Objective:To study on transdermal diffusion behavior of active ingredients from compound Nanxing Zhitong plaster in different media. Method:The improved Franz diffusing cell was adopted with skin of nude mice in vitro as transdermal barrier.The transdermal diffusion behavior of active ingredients in compound Nanxing Zhitong plaster was carried with physiological saline

pH 7.4 phosphate buffer solution or 30% polyethylene glycol(PEG)400 normal saline as the receiving medium.The chromatographic condition was established to determine the contents of cinnamic acid

paeonol

eugenol

cinnamic aldehyde and methyl salicylate in the sample.HPLC separation was performed on detection wavelengths of 276 nm and 320 nm by using acetonitrile-0.1% acetic acid aqueous solution as the mobile phase for gradient elution. Result:With physiological saline and pH 7.4 phosphate buffer solution as the receiving media

the diffusion regulation of paeonol and eugenol accorded with zero order kinetics and the first-order kinetics equation

while the diffusion action of methyl salicylate accorded with Ritger-Peppas equation.Cinnamic acid and cinnamic aldehyde had reciprocal transformation in the physiological saline.After diffusion of 10 h

the release amount of cinnamic acid increased significantly

while cinnamic aldehyde had a big drop.Cinnamic acid and cinnamic aldehyde were no longer increased after 10 h with the saturation condition in pH 7.4 phosphate buffer solution.With 30% PEG400 normal saline as the receiving medium

the diffusion regulation of paeonol and eugenol also accorded with zero order kinetics and the first-order kinetics equation

while the diffusion action of methyl salicylate was closer to the Higuchi equation.The transformation of cinnamic acid and cinnamic aldehyde was not obvious in 30% PEG400 normal saline

after diffusion of 12 h

the release amount of cinnamic acid released continuously

while cinnamic aldehyde was no longer released after the release finished. Conclusion:When 30% PEG400 normal saline as receiving medium

transdermal diffusion rates of active ingredients in compound Nanxing Zhitong plaster are significantly better than the other two receiving media

and it can inhibit the conversion of cinnamic aldehyde to cinnamic acid.