Screening the antioxidant and antimicrobial properties of the lichens Parmelia saxatilis, Platismatia glauca, Ramalina pollinaria, Ramalina polymorpha and Umbilicaria nylanderiana.

The aim of this study is to investigate in vitro antimicrobial and antioxidant activities of the methanol extracts of Parmelia saxatilis (L) Ach., Platismatia glauca (L.) W.L. Club. & C.F. Culb., Ramalina pollinaria (Wesstr.) Ach., Ramalina polymorpha (Liljeblad) Ach. and Umbilicaria nylanderiana (Zahlbr.) H. Magn. Antioxidant activity was evaluated by two separate methods: scavenging of free radical DPPH and the inhibition of linoleic acid oxidation. Extracts of Parmelia saxatilis, Platismatia glauca., Ramalina pollinaria and Ramalina polymorpha did not exert any activity in both assays, whereas those of Umbilicaria nylanderiana provided 50% inhibition at 400.2 microg/ml concentration in the former and gave 53% inhibition at 2g/l concentration. Total phenolic constituents of extracts from lichen species tested (P. saxatilis, P. glauca, R. pollinaria, R. polymorpha and U. nylanderiana) were 1.0% (w/w), 1.1% (w/w), 1.0% (w/w), 0.8% (w/w) and (3.0% w/w), respectively (as gallic acid equivalent); implying that the observed activity could be related to the amount of polar phenolics. Extracts were also found to possess antimicrobial activity against some test bacteria and fungi and yeast.