ORIGINAL PAPER Screening of antioxidant potential of Arctic lichens Shiv M. Singh • Purnima Singh • Rasik Ravindra Received: 25 November 2010 / Revised: 17 February 2011 / Accepted: 18 February 2011 / Published online: 13 May 2011 Ó Springer-Verlag 2011 Abstract Antioxidants are compounds that scavenge the free radicals produced in living organisms. The antioxidant potential of eight Arctic lichen species was evaluated in vitro using free radical scavenging activity (FRS), inhibi- tion of lipid peroxidation (ILP), and Trolox equivalent antioxidant capacity assay (TEAC). FRS activities of lichen species in various organic solvents such as metha- nol, ethanol, acetone, and dimethyl sulphoxide (DMSO) were in the range 9.6–51.77%, while ILP activities in these solvents ranged from 32.5 to 82.43%. Pseudophebe pu- bescens showed the highest ILP (82.43%) and FRS (51.77%) activities as compared to other lichen species and the standard antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The TEAC value was also found to be higher in all species compared to the standard water soluble vitamin E analog Trolox (3.9 mM). The order of antioxidative activities in lichen species was Pseudophebe pubescens [ Cladonia amaurocraea [ Cla- donia mediterranea [ Physcia caesia [ Flavocetraria nivalis [ Cetraria fastigata [ Xanthoria elegans [ Umbilicaria hyperborea. This is the first report of the measurement of antioxidant potential in Arctic lichens. Keywords Bioprospecting  Lichen  Extreme environment  Ny-A ˚ lesund  Svalbard Introduction The Arctic flora is inhabited by lower plant groups such as lichens, mosses, liverworts, and algae with relatively few vascular plants (Matveyeva and Chernov 2000). About 3% of the global flora occurs in the Arctic of which 11% are lichens (Callaghan et al. 2004). Despite extreme environ- mental factors including low temperature, intermittent freezing, high intensity of ultraviolet radiation, and pro- longed periods of darkness, lichens are the most successful group among the lower plants and are a successful sym- biosis between a fungus and an alga or a cyanobacterium (Schwendener 1869). It is likely that during the course of evolution, in order to survive in extreme environmental conditions, this symbiosis has provided an effective adap- tation strategy, increasing their chances of survival and dispersal, thereby ensuring their joint colonization and succession in different areas. Extreme conditions of desiccation and irradiation lead to an increase in the formation of reactive oxygen species (ROS). Lichens, however, due to their biochemical char- acters, acquired through symbiosis, have a high tolerance to such environmental stresses (Kranner et al. 2005). They exhibit strong antioxidant and photoprotective mecha- nisms that make them highly resistant to potential damage caused by stress (Kranner and Birtic 2005). Lichens exposed to high intensity of light lower their chlorophyll concentration and produce higher concentrations of photoprotective pigments for non-photosynthetic quench- ing of light energy. Furthermore, they also produce a range of free radical scavengers including glutathione, ascorbate (vitamin C) tocopherol (vitamin E), and phe- nolic secondary products that neutralize the ROS and protect the lichen thallus (Rice-Evans et al. 1996; Kranner et al. 2005). Compounds such as flavonoids, sugars, S. M. Singh (&)  R. Ravindra National Centre for Antarctic and Ocean Research, Vasco-da-Gama, Goa 403 804, India e-mail: smsingh@ncaor.org P. Singh Birla Institute of Technology & Science, Pilani K.K. Birla, Goa Campus, Zuarinagar, Goa 403 726, India 123 Polar Biol (2011) 34:1775–1782 DOI 10.1007/s00300-011-1027-9