Antioxidant and antimicrobial properties of some lichens and their constituents.

The aim of this study is to examine the in vitro antioxidant and antimicrobial activities of the acetone, methanol, and aqueous extracts of the lichens Cladonia furcata (many-forked Cladonia), Hypogymnia physodes (puffed lichen), and Umbilicaria polyphylla (manyleaf navel lichen) and the antimicrobial activity of fumarprotocetraric acid, gyrophoric acid, and physodic acid isolated from the respective lichen species. Antioxidant activity was evaluated by five different methods: free radical scavenging, superoxide anion radical scavenging, reducing power, determination of total phenolic compounds, and determination of total flavonoid content. U. polyphyla exhibited more powerful antioxidant activities than the other lichen species examined: methanol extracts of U. polyphyla showed 90.08% free radical scavenging activities (the ratio was greater than those of standard antioxidants). Moreover, the extracts tested had effective reducing power and superoxide anion radical scavenging. Total contents of phenol and flavonoid in extracts were determined as pyrocatechol equivalents and as rutin equivalents, respectively. A significant strong relationship between total phenolic and flavonoid contents and their antioxidative activities was observed. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method against six species of bacteria and 10 species of fungi. In general, the lichen extracts tested and their respective acids had relatively strong antimicrobial activity against the microorganisms tested. The present study shows that the lichen species tested demonstrated strong antioxidant and antimicrobial activities. The results suggest that lichens may be used as good sources of natural antioxidants and for pharmaceutical purposes in treating various diseases.