BIOPROSPECTION OF UV-SCREENING COMPOUNDS FROM LICHENS INHABITING THE INDIAN STATE OF SIKKIM

Abstract

Lichens show mutualistic relationship between algae/cyanobacteria and fungi and are found in diverse environmental conditions ranging from sea levels to high alpine elevations. They can tolerate and survive in harsh environmental conditions such as habitats having low temperature, desiccation, high temperature and ultraviolet radiation (UVR). Lichens have developed several photoprotective mechanisms such as light scattering, radiation screening, activation of antioxidants and macromolecules, thermal dissipation, membrane repair and synthesis of UV protective compounds such as despides, diphenyl ether, xanthones, anthraquinones, mycosporines, mycosporine-like amino acids (MAAs) and scytonemin to cope up with damaging UVR. MAAs are water-soluble molecules that absorb short wavelength solar UVR and disperse the energy as heat. Scytonemin is a small hydrophobic alkaloid pigment present in the extracellular sheath of several cyanobacteria as a protective mechanism against UVR. In the present study, bioprospection of lichen was done for screening of UV-absorbing compounds MAAs and scytonemin from different regions of Sikkim, India. Tentative identification and partial purification of these compounds was done with the help of high-performance liquid chromatography. Scytonemin showed absorption maxima at 252, 278, 385 nm and peaks at 347 and 410 nm showed the presence of scytonemin-3a-imine and gloeocapsin respectively. MAAs showed absorption maxima at 325.1 and 308 nm corresponding to mycosporine-NMA:Ser and mycosporine-taurine respectively. Scytonemin and MAAs display multiple roles, functioning as a potent UV-sunscreen and antioxidant molecules, and can be exploited in cosmetic and other industries for the development of novel drugs and pharmaceuticals, hence their bioprospection from different sources becomes crucial