Abstract

Background: Cyanobacteria are the predominant atmospheric nitrogen fixers of the aquatic as well as terrestrial ecosystems. Harvesting of solar energy for photosynthesis exposes cyanobacteria simultaneously to lethal doses of ultraviolet radiation (UVR) in their natural brightly light habitats. To counteract the damaging effect of UVR, cyanobacteria synthesize novel secondary metabolites such as mycosporine-like amino acids (MAAs) and scytonemin. By the application of the “omics” techniques cyanobacterial molecular biology is benefitted tremendously. Traditionally, only small sets of metabolites are quantified in targeted metabolome approaches. The development of separation technologies coupled with mass-spectroscopy and nuclear-magneticresonance based identification of low molecular mass molecules allows the profiling of several metabolites of different chemical nature.

Objective: MAAs and scytonemin are highly photostable and act as potent photoprotectant and antioxidant hence can be biotechnologically exploited by the cosmetic industry. Till date, 23 MAAs such as shinorine, mycosporine glycine, palythine, palythinol, asterina-330 and porphyra-334, and 7 different forms of scytonemin such as oxidized and reduced scytonemin, scytonemin-3a-imine and scytonemin A have been reported in various cyanobacteria. Metabolome analysis could be applied to characterize changes in the cyanobacterial primary and secondary metabolites such as MAAs and scytonemin under diverse environmental conditions. Untargeted metabolite profiling has the potential to identify numerous novel metabolites; however, de novo identification of metabolites from spectral features remains a challenge.

Conclusion: This review deals with the structure, biosynthesis and various techniques involved in the metabolomic profiling of cyanobacterial UV protective compounds scytonemin and MAAs.

Keywords: Cyanobacteria, ultraviolet radiation, mycosporine-like amino acids, scytonemin, spectroscopy, metabolomics; high performance liquid chromatography

Graphical Abstract