**4.3 Phenolic and polyphenols compounds**

The secondary metabolites are polyphenols. They are a collection of chemical substances found in aquatic macrophytes and terrestrial plants. Phenolic compounds are present in edible plants, and their structure contains benzene [71]. Plants frequently contain phenolic chemicals. Polyphenols contain tannins, phenolic acids, flavonoids, tocopherols, and lignin.


**Table 3.** *Algal metabolites.*
