Pharmacokinetics and tissue distribution of emodin loaded nanoemulsion in rats

Emodin, a natural product originated from radix et rhizoma Rhei, is a potential agent for anti-constipation, anti-inflammation, anti-cancer and so on. In this paper, a simple, economic and sensitive HPLC-FD method was developed and validated for the determination of emodin in rat plasma and tissue homogenates after oral administration of emodin loaded nanoemulsion (EMO-NE). Simultaneously, the pharmacokinetics of EMO-NE and emodin suspension were investigated so as to embody advantages of EMO-NE. AUC0−∞, Cmax, t1/2 and MRT0−∞ of emodin-loaded nanoemulsion were respectively 2.37, 1.62, 3.99 and 2.39-fold higher than those of emodin suspension. Meanwhile, EMO-NE decreased the clearance rate of emodin more than double that of emodin suspension. Thus, it can be assumed that EMO-NE can effectively improve the bioavailability of emodin and prolong in vivo mean residence time via oral administration. All tested tissues of rats were found to retain parent drug for 48 h following a single oral dose of EMO-NE. The amount of emodin was the highest in the liver, and then lung, kidney, heart or spleen, and lowest in the brain. However, the mean residence time of emodin in the brain was the longest, almost two-fold longer than that in the other tissues.

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