Antioxidant properties of various microorganisms isolated from arctic lichen Stereocaulon spp.

Lichens are symbiotic organisms composed of fungi, algae, or cyanobacteria which are able to survive in extreme environmental conditions ranging from deserts to polar areas. Some lichen symbionts produce a wide range of secondary metabolites that have many biological activities such as antibacterial, antifungal, antiviral, antitumor, antioxidant and anti-inflammatory etc. Among the symbionts of lichens, of the bacterial communities of lichen symbionts little is known. In this study, we isolated 4 microbial species from the Arctic lichen Stereocaulon spp. and evaluated their antioxidant properties using 1,1-diphenyl-2-picryl-hydrazyl assay as well as 2,2′-azino-bis(3-ethyl benzothiazoline-6-sulphonic acid) assay. Total phenolic contents and total flavonoid contents were also measured. A potent radical scavenging activity was detected in a number of the lichen extracts. Among the 4 species tested in this study, the ethyl acetate extract of Bosea vestrisii 36546(T) exhibited the strongest free radical scavenging activity, with an inhibition rate of 86.8% in DPPH and 75.2% in ABTS assays. Overall, these results suggest that lichen-bacteria could be a potential source of natural antioxidants.