Urocanic acid as a novel scaffold for next-gen nature-inspired sunscreens: I. electronic laser spectroscopy under isolated conditions

Urocanic acid is a naturally occurring UV-A and UV-B absorbing compound found in the skin. Its use in artificial sunscreens has been abandoned because of health risks associated with the cis isomer. Here we report laser spectroscopic studies on urocanic acid and various substituted derivatives under supersonically cooled conditions. We find that the spectroscopy and excited-state dynamics of urocanic acid are dominantly determined by the nearly degenerate 1nπ* and 1ππ* electronically excited states. These properties are only affected to a minor extent by esterification of the carboxylic acid group or NH alkylation of the N3H tautomer. Tautomerization, on the other hand, has a much more profound influence and leads-from a photoprotective point of view-to more favorable excited-state dynamics. The approach presented here paves the way to tailoring the photoactive properties of urocanic acid for specific applications amongst which their use as safe UV filters.

SPLANG-a synthetic poisson-lognormal-based abundance and network generative model for microbial interaction inference algorithms

Microbes are pervasive and their interaction with each other and the environment can impact fields as diverse as health and agriculture. While network inference and related algorithms that use abundance data from pyrosequencing can infer microbial interaction networks, the ambiguity surrounding the actual underlying networks hampers the validation of these algorithms. This study introduces a generative model to synthesize both the underlying interactive network and observable abundance data, serving as a test bed for the existing and future network inference algorithms. We tested our generative model with four typical network inference algorithms; our results suggest that none of these algorithms demonstrate adequate accuracy for inferring ecologies of non-commensalistic species, either mutualistic or competitive. We further explored the potential for predictability by combining existing algorithms with an oracle algorithm built by fusing the results of several existing algorithms. The oracle algorithm reveals promising improvements in predictability, although it falls short when applied to networks characterized by dense interspecies taxa interactions. Our work underscores the need for the continued development and validation of algorithms to unravel the intricacies of microbial interaction networks.

Volatile Organic Compound Metabolism on Early Earth

Biogenic volatile organic compounds (VOCs) constitute a significant portion of gas-phase metabolites in modern ecosystems and have unique roles in moderating atmospheric oxidative capacity, solar radiation balance, and aerosol formation. It has been theorized that VOCs may account for observed geological and evolutionary phenomena during the Archaean, but the direct contribution of biology to early non-methane VOC cycling remains unexplored. Here, we provide an assessment of all potential VOCs metabolized by the last universal common ancestor (LUCA). We identify enzyme functions linked to LUCA orthologous protein groups across eight literature sources and estimate the volatility of all associated substrates to identify ancient volatile metabolites. We hone in on volatile metabolites with confirmed modern emissions that exist in conserved metabolic pathways and produce a curated list of the most likely LUCA VOCs. We introduce volatile organic metabolites associated with early life and discuss their potential influence on early carbon cycling and atmospheric chemistry.

Temperature Dependence and the Effects of Ultraviolet Radiation on the Ultrastructure and Photosynthetic Activity of Carpospores in Sub-Antarctic Red Alga Iridaea cordata (Turner) Bory 1826

The short-term effects of UV radiation and low temperature on ultrastructure, photosynthetic activity (measured as the maximal photochemical quantum yield of photosystem II: Fv/Fm), chlorophyll-a (Chl-a) contents, and UV-absorbing compounds on the carpospores of Iridaea cordata from a sub-Antarctic population were investigated. Exposure to both photosynthetically active radiation (PAR) and PAR + UV for 4 h caused ultrastructural modifications in all treatments. Under PAR + UV at 2 °C, a disruption of the chloroplast's internal organization was observed. Plastoglobuli were often found in carpospores exposed to 2 °C. 'Electron dense particles', resembling physodes of brown algae, were detected for the first time in cells exposed to PAR and PAR + UV at 8 °C. Fv/Fm decreased following 4 h exposure at 2 °C under PAR + UV (64%) and PAR (25%). At 8 °C, Fv/Fm declined by 21% only under PAR + UV. The photosynthesis of carpospores previously treated with UV partially recovered after a 4 h exposure under dim light. UV-absorbing compounds were degraded in all radiation and temperature treatments without recovery after a 4 h dim light period. Chl-a did not change, whereas total carotenoids increased under PAR at 8 °C The study indicates that although carpospores of I. cordata exhibit photoprotective mechanisms, UV radiation strongly damages their ultrastructure and physiology, which were exacerbated under low temperatures.

