Phenols (sometimes called phenolics) are a class of chemical compound consisting of a hy­droxyl group (-OH) directly bound to an aromatic hydrocarbon group. The simplest of this class is phenol, the parent compound used as disinfectant and for chemical synthesis. Phlorotannins are an extremely heterogeneous group of phenolic compounds in terms of structure and degree of polymerization; accordingly, they provide a wide range of biological activities (Holdt and Kraan, 2011). Green and red macroalgae possess low concentrations of phenols (Mabeau and Fleurence, 1993) compared to brown macroalgae that are particularly rich in phlorotannin. Typical phenolic contents vary from 1-14% of dry macroalga biomass. Such polyphenols as fucol, fucophlorethol, fucodiphloroethol G, and ergosterol as well as phlorotannin are abundant in brown macroalgae and possess strong antioxidant effects. The concentration of polyphenols exhibits seasonal variations and shows a significant time correlation with the algal reproductive state, besides being affected by a number of other parameters such as location and salinity (Holdt and Kraan, 2011).

Polyphenols entail a cosmetic and pharmacological value owing to their antioxidative activity; they also have shown other favorable effects, e. g., protection from radiation as well as antibiotic and antidiabetic qualities. Several of these effects were tested in bacteria, cell cultures, rodents, and even humans, namely with regard to sexual performance and desire. Certain polyphenols may work as preventative medicines due their several bioactivities (see Table 10.6); in particular, phlorotannins are candidates for development of unique natural antioxidants for further industrial applications in functional food, cosmetic, and pharmaceu­tical formulations (Li, Qian et al., 2009).

For their extraction, several methods can be applied using Soxhlet-based solvent extraction or ultrasonic extraction, as discussed elsewhere (Mahugo Santana, Sosa Ferrera et al., 2009).