Chemistry of the lichen Hypogymnia physodes transplanted to an industrial region

Lichen as Bioindicators: Assessing their Response to Heavy Metal Pollution in Their Native Ecosystem

Lichens play crucial roles in the ecosystems, contributing to soil formation and nutrient cycling, and being used in biomonitoring efforts to assess the sustainability of ecosystems including air quality. Previous studies on heavy metal accumulation in lichens have mostly relied on manipulated environments, such as transplanted lichens, leaving us with a dearth of research on how lichens physiologically respond to heavy metal exposure in their natural habitats. To fill this knowledge gap, we investigated lichens from two of South Korea's geographically distant regions, Gangwon Province and Jeju Island, and examined whether difference in ambient heavy metal concentrations could be detected through physiological variables, including chlorophyll damage, lipid oxidation, and protein content. The physiological variables of lichens in response to heavy metals differed according to the collection area: Arsenic exerted a significant impact on chlorophyll degradation and protein content. The degree of fatty acid oxidation in lichens was associated with increased Cu concentrations. Our research highlights the value of lichens as a bioindicator, as we found that even small variations in ambient heavy metal concentrations can be detected in natural lichens. Furthermore, our study sheds light on which physiology variables that can be used as indicators of specific heavy metals, underscoring the potential of lichens for future ecology studies.

Distribution Types of Lichens in Hungary That Indicate Changing Environmental Conditions

Simple Summary

As the occurrences of lichens are strongly correlated to background environmental conditions (e.g., air pollution, global warming), the analysis of their distribution has a great value for bioindication. Distribution data are originating from earlier herbarium collections, recent field and literature studies. The distribution analyses in lichen species with different ecological requirements allowed comparisons and showed clear trends. Five distribution types were introduced—presented by characteristic examples—according to lichen distribution maps prepared in different periods of time (representing changing environmental conditions): (1) species of decreasing occurrences by time (acidic pollution sensitive species), (2) species with no or few former records but with increasing occurrences in recent decades (sub-Mediterranean species), (3) species with increasing and then (from c. 2000) decreasing occurrences (acidofrequent species), (4) species with widely increasing occurrences in recent decades (nitrofrequent species), and (5) species with rapidly increasing occurrences (rapidly spreading species of uncertain reasons). The discussed trends are known for some species at a global scale or European level, other examples are characteristic for Central Europe or Hungary. By studying the distribution maps of lichen bioindicators, tendencies of climate change and type of pollution can be determined and further changes can be predicted.

Abstract

Distribution data originating from earlier herbarium collections and recent biodiversity records form the basis of distribution analyses in lichen species with different ecological requirements, where the records allowed comparisons or showed clear trends. As the occurrences of lichens are strongly correlated to background environmental conditions (e.g., air pollution, global warming), confirmed by Wirth’s ecological indicator values, the analysis of distribution types has a great value for bioindication and the establishment of current and future climatic and pollution situations. Five distribution types were introduced—presented by characteristic examples (13)—according to lichen distribution maps prepared in different periods of time (representing changing environmental conditions): (1) species of decreasing occurrences by time (e.g., Lobaria pulmonaria, Menegazzia terebrata, suboceanic, acidic pollution sensitive species), (2) species with no or few former records but with increasing occurrences in recent decades (e.g., Flavoparmelia soredians, Hyperphyscia adglutinata, Solenopsora candicans, sub-Mediterranean species), (3) species with increasing and then (from c. 2000) decreasing occurrences (e.g., Scoliciosporum chlorococcum, Straminella conizaeoides, acidofrequent species), (4) species with widely increasing occurrences in recent decades (e.g., Physcia aipolioides, Piccolia ochrophora, Xanthoria parietina, nitrofrequent species), and (5) species with rapidly increasing occurrences (e.g., Absconditella lignicola, Coenogonium pineti, Evernia divaricata, rapidly spreading species). The proposed distribution types of lichen species may be applied to wider regions (the European or the global level).

