Antioxidant and antibacterial properties of some cultured lichens.

The lichen species namely Usnea ghattensis, Heterodermia podocarpa, Arthothelium awasthii and Parmotrema tinctorum have been cultured in vitro and were screened for their antioxidant and antibacterial potential using different assay systems. The methanol extract of lichens showed antioxidant and antibacterial activities according to the order U. ghattensis>A. awasthii>H. podocarpa>P. tinctorum. The IC(50) values for the antioxidant activities of U. ghattensis and A. awasthii are less or equivalent to that of standard antioxidants. The methanolic extracts of the mycobiont and photobiont cultures of lichenU. ghattensis and A. awasthii were effective against Bacillus licheniformis, Bacillus megaterium, Bacillus subtilis and Staphylococcus aureus. The minimum inhibitory concentration (MIC) of the extract was found between 5 and 10microg extract/ml. The results suggested that the extract of mycobiont and photobiont cultures of lichen U. ghattensis and A. awasthii could be of use as an easily accessible source of natural antioxidants and antibacterial properties for the possible food supplement or in the pharmaceutical industry.

Tissue culture of some lichens and screening of their antioxidant, antityrosinase and antibacterial properties.

Lichen species Usnea ghattensis, Heterodermia podocarpa, Arthothelium awasthii and Parmotrema tinctorum have been cultured in vitro and screened for their antioxidant, antimicrobial and antityrosinase potential using different assay systems. The methanol extract of lichens showed antioxidant, antimicrobial and antityrosinase activities according to the order Usnea ghattensis > Arthothelium awasthii > Heterodermia podocarpa > Parmotrema tinctorum. The IC(50) values for the antioxidant and antityrosinase activities of U. ghattensis and A. awasthii were less than or equivalent to that of standard antioxidants and tyrosinase inhibitors. The methanol extracts of the lichen cultures Usnea ghattensis and Arthothelium awasthii were effective against Bacillus licheniformis, Bacillus megaterium, Bacillus subtilis and Staphylococcus aureus. The minimum inhibitory concentration (MIC) of the extract was found to be between 5 and 10 microg extract/mL. The results suggested that the extract of lichen cultures, U. ghattensis and A. awasthii, could be of use as an easily accessible source of natural antioxidants, tyrosinase inhibitory and antimicrobial properties as possible food supplements or in the pharmaceutical industry.

Experimental studies on the growth and usnic acid production in "lichen"Usnea ghattensis in vitro.

The study was aimed to optimize the culture conditions for the production of usnic acid in the cultured cell aggregates composed of symbionts in lichen Usnea ghattensis in vitro. The cultured lichen tissue composed of symbionts appeared after about 2-3 weeks of inoculation in water-agar and malt-yeast extract (MYE) media and shown the production of usnic acid after 2-3 months of inoculation. However, the growth of symbionts was strongly affected by different culture conditions. The addition of excess carbon and nitrogen sources in the media has significantly enhanced the growth as well as usnic acid content. The cultured symbionts in MYE medium having 4% sucrose, 4% polyethyl glycol (PEG) gave 7.63 g dry biomass with 3.9 microg usnic acid/g dry biomass. In water-agar medium having 4% sucrose and 4% PEG gave 3.08 g dry biomass with 1.11 microg usnic acid/g dry biomass. The positive effects of medium on the growth of symbionts and the production of usnic acid are seemed to be due to nutritional factors.

Antioxidant and antibacterial activities of lichen Usnea ghattensis in vitro.

Various solvent extracts of the lichen Usnea ghattensis showed good antioxidant activity. A methanol extract prevented lipid peroxidation by 87% followed by 65% in Trolox at 20 microg/ml. It also showed superoxide anion scavenging activity and free radical scavenging activity 56% and 73%, respectively. The known antioxidants butylated hydroxytoluene (BHT), butylated hydroxyanisol (BHA) and quercetin at similar concentrations showed superoxide anion scavenging activity of 68, 59 and 47% and free radical scavenging activity 83, 77 and 69%, respectively. In addition, these extracts were inhibitory against Bacillus licheniformis, Bacillus megaterium, Bacillus subtilis and Staphylococcus aureus with MIC values of 5-10 microg/ml.

Evaluation of antioxidant potential of the cultured mycobiont of a lichen Usnea ghattensis.

The biologically active compounds, antioxidant activities and free radical scavenging effects of dry matter of cultural medium (DMCM), filtrate (DMF) and different solvent extracts of mycobiont from lichen species Usnea ghattensis in submerged culture (UGSC) were investigated. DMF showed the strongest inhibition of lipid peroxidation as a function of its concentration, and was comparable to the antioxidant activity of BHA at the same concentration of 0.2 mg/mL. The hexane extract of mycobiont had the weakest antioxidant ability, whereas other mycobiont extracts exhibited a modest to strong inhibition of lipid peroxidation and in free radical scavenging activity. The antioxidant activities of mycobiont extracts were correlated with the presence of total polyphenol content in the extract. It was found that antioxidant components in methanol, acetone, ethanol and hexane extracts must be derived from the secondary metabolites produced by the lichen mycobiont. The results presented herein indicate that extracts of cultured mycobiont of lichen Usnea ghattensis could possibly act as chemopreventing agent with respect to free radical-related diseases.