UV photo-degradation of the secondary lichen substance parietin: A multi-spectroscopic analysis in astrobiology perspective

The cortical anthraquinone yellow-orange pigment parietin is a secondary lichen substance providing UV-shielding properties that is produced by several lichen species. In our work, the secondary metabolite has been extracted from air-dried thalli of Xanthoria parietina. The aims of this study were to characterize parietin absorbance through UV-VIS spectrophotometry and with IR spectroscopy and to evaluate its photodegradability under UV radiation through in situ reflectance IR spectroscopy to understand to what extent the substance may have a photoprotective role. This allows us to relate parietin photo-degradability to the lichen UV tolerance in its natural terrestrial habitat and in extreme environments relevant for astrobiology such as Mars. Extracted crystals were UV irradiated for 5.59 h under N2 flux. After the UV irradiation, we assessed relevant degradations in the 1614, 1227, 1202, 1160 and 755 cm-1 bands. However, in light of Xanthoria parietina survivability in extreme conditions such as space- and Mars-simulated ones, we highlight parietin UV photo-resistance and its relevance for astrobiology as photo-protective substance and possible bio-hint.

Study on the Properties of PLA- and PP-Based Films for Food Applications Incorporating Orange Peel Extract from Agricultural by-Products

The aim of this work was to develop active packaging based on polypropylene (PP) and polylactic acid (PLA) matrices using a high value by-product extracted from orange peel as an active compound for food packaging applications. Different films with and without orange peel extract (OPE) based on PP and PLA were obtained via cast extrusion and characterized in terms of their mechanical, thermal, optical, and sealing properties. The films obtained were transparent, but when OPE was incorporated, the transmittance spectrum decreased, causing slight coloration. Mechanical properties were affected by the incorporation of OPE, as elongation at break and tensile strength increased in the cross-direction of the PP film, although the main differences found were related to the polymer itself. In addition, sealing strength also increased via the incorporation of OPE in the PP matrix. However, thermal properties were not affected by OPE in the PP matrix but slightly decreased stability in PLA. Regarding antimicrobial activity in in vitro studies, no inhibition of the growth of Listeria innocua, Saccharomyces cerevisiae, Aspergillus niger, or Escherichia coli was observed. Finally, antioxidant activity was observed in in vitro studies with 2,2-Diphenyl-1picrylhydrazyl (DPPH) radical. The results of this study showed that the obtention of materials with OPE incorporated into the PLA and PP matrix is feasible. The new materials obtained can be used for applications of oxidation-sensitive fresh products.

Bioproduction and optimization of newly characterized melanin pigment from Streptomyces djakartensis NSS-3 with its anticancer, antimicrobial, and radioprotective properties

BACKGROUND

Melanin is a natural pigment that is considered a promising biomaterial for numerous biotechnological applications across several industries. Melanin has biomedical applications as antimicrobial, anticancer, and antioxidant properties. Additionally, in the pharmaceutical and cosmetic industries, it is used in drug delivery and as a radioprotective agent. Also, melanin has environmental uses in the fields of bioremediation and the food industry. The biosynthesis of melanin pigment is an area of interest for researchers due to its multifunctionality, high compatibility, and biodegradability. Therefore, our present work is the first attempt to characterize and optimize the productivity of melanin pigment from Streptomyces djakartensis NSS-3 concerning its radioprotection and biological properties.