Elemental Analysis and In Vitro Evaluation of Antibacterial and Antifungal Activities of Usnea barbata (L.) Weber ex F.H. Wigg from Călimani Mountains, Romania

This study aims to complete our research on Usnea barbata (L.) Weber ex F.H. Wigg (U. barbata) from the Călimani Mountains, Romania, with an elemental analysis and to explore its antibacterial and antifungal potential. Thus, we analyzed twenty-three metals (Ca, Fe, Mg, Mn, Zn, Al, Ag, Ba, Co, Cr, Cu, Li, Ni, Tl, V, Mo, Pd, Pt, Sb, As, Pb, Cd, and Hg) in dried U. barbata lichen (dUB) by inductively coupled plasma mass spectrometry (ICP-MS). For the second study, we performed dried lichen extraction with five different solvents (ethyl acetate, acetone, ethanol, methanol, and water), obtaining five U. barbata dry extracts (UBDE). Then, using an adapted disc diffusion method (DDM), we examined their antimicrobial activity against seven bacterial species-four Gram-positive (Staphylococcus aureus, Enterococcus casseliflavus, Streptococcus pyogenes, and Streptococcus pneumoniae) and three Gram-negative (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa)-and two fungi species (Candida albicans and Candida parapsilosis). Usnic acid (UA) was used as a positive control. The ICP-MS data showed a considerable Ca content (979.766 µg/g), followed by, in decreasing order, Mg, Mn, Al, Fe, and Zn. Other elements had low levels: Ba, Cu, Pb, and Cr (3.782-1.002 µg/g); insignificant amounts (<1 µg/g) of Hg and V were also found in dUB. The trace elements Ag, As, Cd, Co, Li, Tl, Mo, Pd, Pt, and Sb were below detection limits (<0.1 µg/g). The DDM results-expressed as the size (mm) of the inhibition zone diameter (IZs)-proved that the water extract did not have any inhibitory activity on any pathogens (IZs = 0 mm). Gram-positive bacteria displayed the most significant susceptibility to all other UBDE, with Enterococcus casseliflavus showing the highest level (IZs = 20-22 mm). The most susceptible Gram-negative bacterium was Pseudomonas aeruginosa (IZs = 16-20 mm); the others were insensitive to all U. barbata dry extracts (IZs = 0 mm). The inhibitory activity of UBDE and UA on Candida albicans was slightly higher than on Candida parapsilosis.

Metabolic processes involved with sugar alcohol and secondary metabolite production in the hyperaccumulator lichen Diploschistes muscorum reveal its complex adaptation strategy against heavy-metal stress

The synthesis of various unique secondary metabolites by lichens is the result of mutualistic symbiotic association between the mycobiont and autotrophic photobiont. The function of these compounds and causal factors for their production are not fully understood. This paper examines the effect of heavy-metal bioaccumulation and physiological parameters related to photosynthesis and carbon metabolism on the production of lichen substances in hyperaccumulator Diploschistes muscorum. The obtained model of secondary metabolite concentrations in the thalli demonstrates that the carbon source provided by the photobiont and associated polyols produced by the mycobiont have positive impact on the production; on the contrary, the increased intracellular load of heavy metals and excessive loss of cell membrane integrity adversely affected secondary metabolite contents. Additionally, the production of secondary metabolites appears to be more dependent on intracellular metal concentrations than on soil pollution level. To compensate for metal stress, both efficient functioning of algal component and sufficient production of secondary metabolites are required. The balanced physiological functioning of mycobiont and photobiont constitutes the complex protective mechanism to alleviate the harmful effects of heavy metal stress on primary and secondary metabolism of lichens.

Permeability of Hypogymnia physodes Extract Component-Physodic Acid through the Blood-Brain Barrier as an Important Argument for Its Anticancer and Neuroprotective Activity within the Central Nervous System

Simple Summary

Central nervous system (CNS) diseases, including tumors such as glioblastomas and neurodegenerative diseases, such as Alzheimer’s disease, are some of the greatest challenges of modern medicine. Therefore, our study aimed to evaluate the anticancer and neuroprotective activity of the extract from a common European lichen Hypogymnia physodes and of its compound-physodic acid. The examined substances were cytotoxic against the glioblastoma cell lines A-172, T98G, and U-138 MG. Both substances strongly inhibited hyaluronidase, and diminished cyclooxygenase-2 activity (H. physodes extract), enzymes expressed in patients with malignant glioma. Furthermore, H. physodes extract inhibited tyrosinase activity, the enzyme linked to neurodegenerative diseases. The tested substances exhibited antioxidant activity, however, acetylcholinesterase and butyrylcholinesterase inhibitory activity were not high. We proved that physodic acid can cross the blood–brain barrier. We conclude that physodic acid and H. physodes extract should be regarded as promising agents with anticancer, chemopreventive, and neuroprotective activities, especially concerning CNS.

