Analysis of the pharmacokinetics and metabolism of aloe-emodin following intravenous and oral administrations in rats.

Aloe-emodin, a natural polyphenolic anthraquinone, has shown various beneficial bioactivities in vitro. The aim of this study was to investigate the pharmacokinetics and metabolism of aloe-emodin. Aloe-emodin was intravenously and orally administered to rats. The concentrations of aloe-emodin and rhein, a metabolite of aloe-emodin, were determined by HPLC method prior to and after hydrolysis with β-glucuronidase and sulfatase/β-glucuronidase. The results showed that the systemic exposures of aloe-emodin and its metabolites were ranked as aloe-emodin glucuronides (G) > rhein sulfates (S) > aloe-emodin > rhein and rhein G when aloe-emodin was given intravenously. In contrast, when aloe-emodin was administered orally, the parent form of aloe-emodin was not absorbed per se, and the systemic exposures of its metabolites were ranked as aloe-emodin G > rhein G > rhein. In conclusion, the metabolites of aloe-emodin are more important than the parent form for the bioactivities in vivo.