Microwave-Assisted Extraction of Phlorotannins from Fucus vesiculosus

Microwave-assisted extraction (MAE) was carried out to maximize the extraction of phlorotannins from Fucus vesiculosus using a hydroethanolic mixture as a solvent, as an alternative to the conventional method with a hydroacetonic mixture. Optimal MAE conditions were set as ethanol concentration of 57% (v/v), temperature of 75 degrees C, and time of 5 min, which allowed a similar recovery of phlorotannins from the macroalgae compared to the conventional extraction. While the phlorotannins richness of the conventional extract was slightly superior to that of MAE (11.1 +/- 1.3 vs. 9.8 +/- 1.8 mg PGE/g DWextract), both extracts presented identical phlorotannins constituents, which included, among others, tetrafucol, pentafucol, hexafucol, and heptafucol structures. In addition, MAE showed a moderate capacity to scavenge ABTS(center dot+) (IC50 of 96.0 +/- 3.4 mu g/mL) and to inhibit the activity of xanthine oxidase (IC50 of 23.1 +/- 3.4 mu g/mL) and a superior ability to control the activity of the key metabolic enzyme alpha-glucosidase compared to the pharmaceutical drug acarbose.