The In Vitro Antioxidant Properties of Chinese Highland Lichens

The antioxidant properties of 46 lichen species, collected from the highly UV-exposed alpine areas of southwestern China, were evaluated for their potential therapeutic utilization. The anti-linoleic acid peroxidation activity, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) scavenging activity, reducing power, and total phenolic contents were all assessed in vitro in the methanol extract of the lichens. A potent reducing power was detected in a number of the lichen extracts, when compared with butylated hydroxyanisole (BHA). In general, it was found that many of the lichens, with antioxidant properties, contained large quantities of phenolic content. Extracts of Peltigera praetextata and Sticta nylanderiana were found to exhibit the most potent activity in all of the antioxidant tests. In particular, extracts of S. nylanderiana displayed a 1.37 times greater anti-linoleic acid peroxidation activity, when compared with the ascorbic acid used as the positive control. S. nylanderiana also possessed the strongest free radical scavenging activity amongst all the tested species, with an inhibition rate of 90.4% at concentration of $330{\mu}g/ml$. Activity-guided bioautographic TLC and HPLC analyses were used to establish which compounds were responsible for the potent antioxidant activities of the S. nylanderiana extract. These analyses revealed lecanoric acid to be primarily responsible for the effective antioxidant properties of S. nylanderiana. Overall, these results have indicated that several highland lichens have the potential of being utilized as novel bioresources for naturally occurring antioxidant therapies.