Abstract

Lichen secondary metabolites are characterized by huge pharmacological potential. Our research focused on assessing the anticancer and neuroprotective activity of Hypogymnia physodes acetone extract (HP extract) and physodic acid, its major component. The antitumor properties were evaluated by cytotoxicity analysis using A-172, T98G, and U-138 MG glioblastoma cell lines and by hyaluronidase and cyclooxygenase-2 (COX-2) inhibition. The neuroprotective potential was examined using COX-2, tyrosinase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) activity tests. Moreover, the antioxidant potential of the tested substances was examined, and the chemical composition of the extract was analyzed. For physodic acid, the permeability through the blood–brain barrier using Parallel Artificial Membrane Permeability Assay for the Blood–Brain Barrier assay (PAMPA-BBB) was assessed. Our study shows that the tested substances strongly inhibited glioblastoma cell proliferation and hyaluronidase activity. Besides, HP extract diminished COX-2 and tyrosinase activity. However, the AChE and BChE inhibitory activity of HP extract and physodic acid were mild. The examined substances exhibited strong antioxidant activity. Importantly, we proved that physodic acid crosses the blood–brain barrier. We conclude that physodic acid and H. physodes should be regarded as promising agents with anticancer, chemopreventive, and neuroprotective activities, especially regarding the central nervous system diseases.

Spider Webs and Lichens as Bioindicators of Heavy Metals: A Comparison Study in the Vicinity of a Copper Smelter (Poland)

This paper presents the comparison of heavy metals accumulation in spider webs from Agelenidae family (Eratigena atrica and Agelena labyrinthica) and lichens Hypogymnia physodes, exposed to pollution for two months. Webs were obtained from the laboratory-reared spiders and stretched on Petri dish while lichens were transplanted from Stobrawa Landscape Park into the study area. Concentrations of Cu, Zn, Ni, Pb and As were determined in both biomonitors and the elevated values indicated the impact of the copper smelter and surrounding roads. Our study revealed that webs were more sensitive than lichens to emissions of pollutants, and for all of the studied elements, the determined concentrations were much higher for spider webs. The results of similarity tests showed a clear difference among the concentrations of Cu, Zn, Ni and As in lichens and spider webs, with the exception of Pb, suggesting that this element could be accumulated in a similar way by both bioindicators. These differences are probably due to their morphological and ecological dissimilarities suggesting that spider webs should be favorably applied where the use of lichens is improper due to the drought, which is an unfavorable condition for accumulation of elements in lichens, or their limited uptake of elements.

Assessment of Air Quality in the South-Western Part of the Świętokrzyskie Mountains Based on Selected Indicators

This article presents the results of research on the air quality which was under the anthropogenic impact of the cement and lime industry in the Świętokrzyskie Mountains for many years. Research using geo- and bio-indicators was carried out at fixed measuring points in the years 2016–2018. Hypogymnia physodes (L.) Nyl. and two-year old Scots pine needles Pinus sylvestris L. were used for bioindication research. Physico-chemical properties of precipitation were developed on the basis of research conducted at the Jan Kochanowski University’s field research station located on the Malik Mt. Increased pH and specific electrolytic conductivity (EC) of precipitation, as well as variable concentrations of heavy metals throughout a year were found. Analysis of the chemical properties of transplanted lichens and pine needles confirmed the presence of elements from the cement and lime industry sector located in the Białe Zagłębie. Scanning electron microscope (SEM) image of the needles’ surface revealed morphologic changes resulting from pollution of stoma opening and closing by small solid particles of anthropogenic origins, disturbing gas exchange.

A database of high-resolution MS/MS spectra for lichen metabolites

While analytical techniques in natural products research massively shifted to liquid chromatography-mass spectrometry, lichen chemistry remains reliant on limited analytical methods, Thin Layer Chromatography being the gold standard. To meet the modern standards of metabolomics within lichenochemistry, we announce the publication of an open access MS/MS library with 250 metabolites, coined LDB for Lichen DataBase, providing a comprehensive coverage of lichen chemodiversity. These were donated by the Berlin Garden and Botanical Museum from the collection of Siegfried Huneck to be analyzed by LC-MS/MS. Spectra at individual collision energies were submitted to MetaboLights (https://www.ebi.ac.uk/metabolights/MTBLS999) while merged spectra were uploaded to the GNPS platform (CCMSLIB00004751209 to CCMSLIB00004751517). Technical validation was achieved by dereplicating three lichen extracts using a Molecular Networking approach, revealing the detection of eleven unique molecules that would have been missed without LDB implementation to the GNPS. From a chemist's viewpoint, this database should help streamlining the isolation of formerly unreported metabolites. From a taxonomist perspective, the LDB offers a versatile tool for the chemical profiling of newly reported species.

