Antimicrobial activity of selected corticolous macrolichens
The present study was conducted to screen antimicrobial activity of three foliose macrolichens viz., Parmotrema reticulatum (Taylor) M. Choisy (Parmeliaceae), Heterodermia obscurata (Nyl.) Trevis (Physciaceae) and Dirinaria consimilis (Stirt.) D.D. Awasthi (Physciaceae) and two fruticose macrolichens viz., Ramalina pacifica Asahina (Ramalinaceae), and Ramalina hossei H. Magn & G. Awasthi (Ramalinaceae) growing on barks of areca trees. The lichens were identified on the basis of morphological, anatomical and color tests and the secondary metabolites (lichen substances) were identified by thin layer chromatography. Antibacterial activity of lichen extracts was evaluated against three Gram positive and five Gram negative bacteria by Agar well diffusion assay. The lichen extracts were effective in inhibiting all test bacteria. Overall, extract of D. consimilis and P. reticulatum displayed marked and least antibacterial efficacy. Marked inhibitory activity was observed against Klebsiella pneumoniae. Antifungal effect of lichen extracts was determined against four molds by Poisoned food technique. Among fungi, the growth of Colletrotrichum capsici was suppressed to higher extent by lichen extracts. The observed inhibitory activity of lichens could be ascribed to the presence of lichen substances.
Keywords: Lichens, Antimicrobial, Agar well diffusion, Poisoned food technique