Antimicrobial Activity of Ramalina conduplicans Vain. (Ramalinaceae)

Abstract

The members of the genus Ramalina (Ramalinaceae) are fruticose lichens growing on various types of substrata. The present study was conducted with an aim of determining antimicrobial activity of Ramalina conduplicans Vain. The powdered lichen material was extracted sequentially using petroleum ether, ethyl acetate and ethanol. The solvent extracts were screened for antibacterial activity by Agar well diffusion assay against 15 bacteria which included reference strains and isolates from burn, dental caries and urinary tract infections. Poisoned food technique was performed to determine antifungal effect of solvent extracts against fungal isolates from anthracnose of chilli, foot rot of finger millet and mouldy grains of sorghum. Usnic acid, Salazinic acid and Sekikaic acid were detected in the lichen. The solvent extracts were shown to exhibit dose dependent inhibitory activity against test bacteria. Ethyl acetate extract inhibited reference bacterial strains to higher extent. Among solvent extracts, only ethanol extract inhibited all urinary tract bacteria. S. aureus isolates from burn were inhibited to higher extent when compared to S. mutans isolates from dental caries. The solvent extracts exhibited varied inhibitory activity against test fungi. Ethyl acetate extract inhibited Alternaria sp., Aspergillus flavus and Sclerotium rolfsii to higher extent while Colletotrichum capsici and Helminthosporium sp. were inhibited to higher extent by petroleum ether and ethanol extract respectively. The observed inhibitory potential of solvent extracts of R. conduplicans could be ascribed to the presence of secondary metabolites. The lichen can be used in the treatment of bacterial infections and to manage plant pathogenic fungi.

Keywords: i Antimicrobial Agar well diffusion Poisoned food technique