Response of secondary metabolites to Cu in the Cu-hyperaccumulator lichen Stereocaulon japonicum

Lichen secondary metabolites are known to be associated with heavy metal uptake and tolerance in lichens. Understanding the relationship between their secondary metabolites and heavy metals in them is important for clarifying the mechanisms of their heavy metal accumulation and tolerance. To determine the relationships between the concentrations of secondary metabolites and Cu in the Cu-hyperaccumulator lichen Stereocaulon japonicum and to clarify its response to Cu, we collected Cu-contaminated and uncontaminated samples of the lichen and determined relative concentrations of secondary metabolites and concentrations of Cu, K, glucose, and sugar alcohols in them. We found significant negative correlations between the relative concentrations of secondary metabolites-atranorin and stictic acid-and the concentration of Cu. These negative correlations can be interpreted in one of two ways: (a) S. japonicum itself reduced the relative concentrations of secondary metabolites in response to the increase of Cu concentration or (b) its carbon and energy metabolism was damaged by Cu stress, resulting in the reduction of the relative concentrations of secondary metabolites. The analysis of K, glucose, and sugar alcohols showed no effect of Cu on these concentrations, which means that the carbon and energy metabolism was not damaged by Cu stress. Therefore, the negative correlations can be interpreted that S. japonicum itself reduced the relative concentrations of secondary metabolites with the increase of Cu concentration. These findings provide a deeper understanding of the response of secondary metabolites to Cu in the lichen.

The coupled study of metal concentrations and electron paramagnetic resonance (EPR) of lichens (Hypogymnia physodes) from the Świętokrzyski National Park-environmental implications

SO₂, NO_x, and metals (including Cd, Cu, Pb, Zn, Mn, Mg, Fe) present in airborne particulate matter are a major threat to preserving good air quality. The complicated pathways and transformation processes that can change their physical/chemical state in the atmosphere renders identifying their origin extremely difficult. With the objective of alleviating this difficulty, we identified and characterized potential local and regional sources of atmospheric pollutants using bioindicators (Hypogymnia physodes) from the Świętokrzyski National Park (SE Poland): 20 lichen samples were collected during winter (February; heating period) and summer (June; vegetative period) seasons and analyzed for metal contents and free radicals concentrations. Our results indicate that the highest gaseous pollutant levels were observed during the heating season, along roads (NO₂) and at the highest elevation (SO₂). The semiquinone/phenoxyl radical concentrations correlated during the heating season with the atmospheric SO₂: ln (free radicals concentrations) = 0.025 SO_2atmosphere + 39.11. For Mn/Fe ≥ 2, the electron paramagnetic resonance (EPR) spectra presented a hyperfine splitting. Results showed that since 1994 metal concentrations increased for Cd, Mn, and Mg, Fe remained somewhat constant for Zn and Cu but slightly decreased for Pb, in agreement with the phasing out of lead in gasoline. Finally, a principal component analysis (PCA) identified two main factors controlling variability within the analyzed parameters: air pollutants transport over long distances and local fuel combustion by both transport and home heating.

Secondary metabolism in the lichen symbiosis

Lichens, which are defined by a core symbiosis between a mycobiont (fungal partner) and a photobiont (photoautotrophic partner), are in fact complex assemblages of microorganisms that constitute a largely untapped source of bioactive secondary metabolites. Historically, compounds isolated from lichens have predominantly been those produced by the dominant fungal partner, and these continue to be of great interest for their unique chemistry and biotechnological potential. In recent years it has become apparent that many photobionts and lichen-associated bacteria also produce a range of potentially valuable molecules. There is evidence to suggest that the unique nature of the symbiosis has played a substantial role in shaping many aspects of lichen chemistry, for example driving bacteria to produce metabolites that do not bring them direct benefit but are useful to the lichen as a whole. This is most evident in studies of cyanobacterial photobionts, which produce compounds that differ from free living cyanobacteria and are unique to symbiotic organisms. The roles that these and other lichen-derived molecules may play in communication and maintaining the symbiosis are poorly understood at present. Nonetheless, advances in genomics, mass spectrometry and other analytical technologies are continuing to illuminate the wealth of biological and chemical diversity present within the lichen holobiome. Implementation of novel biodiscovery strategies such as metagenomic screening, coupled with synthetic biology approaches to reconstitute, re-engineer and heterologously express lichen-derived biosynthetic gene clusters in a cultivable host, offer a promising means for tapping into this hitherto inaccessible wealth of natural products.

