Comparative analysis of antimicrobial, antioxidant activities and phytochemicals of Himalayan lichens

The aim of the present study is to investigate the antimicrobial and antioxidant activities of lichens collected from Himalaya and to analyze their phytochemicals. Twelve species of lichens investigated in the present study are Cladonia rangiferina , Everniastrum cirrhatum , Flavoparmelia caperata , Lobaria retigera , Nephromopsis nephromoides , Parmotrema nilgherrense , Ramalina conduplicans , Ramalina sinensis , Stereocaulon foliolosum , Usnea longissima , Usnea orientalis and Usnea pangiana . The metabolites of lichens were extracted from acetone, ethyl acetate, chloroform and methanol solvents. The antimicrobial activities were tested against bacteria and fungi at 2 mg/ml concentration. The most active acetone and chloroform extracts of R. conduplicans showed the highest inhibition zone of 22.7 ± 0.2 and 23.3 ± 0.2 mm respectively against Acinetobacter baumannii . The methanol extract of U. longissima showed the maximum inhibitory activity (15.2 ± 2.5 mm) against P. aeruginosa . The principal component analysis of different lichen extracts complimented the result observed for antibacterial activities for various extracts. Usnea longissima showed strong antioxidant activity with IC 50 of free radical scavenging activities 116.24 ± 1.8 µg/ml. The Usnea species exhibited the maximum contents of phytochemicals that may be responsible for antioxidant activities. Acetone and chloroform extracts of R. conduplicans and methanol extract of U. longissima were subjected to GC–MS. In the present study, GC–MS revealed that 4,6-diamino-O-cresol was at highest concentration of 75.37% in acetone extract, followed by 51.53% of methoxy benzyl alcohol in chloroform extract of R. conduplicans and benzoic acid, 2-hydroxy-4-methoxy-6-methyl-, methyl ester that was 44.5% in methanol extract of U. longissima. The presence of various compounds in extracts may be responsible for excellent bioactivities exhibited by the lichen.