Antimicrobial activity of Heterodermia incana (Stirt.) D.D. Awasthi

H. L. Raghavendra


Objectives: Lichens represent one of the most successful symbiotic interactions and are formed from a photobiont and a mycobiont. The foliose lichen genus Heterodermia is one of the cosmopolitan lichen genera. The present study was conducted to investigate antibacterial and antifungal activity of Heterodermia incana (Stirt.) D.D. Awasthi, a foliose macrolichen belonging to the family Physciaceae. Materials and Methods: Extraction of dried and powdered lichen was carried out by maceration process. Antibacterial activity of the extract was evaluated against 2 Gram-positive and 2 Gram-negative bacteria by agar well diffusion assay. Antifungal activity of extract was determined against 3 seedborne fungi by poisoned food technique. Results: Extract was effective in inhibiting the growth of all test bacteria in a concentration dependent manner with marked activity against Gram-positive bacteria. Bacillus cereus (zone of inhibition 2.26 ± 0.05 cm) and Pseudomonas aeruginosa (zone of inhibition 1.76 ± 0.05 cm) were inhibited to higher extent among Gram-positive and Gram-negative bacteria, respectively, at 10 mg/ml extract concentration. The extract was effective in inhibiting the mycelial growth of test fungi in a concentration dependent manner. Among three fungi, the susceptibility to extract was in the order: Fusarium sp. > Curvularia sp. > Alternaria sp. At extract concentration 1 mg/ml, >60% inhibition of all test fungi was observed. Conclusion: The lichen H. incana is a promising resource of antimicrobial agents. The observed bioactivities could be attributed to the presence of secondary metabolites such as atranorin and zeorin present in the extract. In suitable form, the lichen can be used as anti-infective agent and in the management of seedborne fungal diseases.

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