New erythritol derivatives from the fertile form of Roccella montagnei

Chemical investigation of the methanol extract of the fertile form of Roccella montagnei collected in Vietnam afforded twelve secondary metabolites, including five new montagnetol derivatives, orsellinylmontagnetols A-D and a furanyl derivative together with seven known compounds. Their chemical structures were elucidated by analysis of 1D and 2D NMR and high resolution mass spectroscopic data. The relative stereochemistry of two chiral centers (C-2 and C-3) of orsellinylmontagnetols A and B was elucidated by comparison of their coupling constants and the specific rotation with those reported in the literature while the absolute stereochemistry was determined by the application of a modified Mosher method for the hydroxy group at C-3. The absolute configuration (2R,3S) of the butanetetraol moiety of these compounds is in accordance with that of erythrin, a recognized chemotaxonomic marker of the genus Roccella. Five of these compounds were evaluated for their cytotoxic activities against four cancer cell lines. Only orsellinylmontagnetol A exerted a moderate activity against MCF-7 cell line with an IC₅₀ value of 68.39 ± 3.46 μM.

Infraspecific variability in baseline element composition of the epiphytic lichen Pseudevernia furfuracea in remote areas: implications for biomonitoring of air pollution

The epiphytic lichen Pseudevernia furfuracea is widely used as biomonitor of airborne trace elements and other contaminants and consists of two taxonomic varieties (var. furfuracea and var. ceratea). Here, we assessed the occurrence of inter-varietal differences in the elemental composition of paired samples of var. furfuracea and var. ceratea collected in 20 remote sites of Italian mountains. The concentration of 40 elements was measured by inductively coupled plasma mass spectroscopy, after digestion with HNO₃ and aqua regia. The magnitude of inter-varietal differences compared to the effect of large-scale site-dependent environmental factors (i.e., lithological substrate, host tree species, and altitude) on overall element content was explored by multivariate analysis techniques and tested by generalized linear mixed modeling (GLMM). Further GLMMs were separately fitted for each element testing taxonomic-related variability against uncertainty associated to the analytical procedure. Inter-varietal differences were statistically significant only for Hg and P, with higher content in var. ceratea at most sites, and for Mg and Zn, showing the opposite pattern. Since the elemental composition of P. furfuracea in remote sites was mostly affected by local lithology and climatic conditions, our results confirm that lichen material for active biomonitoring should be collected in a single ecologically homogeneous remote area. We also indicate sites in the Eastern Alps where P. furfuracea showed the minimum content of most elements, which are suggested as locations to collect lichen material for transplants. Besides the context-dependency at large spatial scale, variations of elemental composition apparently related to taxonomy, could possibly be due to unequal incidence of morphological traits of the collected material. Further research is needed to clarify this issue, and how it affects bioaccumulation phenomena.

Moss and lichen biomonitoring of atmospheric mercury: A review

Long-range transport and residence time of elemental Hg (Hg°) in air promote global dispersion and deposition in remote ecosystems. Many biotic and abiotic factors contribute to the photoreduction and phytovolatilization of Hg from terrestrial ecosystems, and the assessment of deposition and volatilization fluxes is very challenging. Mosses and lichens are widespread in nature and constitute the dominant vegetation in alpine and polar ecosystems. This review surveys the results of Hg biomonitoring with cryptogams in areas with different Hg sources and deposition processes. Lichen and moss ecophysiology, and factors affecting Hg uptake and bioaccumulation are discussed. Although some laboratory experiments indicate a linear accumulation of Hg in cryptogams exposed to Hg°, without any significant release, in nature the Hg accumulated in cryptogams is in a dynamic equilibrium with Hg in air and decreases when organisms are transplanted to clean environments. Mercury concentrations in mosses and lichens have often been used to estimate concentrations and deposition fluxes of atmospheric Hg; however, Hg° exchanges between cryptogams and air, and the time necessary for mosses and lichens to equilibrate elemental composition with changing atmospheric chemistry, preclude reliable estimates. Biological processes of Hg uptake and exchange with air cannot be reproduced by mechanical collectors, and comparisons between Hg concentrations in biomonitors and those in atmospheric deposition are scarcely reliable. However, the Hg biomonitoring with mosses and lichens is easy and cheap and allows to locate "hot spots" of natural or anthropogenic emissions and to assess spatio-temporal changes in Hg deposition patterns. Climate change is affecting the global Hg cycle through the melting of sea-ice in coastal Polar Regions, and modifying Hg sequestration in mountain ecosystems. Despite limitations, large-scale monitoring of Hg with mosses and lichens may be used as a tool to evaluate the impact of global processes in remote ecosystems.

