Determination of major phlorotannins in Eisenia bicyclis using hydrophilic interaction chromatography: Seasonal variation and extraction characteristics

In this study, a hydrophilic interaction chromatography (HILIC) condition was developed for the simultaneous determination of five major phlorotannins from an extract of Eisenia bicyclis (Kjellman) Setchell with good linearity (r² > 0.999). Based on this method, the seasonal variations and extraction characteristics, in terms of total extraction yield and the content of the phlorotannins, were investigated under various extraction conditions. In results, the yields and phlorotannins were increased two-to-four times in summer (June–October) and then, were decreased to normal levels in winter (November–March). In the extraction of E. bicyclis, ethanol percentage in water, extraction time and washing time significantly affected the yield of the extract and the phlorotannins, whereas the temperature and the sample/solvent ratio impacted the extraction to a lesser degree. These results will be useful information in the application of this macroalga in the commercial areas related to nutraceuticals, pharmaceuticals, and cosmeceuticals.