RESULTS

Forty isolates of soil actinobacteria were isolated from the Wadi Allaqui Biosphere Reserve, Egypt. Only one isolate, ACT3, produced a dark brown melanin pigment extracellularly. This isolate was identified according to phenotypic properties and molecular phylogenetic analysis as Streptomyces djakartensis NSS-3 with accession number OP912881. Plackett-Burman experimental design (PBD) and response surface methodology (RSM) using a Box-Behnken design (BBD) were performed for optimum medium and culturing conditions for maximum pigment production, resulting in a 4.19-fold improvement in melanin production (118.73 mg/10 mL). The extracted melanin pigment was purified and characterized as belonging to nitrogen-free pyomelanin based on ultraviolet-visible spectrophotometry (UV-VIS), Fourier transform infrared (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and NMR studies. Purified melanin demonstrated potent scavenging activity with IC50 values of 18.03 µg/mL and revealed high potency as sunscreens (in vitro SPF = 18.5). Moreover, it showed a nontoxic effect on a normal cell line (WI38), while it had a concentration-dependent anticancer effect on HCT116, HEPG, and MCF7 cell lines with IC50 = 108.9, 43.83, and 81.99 µg/mL, respectively. Also, purified melanin had a detrimental effect on the tested MDR bacterial strains, of which PA-09 and SA-04 were clearly more susceptible to melanin compared with other strains with MICs of 6.25 and 25 µg/mL, respectively.

CONCLUSION

Our results demonstrated that the newly characterized pyomelanin from Streptomyces djakartensis NSS-3 has valuable biological properties due to its potential photoprotective, antioxidant, anticancer, antimicrobial, and lack of cytotoxic activities, which open up new prospects for using this natural melanin pigment in various biotechnological applications and avoiding chemical-based drugs.

Plant-growth promotion by halotolerant black yeast Hortaea sp. strain PMGTC8 associated with salt crystals from solar saltern of Goa, India

Plant-growth-promoting microbes are sustainable alternative to improve the soil fertility and plant-growth facilitating the nutrients uptake in normal and stressed environmental conditions. Among these, halotolerant and halophilic microorganisms with plant- growth-promoting ability are better candidates that could be exploited as bioinoculants in salinity affected agriculture soils. Considering this, the current study aimed to isolate, characterize and determine the plant-growth-promoting potential of the culturable halotolerant black yeast associated with salt crystals from the solar saltern of Goa, India. The results revealed 1.3 × 104 CFU/g of viable number of colonies on 25% NaCl Tryptone Yeast Extract (NTYE) agar after 30-45 days incubation. Among ten morphologically distinct isolates, a black pigmented strain PMGTC8 was characterized as yeast-like and appeared two celled with average size of 4.30 ± 0.14 µm under scanning electron micrograph. Based on phylogenetic analysis using internal transcribed spacer (ITS) marker, the isolate showed maximum similarity to genus Hortaea. Interestingly, Hortaea sp. strain PMGTC8 (OR527117) exhibited plant-growth-promoting characteristics and caused significantly (p < 0.01) higher germination rate (93.33%), vigor index (964.22), shoot (3.95 cm) and root length (6.38 cm), and fresh weight (0.039 g) of Oryza sativa var. Korgut. This halotolerant black yeast may play a role in nutrition of the plants growing in saline soils. Conclusively, the current findings report for the first time the plant-growth-promoting potential of Hortaea sp. strain PMGTC8 associated with salt crystals of solar saltern, Goa, India for its possible use as bio-fertilizers in saline agriculture soils.

Identification of a novel quinoline-based UV-protective pigment from a psychrotrophic Arctic bacterium

AIMS

Psychrotrophs are extremophilic microorganisms that grow optimally in low temperature having many unique bioactive molecules of biotechnological applications. In this study we characterized a pigment from an arctic bacterium with protective activity towards UV exposure.

