Water anti-algae

Tannins are naturally occurring water-soluble polyphenolic compoimds, and it has been reported that they show their anti-HIV activity by inhibiting polymerase and ribonuclease activities of HIV-1 RT. Phlorotannins are tannin derivatives which contain several phloroglucinol imits linked to each other in different ways and formed by the polymerization of phloroglucinol (1,3,5-trihydroxybenzene) monomer units and biosynthesis through the acetate-malonate pathway. So far, phlorotannins mostly have been isolated from red and brown alga. Numerous bioactivities of phlorotannins have been reported up to date such as antioxidant, antiinflammatory, antibacterial, and anti-MMP activities (Kim et al., 2006 Nagayama et al., 2002). 

Many cyanobacteria live in tropical zones in the vicinity of the water surface and are thus subjected to solar radiation, in particular the ultraviolet B (UV B) wavelength (280-320 nm). Certain species thus developed antiradical systems to protect themselves from this radiation. One of these substances is scytonemin, a brown-yellow dimeric pigment of heteroaromatic nature, of which the first observation was made by Nageli in 1849, who obtained it from a species of the genus Scytonema. This compormd, the structure of which was established in 1993, stiU seems to be specific to cyanobacteria, and in a more general way to prokaryotes, although it is present in very many species (Proteau et al, 1993). For an overview on the anti-UV substances of cyanobacteria, of phytoplankton and macro-algae, see Sinha et ol. (1998). Scytonemin absorbs in the three fields of the ultraviolet rays UV-A (325—425 nm) UV-B (280-320 nm) and UV-C (250 nm). 

---