Investigation of Antimicrobial and Antioxidant Activities of some Lichens

This study investigated the antimicrobial and antioxidant properties of methanol extracts from five lichen species: Polycauliona candelaria (Syn. Xanthoria candelaria), Nephromopsis chlorophylla (Syn. Cetraria chlorophylla), Circinaria calcarea (Syn. Aspicilia calcarea), Bryoria capillaris (Syn. Alectoria cana), and Peltigera canina (Syn. Dermatodea canina). Antimicrobial activities were determined using the agar disc diffusion method, while minimal inhibitory concentration (MIC) values were determined using the micro-well dilution method. Among the lichen species, methanol extract of Circinaria calcarea exhibited the highest antimicrobial activity, with a 15 mm zone of inhibition against Escherichia coli and Bacillus cereus. It also demonstrated the lowest MIC value (31.25 μg/mL) against Bacillus cereus, Bacillus subtilis, Clostridium perfringens and Escherichia coli were the most sensitive microorganisms to lichens. Various antioxidant determination methods were employed to assess the antioxidant activities of the lichens, including ferric ion (Fe+3) reduction capacity, cupric ion (Cu+2) reduction capacity, ferric ion reducing antioxidant power (FRAP), DPPH radical scavenging activity, DMPD radical scavenging activity and metal chelating activity using the bipyridyl reagent. All lichens exhibited excellent antioxidant activity, particularly in metal chelating activity using the bipyridyl reagent. Peltigera canina demonstrated the highest antioxidant activity among the studied lichen species across most of the applied method.