In the present study, the biosynthesis of silver nanoparticles was carried out by four types of lichen biomasses through in vitro culture. The synthesized silver nanopartilces were characterized by U.V visible spectroscopy, Scanning Electron microscopy, Fourier Transform Infrared Spectroscopy. The in vitro antibacterial activities of the biosynthesized nanopartilces have been evaluated by disk diffusion method against both gram positive and negative laboratory test organisms. The silver nanoparticles were tested for their in vitro antioxidant activity includes Free Radical Scavenging Activity by DPPH, Reducing power by Oyaizu method, Determination of the Total Phenols by Folin-Ciocalteau method and Total Antioxidant Capacity by phosphomolybdenum method. The biosynthesized silver nanopartilces from 4 types of lichens having particle sizes ranging from 150-250 nm at maximum absorption of 400-450 nm on U.V-visible spectroscopy with different types of functional groups. The antibacterial activity of silver nanoparticles synthesizes from Evernia mesomorpha shows maximum activity on gram negative bacteria. The in vitro total antioxidant activity, free radicle scavenging activity and lipidperoxidase activity of silver nanoparticles synthesizes from Punctelia subrudecta (3 35 ± 0 04, 34 48 ± 1 19, 73 45 ± 1 3) found to have more activity than the remaining samples. In the case of total phenolic compounds Parmeliopsis ambigua shows significant more activity (14 89 ± 0 78) than the remaining samples. In conclusion, the results demonstrated that the synthesis of bioactive silver nanoparticles from lichens were found to have higher antibacterial activity and antioxidant capacity and may be used as potential scavenger.
Lichens are an association of a photobiont (an alga or a cyanobacterium) and a mycobiont (a fungus). The lichen genus Ramalina is one of the cosmopolitan lichen genera and is characterized by fruticose thallus. In the present study, an antibacterial and antifungal activity of an extract of three Ramalina species (Ramalinaceae) viz. R. hossei Vain, R. conduplicans Vain and R. pacifica Asahina obtained by maceration process were investigated. The lichens were collected from different places of Shivamogga district, Karnataka, India and identified on the basis of morphological, anatomical and chemical tests. The antibacterial and antifungal activity of lichen extracts was carried out by Agar well diffusion and Poisoned food technique respectively. Overall, B. cereus and E. coli were inhibited to higher extent and least extent respectively by extracts of Ramalina species. R. pacifica and R. hossei inhibited bacteria to highest and least extent respectively. In the case of antifungal activity, marked and least inhibitory activity was shown by an extract of R. hossei and R. pacifica respectively. Among fungi, Alternaria sp. and Fusarium sp. were inhibited to highest and least extent respectively. The observed antimicrobial potential could be ascribed to the presence of secondary metabolites such as usnic acid, salazinic acid and sekikaic acid present in the Ramalina species.
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