High Quality Content by WIKIPEDIA articles! Phlorotannins are a type of tannins found in brown algae such as kelps and rockweeds or sargassacean species. Contrary to hydrolysable or condensed tannins, these compounds are oligomers of phloroglucinol (polyphloroglucinols). As they are called tannnins, they have the aility to precipitate proteins. It has been noticed that some phlorotannins have the ability to oxidize and form covalent bonds with some proteins. In contrast, under similar experimental conditions three types of terrestrial tannins (procyanidins, profisetinidins, and gallotannins) apparently did not form covalent complexes with proteins.