Evaluation of urban environment pollution based on the accumulation of macro- and trace elements in epiphytic lichens

Nitrogen, phosphorus, potassium, magnesium, zinc, nickel, copper, manganese, iron and lead accumulation properties of three epiphytic lichen species (Hypogymnia physodes (L.) Nyl., Parmelia sulcata Taylor and Xanthoria parietina (L.) Th. Fr.) were compared. An assessment of pollution of the municipal environment in Słupsk (Poland) according to macro- and trace elements was also done. Lichen samples were taken in Autumn 2013 from Betula pendula, Fraxinus excelsior, Acer platanoides, A. pseudoplatanus and Populus sp. trees. Sampling stations comprised of house development areas, green urban parks, vicinity of streets with heavy traffic and industrial enterprises. It was found that lichens represent diverse accumulation properties to pollutants according to the species. X. parietina indicated the highest bioaccumulation in relation to N, K, Mg, Zn and Fe, the thalli of H. physodes accumulated the largest amounts of Ni and Pb, while P. sulcata P and Cu. Manganese was accumulated in similar quantities by all species. Evidences acquired by the use of factor analysis proved that pollution in Słupsk municipal environment is a serious issue with three major sources domination: street dust, marine factor and residual oil combustion. The high-risk areas were detected and visualized using surface maps based on Kriging algorithm. It was seen that the highest pollution occurs in the town centre, while the smallest happened on its outskirts and in urban parks.

Secondary metabolites of the lichen Hypogymnia physodes (L.) Nyl. and their presence in spruce (Picea abies (L.) H. Karst.) bark

Lichen species typically have a characteristic profile of secondary metabolites. Dense populations of Hypogymnia physodes growing frequently as epiphytes on tree branches have harmful effects on the host, likely due to their secondary compounds, which were undetected in tree tissues until now. The aim of the present study was to re-characterise the suite of secondary metabolites of H. physodes thalli and to estimate their translocation into spruce (Picea abies) bark. Thallus and bark extracts were compared using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The compounds were identified based on their UV, MS and MS/MS spectra as well as retention factors of their TLC analysis. In addition to the previously described secondary metabolites (protocetraric, physodalic, 3-hydroxyphysodic, physodic, and 2'-O-methylphysodic acids, atranorin and chloroatranorin) of H. physodes, further three were identified in its thalli: conphysodalic, 4-O-methylphysodic and α-alectoronic acids. Fragmentation patterns from the negative ionisation of each compound were proposed, some of which were described for the first time. Among all of the detected lichen substances, a few, e.g., physodalic, 3-hydroxyphysodic, physodic acids and atranorin, were present in the bark of spruce branches that were abundantly colonised by lichen. The newly identified compounds of H. physodes thalli may belong to its constant or accessory secondary metabolites. These compounds may be useful in the chemotaxonomic classification of this species. The presence of some lichen substances in spruce bark confirmed their ability to penetrate host tissues. These data suggest that H. physodes compounds may cause long-term effects on spruces in nature.

NIR spectroscopy as a tool for discriminating between lichens exposed to air pollution

Lichens are used as biomonitors of air pollution because they are extremely sensitive to the presence of substances that alter atmospheric composition. Fifty-one thalli of two different varieties of Pseudevernia furfuracea (var. furfuracea and var. ceratea) were collected far from local sources of air pollution. Twenty-six of these thalli were then exposed to the air for one month in the industrial port of Genoa, which has high levels of environmental pollution. The possibility of using Near-infrared spectroscopy (NIRS) for generating a 'fingerprint' of lichens was investigated. Chemometric methods were successfully applied to discriminate between samples from polluted and non-polluted areas. In particular, Principal Component Analysis (PCA) was applied as a multivariate display method on the NIR spectra to visualise the data structure. This showed that the difference between samples of different varieties was not significant in comparison to the difference between samples exposed to different levels of environmental pollution. Then Linear Discriminant Analysis (LDA) was carried out to discriminate between lichens based on their exposure to pollutants. The distinction between control samples (not exposed) and samples exposed to the air in the industrial port of Genoa was evaluated. On average, 95.2% of samples were correctly classified, 93.0% of total internal prediction (5 cross-validation groups) and 100.0% of external prediction (on the test set) was achieved.

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.

