In vitro risk assessment of usnic acid.

Lichens are symbiotic organisms composed of fungi and algae and are very common in Turkey. Lichen secondary metabolites are mainly phenolic compounds produced by fungal partner of lichen symbiosis. Usnic acid (UA) is one of the most common lichen metabolites, and it was reported that to be effective for a wide range of pharmacological purposes including antiviral, antitumor, and antiprotozoal. However, there are limited data on the genotoxic and antioxidant effects of UA in cultured human peripheral blood cells. Therefore, the aim of this thesis study was to investigate the genetic and oxidative effects of UA in cultured human blood cells (n = 5). The UA was added into culture tubes at various concentrations (0-200 µg/ml). Chromosomal aberrations (CA) and micronuclei (MN) tests were performed for genotoxic damage influences estimation. In addition, biochemical parameters (total antioxidant capacity (TAC) and total oxidative status (TOS)) were examined to determine oxidative effects. In our in vitro test systems, it was observed that UA had no mutagenic effects on human lymphocytes. Furthermore, our results indicated that low concentrations (1 and 5 µg/ml) of UA caused increases of TAC levels in cultured human blood cells. And, the TOS levels were not changed (p > 0.05) when all the concentrations (except for 200 µg/ml) of UA were applied. In conclusion, UA can be a new resource of therapeutics as recognized in this study with their nonmutagenic and antioxidant features.

Genotoxic, antigenotoxic and antioxidant properties of methanol extracts obtained from Peltigera horizontalis and Peltigera praetextata.

Now-a-days, there is a big need to reduce genotoxic effects of mutagenic and carcinogenic agents in environment, which are increased by the technological development. Lichens produce a wide variety of unique metabolites due to being in various extreme areas and being symbiotic organisms of fungi and algae. Therefore, this study was planned to search new sources having antimutagenic activity by researching two different lichen species and to determine whether their usage is safe. With this respect, the mutagenic and antimutagenic properties of methanol extracts of the lichens were determined by the bacterial reverse mutation and sister chromatid exchange assays. Furthermore, the malondialdehyde level, superoxide dismutase, glutathione and glutathione peroxidase activities against aflatoxin B1 were determined for understanding the ways in which the lichens showed their genotoxic properties.

Genotoxic and antigenotoxic assessment of four newly synthesized dihydropyridine derivatives.

The current study aims to determine the genotoxic and antigenotoxic potential of four newly synthesized dihydropyridine derivatives using Escherichia coli WP2 and Ames/Salmonella bacterial reversion assay systems. The bacterial mutant tester strains, E. coli WP2uvrA with a point mutation and Salmonella typhimurium TA1537 with a frameshift mutation, were used to determine genotoxic potentials of the test compounds. To determine antigenotoxic potentials of the test compounds, the same strains were also used together with positive mutagens N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) for E. coli WP2uvrA and 9-aminoacridine (9-AA) for S. typhimurium TA1537. According to the results, neither of the test compounds showed significant genotoxic activity on both tester strains at the tested concentrations. However, except compound 4, all the test compounds showed significant antigenotoxic activity on MNNG- or/and 9-AA-induced mutations. The inhibition rates of mutagenesis ranged from 27.0% (compound 2: 2.5 mM/plate) to 65.0% (compound 2: 0.5 mM/plate) for MNNG and from 30.6% (compound 2: 2 mM/plate) to 58.5% (compound 1: 1 mM/plate) for 9-AA genotoxicity. According to these results, it is concluded that all the test compounds do not have a mutagenic potential on the bacterial strains at the tested concentrations, and some of them have antigenotoxic potentials against MNNG- and 9-AA-induced mutagenesis.