Phenols are an important group of natural products with antioxidant and other bio­logical activities. These compounds play an important role in algal cell defense against abiotic and biotic stress. Several authors have recently published results regarding the total phenol content and antioxidant activity of algae [40] . Cinnamic acid esters (n-butyl 3,5-dimethoxy-4-hydroxycinnamate and isopropyl 3,5-dimethoxy-

4- hydroxycinnamate) and methyl 3,4,5-trihydroxybenzoate were studied using 1H and 13C NMR in brown algae Spatoglossum variabile [46]. Some of the first polyphenols found in algae (Fucus and Ascophyllum spp.) were phlorotannins. They are formed from the oligomeric structures of phloroglucinol (1,3,5-trihydroxyben — zene) [137]. Also, some flavanone glycosides have been found even in fresh water algae [86] .

The main bioactivity associated to phenolic compounds is antioxidant activity, which is also the main bioactivity of algal and microalgal phenolics [89]. Duan et al. [28] have demonstrated that antioxidant potency of crude extract from red algae (Polysiphoma urceoiata) correlated well with the total phenolic content. Strong cor­relation also existed between the polyphenol content and DPPH radical scavenging activity of a seaweed (H. fusiformis) extract [177], Using electron spin resonance spectrometry and comet assay, Heo et al. [51] found that phenolic content in sea­weeds could raise up to 1,352 mg/g on dry weight basis. The content and profile of phenolic substances in marine algae vary with the species. In marine brown algae, a group of polymers called phlorotannins comprises the major phenolic compounds [20], such as fucols, phlorethols, fucophlorethols, fuhalols, and halogenated and sulfited phlorotannins. Takamatsu et al. [186] showed that bromophenols isolated from several red marine algae exhibited antioxidant activities. These findings sug­gest that phlorotannins, the natural antioxidant compounds found in edible brown algae, can protect food products against oxidative degradation as well as prevent and/or treat free radical-related diseases [89] .

Some algal phenolic compounds have been associated with anti-inflammatory activity, such as rutin, hesperidin, morin, caffeic acid, catechol, catechin, and epi — gallocatechin gallate, whose have been identified in Porphyra genus. Kazlowska et al. [79] have studied recently the phenolic compounds in Porphyra dentata, they identified catechol, rutin, and hesperidin in crude extract using HPLC-DAD. They demonstrated that the crude extract and the phenolic compounds inhibited the production of nitric oxide in LPS-stimulated RAW 264.7 cells. Their results indicate that catechol and rutin, but not hesperidin, are primary bioactive phenolic compounds in the crude extract to suppress NO production in LPS-stimulated macrophages via NF-kB-dependent iNOS gene transcription. Data also explained the anti-inflammatory use and possible mechanism of P. dentata in iNOS — implicated diseases.