Free radicals play a critical role in the chemical processes that occur in all cells. Pharmaceutical companies manufacture a variety of synthetically prepared antioxidants, but it is known that many of these can be carcinogenic. As a result, efforts are being made to find natural antioxidants that do not have these side effects. Lichens may be suitable candidates because they contain secondary metabolites with proven antioxidant properties. This could be explained by the presence of compounds with phenolic groups in lichens. The radical scavenging reaction is a chemical reaction governed by stoichiometry, and our aim is to determine the efficacy of these reactions. The aim of this study is to compare metabolite activity based on the same amount of substance involved in radical scavenging, calculated in micromoles rather than weight concentration. This provides an accurate way of comparing radical scavenging activity. We tested superoxide anion scavenging activity and free radical scavenging activity of isolated lichen secondary metabolites and their mixtures in different ratios. The following compounds were isolated and tested for antioxidant activity: gyrophoric acid (Umbilicaria hirsuta), evernic acid (Evernia prunastri), physodic acid, 3-hydroxyphysodic acid, physodalic acid and atranorin (Hypogymnia physodes), and usnic acid (as a synthetic compound). Of all the tested compounds, 3-hydroxyphysodic acid, as well as mixtures containing this metabolite, showed the strongest scavenging activity. The results also demonstrated that calculation by amount of substance leads to a new consideration of antioxidant activity.

The desiccation tolerant moss Hedwigia ciliata was investigated to assess its early reaction to water stress in controlled conditions. Thus, various photosynthetic parameters and water contents were studied during a selected time frame within 48 h of two main events, namely water loss after full hydration and activity (preparation for anabiosis) and water uptake after the state of anabiosis. The observations of the changes in the photosynthetic efficiency of Hedwigia ciliata in response to fluctuating relative water contents (RWCs) during rehydration and dehydration periods provide valuable insights into the species’ physiological adaptation mechanisms. Hedwigia ciliata rapidly uptakes water upon anabiosis, and despite being poikilohydric, it is able to retain water for a prolonged period compared to the water availability in its immediate environment. The delayed decrease in relative water content (RWC) corresponds to the photosynthetic parameters and preparation for anabiosis, including the maintenance of photosystems and general cell integrity. The low values of non-photochemical quenching during desiccation imply limited photoinhibition and effective photoprotective regulation. Conversely, the rather high values of the fluorescence decline ratio during rehydration reflect the efficient recovery of photosynthetic performance. The postponed physiological shutdown while drying and photosynthetic activity in the early dehydration phase suggest anticipatory acclimation to desiccation, i.e., non-active phase anabiosis. Hedwigia ciliata is a desiccation-tolerant moss, with anatomical, morphological, and eco-physiological adaptations, making it a useful model species in drought and abiotic stress studies of bryophytes in a rapidly changing environment.

Cyanobacterium Nostoc commune is a filamentous terrestrial prokaryotic organism widely distributed, which suggest its high adaptive potential to environmental or abiotic stress. Physiological parameters and proteomic analysis were performed in two accession of N. commune with the aim to elucidate the differences of physiological trails between distant geotypes, namely Antarctic (AN) and central European (CE). The result obtained clearly showed that the AN geotype demonstrates elevated levels of total phenols, flavonoids, carotenoids, and phycobiliproteins, indicative of its adaptation to environmental stress as referred by comparison to CE sample. Additionally, we employed LC-MS analysis to investigate the proteomes of N. commune from AN and CE geotypes. In total, 1147 proteins were identified, among which 646 proteins expressed significant (up-regulation) changes in both accessions. In the AN geotype, 83 exclusive proteins were identified compared to 25 in the CE geotype. Functional classification of the significant proteins showed a large fraction involved in photosynthesis, amino acid metabolism, carbohydrate metabolism and protein biosynthesis. Further analysis revealed some defense-related proteins such as, superoxide dismutase (SOD) and glutathione reductase, which are rather explicitly expressed in the AN N. commune. The last two proteins suggest a more stressful condition in AN N. commune. In summary, our findings highlight biochemical processes that safeguard the AN geotype of N. commune from extreme environmental challenges, not recorded in CE accession, probably due to less stressful environment in Europe. This study brings the first ever proteomic analysis of N. commune, emphasizing the need for additional investigations into the climate adaptation of this species with rather plastic genome.