Eckstolonol is a

phlorotannin Phlorotannins are a type of tannins found in brown algae such as kelps and rockweeds or sargassacean species, and in a lower amount also in some red algae. Contrary to hydrolysable or condensed tannins, these compounds are oligomers of phloro ...

found in the edible brown algae

arame , sea oak is a species of kelp, of the brown algae, best known for its use in Japanese cuisine. Description ''Eisenia bicyclis'' is indigenous to temperate Pacific Ocean waters centered near Japan, although it is deliberately cultured elsewh ...

(''Eisenia bicyclis'') and turuarame (''Ecklonia stolonifera'').

References

Phlorotannins {{aromatic-stub