Objective: To prepare delivery system of ursolic acid self-microemulsion

and establish bioavailability and pharmacokinetics of ursolic acid self-microemulsion by HPLC-MS. Method: Ursolic acid self-microemulsion delivery system was prepared with OP emulsifier

Tween-20

isopropyl alcohol and oleic acid

and investigated its stability

particle size and Zeta potential.In vivo bioavailability and pharmacokinetics in rats were evaluated by oral administration. Result: Ursolic acid self-microemulsion was stable within a month

average particle size and Zeta potential were 32.74 nm and 4.21 mV

respectively.Relative bioavailability of ursolic acid self-microemulsion and sustained-release tablets were 326.5% and 256.6%

respectively; and then relative bioavailability of microemulsion delivery system was 127.2% to sustained-release tablets. Conclusion: This prepared self-microemulsion delivery system could enhance bioavailability of ursolic acid.