The exact whole biosynthetic pathway for a Sea polyphenol is unknown.

However, in the early biosynthetic steps of its monomer, phloroglucionol, two molecules of acetyl co-enzyme A are converted into malonyl co-enzyme A through the addition of carbon dioxide. This changes the acetyl methyl group into a highly reactive methylene and so assists the process of polymerization to occur without the need for a high investment of energy. During further synthesis steps, the carbon dioxide, which was added as an activator, is lost.

The result of polymerization is a polyketide chain consisting of an acid moiety, and the co-enzyme is lost. The polyketide chain is transformed by intermolecular ring closure and elimination of water to produce hexacyclic ring systems .

Triketide, the cyclization product, is not stable and thus undergoes transformation (tautomerisation) into the thermodynamically more stable aromatic form, phloroglucinol, consisting of three phenolic hydroxyl groups (Waterman PG and Mole S. 1994. Analysis of phenolic plant metabolites. Blackwell Scientific Publications: Oxford, Great Britain.

Further elements of the biosynthetic pathway are unknown.