METHODS AND RESULTS

The present research reports isolation and characterization of a psychrotrophic bacteria, RSAP2, from the soil sample of NyAlesund (78°56"N, 11°54"E), Svalbard, Norway. The strain showed closest 16S rRNA gene sequence similarity (99.9%) with Kocuria indica NIO-1021. RSAP2 is a Gram-positive, coccoid aerobe which produces a yellow pigment. The optimal parameters for pigment production while grown in LB medium were 3% (w/v) NaCl and 4 days of incubation of the culture at 20°C and pH 9 with shaking (180 rpm). The pigment was extracted in methanol and acetone (2:1) and further purified through column chromatography. It was characterized by mass spectrometry, UV-Visible, fluorescence, IR, ¹ H NMR, ¹³ C NMR spectroscopy and CHNS/O -analysis. The pigment has a molecular weight of about 258 daltons and the molecular formula was determined as C₁₅ H₁₈ N₂ O₂ and is a quinoline derivative. We show that the pigment can protect E. coli against UV-mediated mutagenesis. We further demonstrate that the pigment displays a significant antimicrobial effect and in sublethal concentrations it impairs biofilm formation ability of the model organism Staphylococcus aureus.

CONCLUSIONS

The pigment of a psychrotrophic Arctic bacterium, most likely a strain of K. indica, was purified and its chemical structure was determined. The quinoline-based pigment has the ability to protect live cells from UV induced damage.

SIGNIFICANCE AND IMPACT OF STUDY

Analysis and characterization of this newly isolated quinoline-based pigment is a potential candidate for future application in skin care products.

A Perspective on Femtosecond Pump-Probe Spectroscopy in the Development of Future Sunscreens

Given the negative impacts of overexposure to ultraviolet radiation (UVR) on humans, sunscreens have become a widely used product. Certain ingredients within sunscreens are responsible for photoprotection and these are known, collectively herein, as ultraviolet (UV) filters. Generally speaking, organic UV filters work by absorbing the potentially harmful UVR and dissipating this energy as harmless heat. This process happens on picosecond time scales and so femtosecond pump–probe spectroscopy (FPPS) is an ideal technique for tracking this energy conversion in real time. Coupling FPPS with complementary techniques, including steady-state spectroscopy and computational methods, can provide a detailed mechanistic picture of how UV filters provide photoprotection. As such, FPPS is crucial in aiding the future design of UV filters. This Perspective sheds light on the advancements made over the past two years on both approved and nature-inspired UV filters. Moreover, we suggest where FPPS can be further utilized within sunscreen applications for future considerations.

Investigation of fungal biomolecules after Low Earth Orbit exposure: a testbed for the next Moon missions

The Moon is characterized by extremely harsh conditions due to ultraviolet irradiation, wide temperature extremes, vacuum resulting from the absence of an atmosphere and high ionizing radiation. Therefore, its surface may provide a unique platform to investigate the effects of such conditions. For lunar exploration with the Lunar Gateway platform, exposure experiments in Low Earth Orbit are useful testbeds to prepare for lunar space experiments and to understand how and if potential biomarkers are influenced by extra‐terrestrial conditions. During the BIOMEX (BIOlogy and Mars EXperiment) project, dried colonies of the fungus Cryomyces antarcticus grown on Lunar Regolith Analogue (LRA) were exposed to space conditions for 16 months aboard the EXPOSE‐R2 payload outside the International Space Station. In this study, we investigated the stability/degradation of fungal biomarkers in LRA after exposure to (i) simulated space and (ii) real space conditions, using Raman spectroscopy, gas chromatography–mass spectrometry and DNA amplification. The results demonstrated that fungal biomarkers were detectable after 16 months of real space exposure. This work will contribute to the interpretation of data from future biological experiments in the Cislunar orbit with the Lunar Gateway platform and/or on the lunar surface, in preparation for the next step of human exploration.

