Objective: The aim of this study was to develop a novel W/O microemulsion for a natural
extract of Wen-Luo-Tong (WLT) containing mainly icariin, hydroxysafflor yellow A (HSYA) and gallic
acid to be applied to skin as a potential treatment for peripheral neuropathy.
Methods: The oil phase was selected on the basis of affinity with the surfactant and co-surfactant.
Pseudo-ternary diagrams were constructed to optimize microemulsions and finally stability studies were
performed on the selected formulations. Droplet sizes were analyzed by using a zetasizer and were
found to be within the desired range. Selected microemulsions with acceptable viscosities, containing
5%, 8% and 10% of water extract solution, were used for in vitro skin penetration studies using Franz
diffusion cells and excised rat skin. New LC-MS/MS and UPLC-Q-TOF/MS methods were employed
for quantitative and qualitative analysis.
Results: The optimized formulation (ME-4) consisting of 10% (w/w) water extract solution, 60% isopropyl
myristate, 30%(w/w) Smix: Propylene glycol (5:2) significantly increased the cumulative permeated
amounts of HSYA, icariin and gallic acid compared with the water extract solution controls.
Conclusion: This novel formulation also increased the number of components penetrating rat skin. Ten
components were detected in the Franz cell receptor solution using a UPLC-Q-TOF/MS system after the
application of formulation ME-4 for 24h on the skin in vitro. However, only one component was detected
after applying the control. Therefore, the microemulsion ME-4 was selected for future in vivo