Comparative Study on the Transdermal Penetration Enhancement Effect of Essential Oils of Interior-Warming Drugs Based on Electrical Resistance of Skin

OBJECTIVE To evaluate and establish a method for rapid comparison of transdermal penetration enhancement effect of essential oils （EOs） from Chinese materia medica (CMM). METHODS  The active components （ferulic acid，albiflorin，paeoniflorin，tetrahydrocolumbamine，tetrahydropalmatine） in Xiangfu Siwu Decotion （XFSWD）were used as model drugs for transdermal permeation study. The oil/water partition coefficient values of the above active components were measured. Six EOs of interior-warming drugs were used as penetration enhancer （PE）. The Franz diffusion cell method was applied to investigate the effects of EOs on transdermal permeation of active components in XFSWD. The impact of EOs on skin integrity was evaluated by electrical resistance （ER） of the skin. Finally，the correlation between the results of skin resistance dynamics and in vitro transdermal permeation experiment was assessed. RESULTS The oil-water partition coefficients of ferulic acid，albiflorin，paeoniflorin，tetrahydrocolumbamine，tetrahydropalmatine were measured to be -0.93，-0.59，-0.38，1.97， 2.15. Six EOs of interior-warming drugs as PE could significantly enhance the permeation of active components in XFSWD，especially the polar components. The EOs with hot nature possess better penetration ability than that of warm nature. Besides，there was a good correlation between the results of skin resistance dynamics and in vitro transdermal permeation experiments for above drugs with different polarity(r=0.748 1-0.812 9). CONCLUSION The penetration enhancing effect of EOs of interior-warming drugs are affected by drug four nature property characteristics of CMM.The ER method can effectively identify the penetration enhancing effect of EOs.