Quantitative determination of major phlorotannins in Ecklonia stolonifera
Ecklonia stolonifera is a rich source of phlorotannins, which are responsible for the potent pharmacological effects associated with this seaweed. The purpose of this study was to develop a reversed-phase high-performance liquid chromatography method for the simultaneous determination of three major phlorotannins, eckol, dieckol, and phlorofucofuroeckol-A, in the extracts of Ecklonia stolonifera. The optimal chromatographic conditions were achieved on a Thermo Hypersil Gold C-18 column (250 × 4.6 mm i.d., 5 μm) using linear gradient elution of acetonitrile and water containing 0.1% formic acid at UV 254 nm. The separated phlorotannins were identified by liquid chromatography-mass spectrometry. The high-performance liquid chromatography method showed good linearity (r2 > 0.998), precision (1.4–9.5%), and accuracy (93.9–108.7%). The limits of detection ranged from 0.06 to 0.30 μg/mL and the lower limits of quantitation ranged from 0.2 to 1.0 μg/mL. Among phlorotannins, dieckol was the most abundant in both ethanol and ethyl acetate extracts of Ecklonia stolonifera.