrine in n-octanol-water system was 0.101 with lgP=-0.99 and 0.076 with lgP=-1.12. Oil-water partition coefficients of ephedrine and pseudoephedrine in the extract were affected by pH.Conclusion The extract has optimum solubility in high polar solvents. Ephedrine and pseudoephedrine have certain fatsoluble and water-soluble in suitable pH, which was beneficial for transdermal absorption.