Bioaccessibility and Bioavailability of Phenolic Compounds in Seaweed

Seaweeds are rich in phenolic compounds such as phlorotannins and have antioxidant, antibacterial, and anti-inflammatory activities. As exogenous bioactive compounds, seaweed polyphenols exist in the form of aglycone, esters, glycosides, and polymers. Most of them are not directly absorbed in the human digestive tract but undergo extensive modifications by digestive enzymes or bacteria before absorption or excretion. Up-to-date in vitro and in vivo seaweed polyphenol bioaccessibility studies have been reviewed, outlining seaweed polyphenols, especially phlorotannins, have low oral bioaccessibility, bioavailability, and high bioactivity paradox. Moreover, special attention is also given to other factors such as food matrix, food processing methods, and host factors on the absorption of seaweed polyphenols. In digestion tract, proteins can form both covalent and non-covalent bonds with polyphenols and thus hinder the absorption of polyphenols. However, lipids and polysaccharides in food can enhance the bioaccessibility of polyphenols to some extent. It is worth noticing that food processing technologies and host gut flora composition can also alter the absorption and bioactivity of specific seaweed phenolics.