Effect of Hypogymnia physodes Extracts and their Depsidones on Micronucleus Distribution in Human Lymphocytes

Three lichen depsidones, physodalic acid (1), physodic acid (2), and 3-hydroxy physodic acid (3), were isolated from Hypogymnia physodes diethyl ether extract using column chromatography, and their structures determined by comparing their UV,1H and 13C NMR spectroscopic and MS data with those given in the literature, as well as with data computed by CHEM draw ultra 11 software. The contents of 1, 2 and 3 were determined in the methanol (ME), acetone (AE), and diethyl ether (EE) extracts using reversed-phase high performance liquid chromatography with photodiode array detection. The extracts, isolated depsidones 1-3 and EE fraction F23 (consisting of 90% 2 and 3, in the ratio 5.5: 1) were evaluated for their in vitro effects on chromosome aberrations in peripheral human lymphocytes using the cytochalasin-B blocked micronucleus (CBMN) assay in doses of 1 μg/mL and 2 μg/mL of final culture solution. The frequency of MN was scored in binucleated cells, and nuclear proliferation index was calculated. It was found that 1, 2, 3, F23, and EE at 1.0 μg/mL exerted a beneficial effect on lymphocyte cells giving a significant decrease of the frequency of MN in comparison with the positive control Amifostin WR-2721. Among the tested depsidones at a concentration of 1 μg/mL, 3 exhibited the most prominent effect decreasing the frequency of MN by 30.3%, followed by 2 (28.2%) and 1 (22.0%). The extracts were less effective than the isolated depsidones.

Effects of urban air pollutants on elemental accumulation and identification of oxidative stress biomarkers in the transplanted lichen Pseudovernia furfuracea

Determining the origins of heavy metals, their accumulation, and their detoxification mechanisms constitutes a major problem in understanding environmental pollution in urban areas. The objective of this study was to detect the relative air quality in Eskisehir city center (Turkey) through the transplanted epiphytic lichen Pseudovernia furfuracea as a biomonitor of the concentrations of some heavy metals accumulated and to describe their toxic effects on lichen physiology during the study period of one year. The influence of heavy metal accumulations on macroelement levels were also examined. In addition to analysis of B, K, Ca, P, S, Al, Fe, Mg, Mn, Ni, Zn, Pb, and Cu, total soluble proteins and oxidative stress parameters through glutathione (GSH) contents and glutathione S-transferase (GST) activities were also determined. Results indicate that, although the heavy metal concentrations were found to be gradually increased from the unpolluted control zone to the city center, the concentrations of macroelements S and Ca were higher in the polluted area. However, B, K, Mg, and P elements were found to be higher in the unpolluted area than in the polluted zones. It seems that heavy metals induce oxidative stress in lichens; we found enhancement of GSH concentrations and GST activity. Most probably, the expected destruction in this organism was reduced by the intervention of antioxidant capacity. Therefore, this report confirms the fact that the epiphytic lichen P. furfuracea is a good model for biomonitoring atmospheric quality for a long-term transplantation study, and oxidative stress parameters stand out as a tool for an early environment assessment of other physiological parameters.

Physiological responses of root-less epiphytic plants to acid rain

Selected physiological responses of Tillandsia albida (Bromeliaceae) and two lichens (Hypogymnia physodes and Xanthoria parietina) exposed to simulated acid rain (AR) over 3 months were studied. Pigments were depressed in all species being affected the most in Tillandsia. Amounts of hydrogen peroxide and superoxide were elevated and soluble proteins decreased only in AR-exposed Hypogymnia. Free amino acids were slightly affected among species and only glutamate sharply decreased in AR-exposed Xanthoria. Slight increase in soluble phenols but decrease in flavonoids in almost all species suggests that the latter are not essential for tolerance to AR. Almost all phenolic acids in Tillandsia leaves decreased in response to AR and activities of selected enzymes (phenylalanine ammonia-lyase, polyphenol oxidase, ascorbate- and guaiacol-peroxidase) were enhanced by AR. In lichens, considerable increase in metabolites (physodalic acid, atranorin and parietin) in response to AR was found but amount of ergosterol was unchanged. Macronutrients (K, Ca, Mg) decreased more pronouncedly in comparison with micronutrients in all species. Xanthoria showed higher tolerance in comparison with Hypogymnia, suggesting that could be useful for long-term biomonitoring.

Reducing power and radical scavenging activity of four Parmeliaceae species

The methanol extracts of four Parmeliaceae lichens (Hypogymnia physodes, Evernia prunastri, Flavoparmelia caperata and Parmelia sulcata) were screened for antioxidant properties and total phenol content. The H. physodes extract was the most effective at reducing iron(III) and scavenging 1,1-diphenyl-2-picrylhydrazyl radicals, while the P. sulcata extract was the most effective in reducing molybdenum(VI) in an acidic medium. The E. prunastri and H. physodes extracts contained more Folin-Ciocalteu reagent reactive substances than the F. caperata and P. sulcata extracts. Significant activity of the H. physodes extract in DPPH and reducing Fe(III) assays suggest that this lichen can be considered as a potential source of antioxidants.

