The effect of stealth liposomes on pharmacokinetics, tissue distribution and anti-tumor activity of oridonin.

High-purity oridonin was isolated and identified from Rabdosia rubescens hemsl by preparative high-performance liquid chromatography (HPLC). Stealth liposomes of oridonin were prepared by thin-film ultrasonic dispersion using polyethylene glycol-distearoylphosphatidyleth-anolamine(PEG2000-DSPE) as the surface-coating material. A reversed-phase HPLC method was developed and validated to determine the concentrations of oridonin in the serum and tissues of mice. The tissue distribution and pharmacokinetics of oridonin stealth liposomes and oridonin solution in mice were investigated. The results showed that the distribution and pharmacokinetics of oridonin stealth liposomes in mice were changed as compared to the distribution and pharmacokinetics of oridonin solution. The levels of stealth liposomal oridonin in the heart tissues were reduced, while the levels of stealth liposomal oridonin in the blood were increased. The stealth liposomes were very effective at inhibiting the rate of solid tumor growth. The PEG2000-DSPE of liposomes prolonged the circulation time of oridonin in mouse blood, reduced accumulation in the reticuloendothelial system and increased the anti-tumor activity of oridonin.