Recent advances in the discovery of novel marine natural products and mycosporine-like amino acid UV-absorbing compounds

Abstract

Bioactive compounds from marine environments represent a rich source of bioproducts for potential use in medicine and biotechnology. To discover and identify novel marine natural products (MNPs), evaluating diverse biological activities is critical. Increased sensitivity and specificity of omics technologies, especially next-generation high-throughput sequencing combined with liquid chromatography-mass spectrometry and nuclear magnetic resonance, are speeding up the discovery of novel bioactive compounds. Mycosporine-like amino acids (MAAs) isolated from many marine microorganisms are among highly promising MNPs characterized by ultraviolet radiation (UV) absorbing capacities and are recognized as a potential source of ecologically friendly sunscreens. MAAs absorb damaging UV radiation with maximum absorption in the range of 310–360 nm, including both UVA and UVB ranges. MAAs are also characterized by other biological activities such as anti-oxidant, anti-cancer, and anti-inflammatory activities. The application of modern omics approaches promoted some recent developments in our understanding of MAAs’ functional significance and diversity. This review will summarize the various modern tools that could be applied during the identification and characterization of MNPs, including MAAs, to further their innovative applications.

Key points

• New omics technologies are speeding up the discovery of novel bio-products

• The vast diversity of bioactive capacities of marine natural products described

• Marine microorganisms as a source of environmentally friendly sunscreens

Pyomelanin produced by Streptomyces sp. ZL-24 and its protective effects against SH-SY5Y cells injury induced by hydrogen peroxide

A soluble melanin pigment produced by Streptomyces sp. ZL-24 was purified and named StrSM. The elemental analysis of StrSM showed it consists of carbon, hydrogen, and oxygen. The spectrum analysis, including ultraviolet-visible absorption spectrum, Fourier-transform infrared spectrum, and pyrolysis-gas chromatography-mass spectrometry, indicated that StrSM might be pyomelanin. High performance liquid chromatography and liquid chromatography-mass spectra analysis of intermediate metabolite showed the presence of homogentisic acid (HGA). Moreover, the enzyme 4-hydroxyphenylpyruvate dioxygenase, involved in HGA biosynthesis, showed high activity during melanin production. Subsequently, a tyrosinase gene (melC2) and hydroxyphenylpyruvate dioxygenase gene double mutant demonstrated StrSM is pyomelanin. In vitro bioactivity assay showed that StrSM had excellent protective capability against SH-SY5Y cell oxidative injury. To our knowledge, the results firstly provide comprehensive data on Streptomyces pyomelanin identification and a promising candidate compound to treat oxidative injury of neurocytes.

A stable polyamine-modified zein-based nanoformulation with high foliar affinity and lowered toxicity for sustained avermectin release

BACKGROUND

A large amount of pesticides that are not deposited on desired locations due to drift and rolling, endangering the ecological environment and human health. Therefore, it is urgent to develop environmentally friendly and foliar affinity formulations. The design and construction of pesticide nano-delivery system is considered to be an effective way to solve this problem.

RESULTS

In this research, polyamine-modified zein (AM-zein) was synthesized by incorporating ethylenediamine-terminated polyethyleneimine into zein to improve its stability as a nanocarrier, enhance electrostatic force between the carrier and pesticides and plant foliage. Avermectin (AVM)-loaded nanoparticles, containing a high positive charge, were prepared by the anti-solvent method using AM-zein as carrier. The nanoparticles can be stored for 30 days without any significant change in the particle size and stably dispersed at pH 5-9. Compared to the commercial emulsifiable concentrate (EC), nanoparticles dispersions exhibited better leaf affinity, and the retention of dispersion increased from 7.82 to 13.86 mg/cm² . Interestingly, we have discovered for the first time that the ultraviolet (UV) barrier effect of zein increases while prolonging the UV exposure time; 30.47% of the encapsulated AVM remained intact after exposure to UV for 60 min, compared to only 17.13% for the EC. Insecticidal activity of AVM nanoparticles did not improve compared to EC, but they demonstrated significantly lower toxicity against zebrafish.

CONCLUSION

This research opens up a new idea for improving the stability of zein nanoparticles, providing a novel path to deliver pesticides efficiently and eco-friendly. © 2021 Society of Chemical Industry.

