Metabolomic Profile and Functional State of Oat Plants (Avena sativa L.) Sown under Low-Temperature Conditions in the Cryolithozone.

Oats are one of the most useful and widespread cereal crops in the world. In permafrost conditions (Central Yakutia), based on metabolic changes in late summer-sown oat plants (Avena sativa L.), the key processes involved in the cold acclimation of a valuable cereal species were identified. During the onset of low ambient temperatures, metabolites from leaf samples were profiled using gas chromatography with mass spectrometry (GC-MS) and were analyzed using principal component analysis (PCA). A total of 41 metabolites were identified in oat leaves. It was found that acclimation to suboptimal temperatures during the fall period leads to biochemical (accumulation of mono- and disaccharides and decrease in fatty acids and polyols) as well as physiological and biophysical changes (decrease in leaf PRI reflectance indices and chlorophyll a fluorescence). Therefore, the study contributes to a more holistic understanding of oat metabolism under low-temperature cryolithozone stress. It is believed that the analysis of changes in leaf reflection properties and JIP-test parameters of chlorophyll a fluorescence using leaf metabolomic profiling can be used in the selection of valuable varieties of cereal crops to obtain plant fodders with high nutrient contents under conditions of a sharply continental climate.

Antioxidant and cytotoxic activities of quinones from Cetraria laevigata.

Chemical investigation of the extracts obtained from the red thallus tips from Cetraria laevigata resulted in the isolation of five known quinoid pigments identified by FT-IR, UV, NMR, MS methods and by comparison with literature data (skyrin (1), 3-ethyl-2,7-dihydroxynaphthazarin (2), graciliformin (3), cuculoquinone (4) and islandoquinone (5)). An antioxidant capacity of compounds 1-5 were evaluated and compared with quercetin using a lipid peroxidation inhibitory assay and superoxide radical (SOR), nitric oxide radical (NOR), 1,1-diphenyl-2-picrylhydrazine (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) scavenging assays. Compounds 2, 4 and 5 were far more active: they demonstrated the antioxidant capacity in various test assays with the IC50 values 5-409 µM comparable to the flavonoid quercetin. While, the isolated quinones (1-5) exhibited weak cytotoxicity in human cancer cell line A549 assessed by MTT assay.

Do epiphytic lichens negatively impact their hosts through allelopathy? The effect of Evernia esorediosa on growth and biochemical processes of Larix gmelinii.

The question of the nature of the interaction between epiphytic lichens and their host trees remains highly debated. Some authors showed cases of allelopathy, but this needs further investigation. Our study covers the effects caused by the epiphytic lichen Evernia esorediosa (Müll. Arg.) Du Rietz on growth and biochemical processes in Larix gmelinii (Rupr.) Rupr. ex Kuzen trees in cryolithozone boreal forests. Usnic acid (UA) is shown to migrate from the thalli of E. esorediosa in the bark and phloem of L. gmelinii, from which it is transported to the root system of the tree, and then UA is moved upward through the xylem into tree needles. Accumulation of UA in L. gmelinii needles causes the following effects: inhibition of photosynthesis, cellular respiration and oxidative phosphorylation. These disruptions could reflect on the tree growth processes. The L. gmelinii trees inhabited by the epiphytic lichen E. esorediosa were found to show lower radial and apical growth parameters. Our results show that E. esorediosa exhibits an allelopathic effect toward L. gmelinii through the migration of UA from the lichen thalli to the tissues of the tree, which led to inhibition of energetic processes in cells. This caused the tree growth to slow down and could ultimately lead to its death.

Genotoxicity of (+)- and (-)-usnic acid in mice.

Usnic acid, which is the most widespread and well-studied secondary lichen compound, has antibacterial and cytotoxic effects. Usnic acid is present in lichens as the (+)- and (-)-enantiomers, which have different biological activities. We used a DNA-comet assay to determine the genotoxic effect of (+)- and (-)-usnic acid in the liver and kidney cells of mice. The genotoxic effect of usnic acid was only observed 1 h after oral administration. Usnic acid doses of 100 and 50 mg/kg resulted in DNA damage in the liver and kidney cells. The genotoxic effect of usnic acid is associated with oxidative stress in cells. There were no significant differences in the effects of (+)- and (-)-enantiomers.