Aquatic Microalgae As Potential Sources Of Uv-Screening Compounds

Microalgae are a polyphyletic and biochemically diverse assemblage of chlorophyll a-containing microorganisms capable of oxygenic photosynthesis that are predominantly found in aquatic environments with observed high levels of ultraviolet (UV) radiation. Certain microalgae produce organic metabolites, such as sporopollenin, scytonemin and mycosporine-like amino acids, to protect themselves from UV radiation while allowing visible radiation involved in photosynthesis to pass through. Sporopollenin, an acetolysis-resistant inert biopolymer usually observed in plant pollens and spores, was detected in the cell wall of some UV-tolerant chlorophytes. Scytonemin, a yellow-brown lipid-soluble dimeric pigment, was found in the extracellular polysaccharide sheath of some cyanobacteria. Mycosporinelike amino acids, which belong to a family of water-soluble compounds, were reported in several free-living cyanobacteria, chlorophytes, haptophytes, diatoms, and dinoflagellates, as well as in several marine invertebrate-microalgal symbiotic associations. Their capacity to intercept UV radiation and dissipate its energy as heat without the formation of radical intermediates makes these microalgal compounds potential sources of protection from UV and photo-oxidative stress.