Intertidal Canopy-forming Seaweeds Modulate Understory Seaweed Photoprotective Compounds

Foundation species provide physical structure that enhances the diversity and abundance of associated organisms. Canopy-forming seaweeds are known to act as foundation species on rocky shores by lowering temperature and desiccation stress. Direct solar radiation, including ultraviolet (UV) light, can also reduce photosynthetic rates in algae, cause oxidative stress and DNA damage. The reduction in UV exposure provided by an algal canopy could therefore be important for understory organisms, including the red alga Chondrus crispus on New England's (USA) rocky shores, and this relationship may be more important at higher tidal elevations with increased low-tide exposure time. In field experiments, we investigated the relationship between tidal elevation and an index of C. crispus UV exposure, the concentration of UV-absorbing pigments. Low on the shore, C. crispus grew without a canopy. Higher on the shore, in the mid-intertidal zone, C. crispus was found under the canopy-forming rockweed, Fucus distichus subsp. evanescens. At this elevation, C. crispus was shaded (>50%; >1 m above MLLW). We performed a canopy removal experiment that spanned the mid-zone where C. crispus and F. distichus subsp. evanescens co-occur and the low-zone (no canopy). Following canopy removal in the mid-zone, UV pigment concentrations increased with tidal elevation. After accounting for the effect of elevation, removal of the algal canopy resulted in UV-protective pigment concentrations 2-fold higher than in un-manipulated control plots. These results suggest that amelioration of solar UV exposure might be another mechanism by which canopy seaweeds, acting as foundation species, facilitate understory seaweeds on rocky shores.

Response of Endolithic Chroococcidiopsis Strains From the Polyextreme Atacama Desert to Light Radiation

Cyanobacteria exposed to high solar radiation make use of a series of defense mechanisms, including avoidance, antioxidant systems, and the production of photoprotective compounds such as scytonemin. Two cyanobacterial strains of the genus Chroococcidiopsis from the Atacama Desert - which has one of the highest solar radiation levels on Earth- were examined to determine their capacity to protect themselves from direct photosynthetically active (PAR) and ultraviolet radiation (UVR): the UAM813 strain, originally isolated from a cryptoendolithic microhabitat within halite (NaCl), and UAM816 strain originally isolated from a chasmoendolithic microhabitat within calcite (CaCO3). The oxidative stress induced by exposure to PAR or UVR + PAR was determined to observe their short-term response, as were the long-term scytonemin production, changes in metabolic activity and ultrastructural damage induced. Both strains showed oxidative stress to both types of light radiation. The UAM813 strain showed a lower acclimation capacity than the UAM816 strain, showing an ever-increasing accumulation of reactive oxygen species (ROS) and a smaller accumulation of scytonemin. This would appear to reflect differences in the adaptation strategies followed to meet the demands of their different microhabitats.

Low temporal dynamics of mycosporine-like amino acids in benthic cyanobacteria from an alpine lake

Cyanobacteria are one of the oldest organisms on Earth and they originated at a time when damaging ultraviolet (UV) C radiation still reached the surface. Their long evolution led to several adaptations to avoid deleterious effects caused by exposure to solar UV radiation. Synthesis of sunscreen substances, such as mycosporine-like amino acids (MAAs), allows them to photosynthesise with reduced risk of cell damage. The interplay of solar UV radiation and MAAs is well documented for cyanobacteria in the plankton realm, but little is known for those in the benthic realm, particularly of clear alpine lakes.Here, we assessed the temporal dynamics of MAAs in the benthic algal community of one clear alpine lake dominated by cyanobacteria during the ice-free season and along a depth gradient using state-of-the-art analytical methods (high-performance liquid chromatography, nuclear magnetic resonance, liquid chromatography-mass spectrometry). We differentiated between the epilithic cyanobacterial community and the overlying loosely attached filamentous cyanobacteria, as we expected they will have an important shielding/shading effect on the former. We hypothesised that in contrast to the case of phytoplankton, benthic cyanobacteria will show less pronounced temporal changes in MAAs concentration in response to changes in solar UV exposure.Three UV-absorbing substances were present in both types of communities, whereby all were unknown. The chemical structure of the dominant unknown substance (maximum absorption at 334 nm) resulted in the identification of a novel MAA that we named aplysiapalythine-D for its similarity to the previously described aplysiapalythine-C.Chlorophyll-a-specific MAA concentrations for epilithic and filamentous cyanobacteria showed a significant decrease with depth, although only traces were found in the former community. The temporal dynamics in MAA concentrations of filamentous cyanobacteria showed no significant variations during the ice-free season.Our result on the low temporal MAA dynamics agrees with the reduced growth rates of benthic cyanobacteria reported for cold ecosystems. The permanent presence of this community, which is adapted to the high UV levels characteristic of clear alpine lakes, probably represents the most important primary producers of these ecosystems.

