A Pharmacokinetic and Bioavailability Study of Ecklonia cava Phlorotannins Following Intravenous and Oral Administration in Sprague–Dawley Rats

This study examines the pharmacokinetics and bioavailability of phlorotannins from <i>Ecklonia cava</i> in rats following intravenous and oral administration. Known for their potent antioxidant, anti-inflammatory and many other bioactivities, these phlorotannins, particularly dieckol, 8,8'-bieckol, and phlorofucofuroeckol-A (PFF-A), were analyzed using high-performance liquid chromatography coupled with tandem mass spectrometry. Intravenous administration at 10 mg/kg allowed detectability in plasma for up to 36 h for dieckol and 8,8'-bieckol, but only 2 h for PFF-A. Oral administration at doses of 100 mg/kg and 1000 mg/kg showed limited detectability, indicating low bioavailability and rapid clearance, particularly for PFF-A. The pharmacokinetic data suggest non-linear increases in the maximum plasma concentration (C_max) and area under the curve (AUC) with increasing doses, pointing to significant challenges in achieving systemic availability of these eckols through oral administration. This study underscores the necessity for advanced formulation strategies and alternative routes of administration to enhance systemic bioavailability. At the same time, this result also suggests their effects may be through non-systemic pathways such as gut microbiome modulation or lipid-rich tissue targeting. The findings lay a crucial foundation for the further development of <i>Ecklonia cava</i> phlorotannins as therapeutic agents, offering insights into their pharmacokinetic behavior and informing enhancements in future clinical utility.