Lichen compounds restrain lichen feeding by bank voles (Myodes glareolus)

Some lichen compounds are known to deter feeding by invertebrate herbivores. We attempted to quantify the deterring efficiency of lichen compounds against a generalist vertebrate, the bank vole (Myodes glareolus). In two separate experiments, caged bank voles had the choice to feed on lichens with natural or reduced concentrations of secondary compounds. We rinsed air-dry intact lichens in 100% acetone to remove extracellular compounds non-destructively. In the first experiment, pairs of control and rinsed lichen thalli were hydrated and offered to the bank voles. Because the lichens desiccated fast, we ran a second experiment with pairs of ground control and compound-deficient thalli, each mixed with water to porridge. Eight and six lichen species were tested in the first and second experiment, respectively. In the first, bank voles preferred compound-deficient thalli of Cladonia stellaris and Lobaria pulmonaria, but did not discriminate between the other thallus pairs. This was likely a result of deterring levels of usnic and stictic acid in the control thalli. When lichens were served as porridge, significant preference was found for acetone-rinsed pieces of Cladonia arbuscula, C. rangiferina, Platismatia glauca, and Evernia prunastri. The increased preference was caused mainly by lower consumption of control thalli. Grinding and mixing of thallus structures prevented bank voles from selecting thallus parts with lower concentration of secondary compounds and/or strengthened their deterring capacity. We conclude that some lichen secondary compounds deter feeding by bank voles.

High acidity tolerance in lichens with fumarprotocetraric, perlatolic or thamnolic acids is correlated with low pKa1 values of these lichen substances

The depsidone fumarprotocetraric acid as well as the depsides perlatolic and thamnolic acids are lichen secondary metabolites. Their first dissociation constants (pK(a1)) in methanol were determined to be 2.7 for perlatolic acid and 2.8 for fumarprotocetraric and thamnolic acids by UV spectroscopy. Lower pK(a1) values are, so far, not known from lichen substances. Several lichens producing at least one of these compounds are known for their outstanding tolerance to acidic air pollution. This is demonstrated by evaluating published pH preferences for central European lichens. The low pK(a1) values suggest that strong dissociation of the studied lichen substances is a prerequisite for the occurrence of lichens with these compounds on very acidic substrata, as protonated lichen substances of different chemical groups, but not their conjugated bases, are known to shuttle protons into the cytoplasm and thereby apparently damage lichens.

Metal homeostasis in Hypogymnia physodes is controlled by lichen substances

The hypothesis was tested that the lichen substances produced by the epiphytic lichen Hypogymnia physodes control the intracellular uptake of divalent transition metals. Incubating lichen thalli with and without their natural content of lichen substances with metal solutions showed that the lichen substances of H. physodes selectively inhibit the uptake of Cu(2+) and Mn(2+), but not of Fe(2+) and Zn(2+). Such behavior is ecologically beneficial, as ambient concentrations of Cu(2+) and Mn(2+) in precipitation and bark are known to limit the abundance of H. physodes, whereas limiting effects of Fe(2+) or Zn(2+) have never been found. This suggests that increasing the Cu(2+) and Mn(2+) tolerance stimulated the evolution of lichen substances in H. physodes. The depsidone physodalic acid is apparently most effective at reducing Cu(2+) and Mn(2+) uptake among the seven lichen substances produced by H. physodes. Probably lichen substances play a general role in the metal homeostasis of lichens.

Lichen Substances Affect Metal Adsorption in Hypogymnia physodes

Lichen substances are known to function as chelators of cations. We tested the hypothesis that lichen substances can control the uptake of toxic metals by adsorbing metal ions at cation exchange sites on cell walls. If true, this hypothesis would help to provide a mechanistic explanation for results of a recent study showing increased production of physodalic acid by thalli of the lichen Hypogymnia physodes transplanted to sites with heavy metal pollution. We treated cellulose filters known to mimic the cation exchange abilities of lichen thalli with four lichen substances produced by H. physodes (physodic acid, physodalic acid, protocetraric acid, and atranorin). Treated filters were exposed to solutions containing seven cations (Ca(2+), Cu(2+), Fe(2+), Fe(3+), Mg(2+), Mn(2+), and Na(+)), and changes to the solution concentrations were measured. Physodalic acid was most effective at influencing metal adsorption, as it increased the adsorption of Fe(3+), but reduced the adsorption of Cu(2+), Mn(2+), and Na(+), and to a lesser extent, that of Ca(2+) and Mg(2+). Reduced Na(+) adsorption matches with the known tolerance of this species to NaCl. The results may indicate a possible general role of lichen substances in metal homeostasis and pollution tolerance.