Phytochemical screening and determination of phenolics and flavonoids in Dillenia pentagyna using UV-vis and FTIR spectroscopy

Here, we report an ultrasonic-assisted extraction (UAE) of phytochemicals from bark, leaves, sepals, fruits, and seeds of Dillenia pentagyna (Roxb) using different organic solvents such as chloroform, ethanol, and n-hexane. The preliminary phytochemical screening results showed that the ethanolic extract is enriched with phenolics, flavonoids, tannin, saponin, alkaloid, and terpenoids. The profiling of phytochemicals is carried out employing UV-Vis and Fourier-transform infrared (FTIR) spectroscopy analyses. The higher amount of phenolic compounds obtained in the ethanolic extract of bark and leaves as compared to other parts of the plant. Consequently, a higher amount of total flavonoid compounds unveiled in the bark of targeted species. The ethanolic extract of bark and leaves showed good free radical scavenging activity using DPPH with inhibition percentage of 90.58 ± 1.89% and 76.46 ± 1.58%, respectively, in comparison to standard ascorbic acid at 10 μg/mL. Moreover, the half-maximal inhibitory concentration (IC₅₀) value of bark and leaves are 5.64 and 6.54 μg/mL, respectively, in comparison to standard ascorbic acid. With the best of our knowledge, it is the first report pertaining to characterization and quantification of phenols and flavonoids as well as the investigation of the medicinal property in D. pentagyna.

In vivo SPF from multifunctional sunscreen systems developed with natural compounds-A review

BACKGROUND

The use of sunscreens is mandatory, especially in countries with high ultraviolet (UV) incidence. In consequence, there has been a growing interest in using compounds from natural sources to develop new multifunctional products that protect human skin from the consequences of UV exposition. Even though there are in vitro methods to determine anti-UV efficacy, it is still required to test photoprotection activity on human skin to validate product performance.

AIM AND METHODS

In this review, we summarized all reported clinical studies about sun protection factor (SPF) measurements of sunscreens with natural compounds. We also discussed the probable action mechanism of those actives.

RESULTS

Herein, we provided an overview on recent studies concerning photoprotection activity of compounds from natural sources, for example, rutin, ferulic acid, caffeine, shea butter, and plant extracts, mainly presented in sunscreen systems with efficacy clinically established by SPF.

CONCLUSION

Our review suggested that even when the in vivo SPF evaluation has inherent difficulties, it is essential to assure the real efficacy of sunscreens. Furthermore, the incorporation of natural compounds could enhance the in vivo SPF values of such sunscreens by different mechanisms. Finally, some compounds derived from natural resources with skin benefits could be used as "green"/natural UV filters that provide broad-spectrum sunscreens with further upgrading of the multifunctional dermocosmetic formulation to enhance aesthetics and even skin health.

Marine-Derived Compounds with Potential Use as Cosmeceuticals and Nutricosmetics

The cosmetic industry is among the fastest growing industries in the last decade. As the beauty concepts have been revolutionized, many terms have been coined to accompany the innovation of this industry, since the beauty products are not just confined to those that are applied to protect and enhance the appearance of the human body. Consequently, the terms such as cosmeceuticals and nutricosmetics have emerged to give a notion of the health benefits of the products that create the beauty from inside to outside. In the past years, natural products-based cosmeceuticals have gained a huge amount of attention not only from researchers but also from the public due to the general belief that they are harmless. Notably, in recent years, the demand for cosmeceuticals from the marine resources has been exponentially on the rise due to their unique chemical and biological properties that are not found in terrestrial resources. Therefore, the present review addresses the importance of marine-derived compounds, stressing new chemical entities with cosmeceutical potential from the marine natural resources and their mechanisms of action by which these compounds exert on the body functions as well as their related health benefits. Marine environments are the most important reservoir of biodiversity that provide biologically active substances whose potential is still to be discovered for application as pharmaceuticals, nutraceuticals, and cosmeceuticals. Marine organisms are not only an important renewable source of valuable bulk compounds used in cosmetic industry such as agar and carrageenan, which are used as gelling and thickening agents to increase the viscosity of cosmetic formulations, but also of small molecules such as ectoine (to promote skin hydration), trichodin A (to prevent product alteration caused by microbial contamination), and mytiloxanthin (as a coloring agent). Marine-derived molecules can also function as active ingredients, being the main compounds that determine the function of cosmeceuticals such as anti-tyrosinase (kojic acid), antiacne (sargafuran), whitening (chrysophanol), UV protection (scytonemin, mycosporine-like amino acids (MAAs)), antioxidants, and anti-wrinkle (astaxanthin and PUFAs).

Aspergillus niger Spores Are Highly Resistant to Space Radiation

The filamentous fungus Aspergillus niger is one of the main contaminants of the International Space Station (ISS). It forms highly pigmented, airborne spores that have thick cell walls and low metabolic activity, enabling them to withstand harsh conditions and colonize spacecraft surfaces. Whether A. niger spores are resistant to space radiation, and to what extent, is not yet known. In this study, spore suspensions of a wild-type and three mutant strains (with defects in pigmentation, DNA repair, and polar growth control) were exposed to X-rays, cosmic radiation (helium- and iron-ions) and UV-C (254 nm). To assess the level of resistance and survival limits of fungal spores in a long-term interplanetary mission scenario, we tested radiation doses up to 1000 Gy and 4000 J/m². For comparison, a 360-day round-trip to Mars yields a dose of 0.66 ± 0.12 Gy. Overall, wild-type spores of A. niger were able to withstand high doses of X-ray (LD₉₀ = 360 Gy) and cosmic radiation (helium-ion LD₉₀ = 500 Gy; and iron-ion LD₉₀ = 100 Gy). Drying the spores before irradiation made them more susceptible toward X-ray radiation. Notably, A. niger spores are highly resistant to UV-C radiation (LD₉₀ = 1038 J/m²), which is significantly higher than that of other radiation-resistant microorganisms (e.g., Deinococcus radiodurans). In all strains, UV-C treated spores (1000 J/m²) were shown to have decreased biofilm formation (81% reduction in wild-type spores). This study suggests that A. niger spores might not be easily inactivated by exposure to space radiation alone and that current planetary protection guidelines should be revisited, considering the high resistance of fungal spores.

From sunscreens to medicines: Can a dissipation hypothesis explain the beneficial aspects of many plant compounds?

Medicine has utilised plant‐based treatments for millennia, but precisely how they work is unclear. One approach is to use a thermodynamic viewpoint that life arose by dissipating geothermal and/or solar potential. Hence, the ability to dissipate energy to maintain homeostasis is a fundamental principle in all life, which can be viewed as an accretion system where layers of complexity have built upon core abiotic molecules. Many of these compounds are chromophoric and are now involved in multiple pathways. Plants have further evolved a plethora of chromophoric compounds that can not only act as sunscreens and redox modifiers, but also have now become integrated into a generalised stress adaptive system. This could be an extension of the dissipative process. In animals, many of these compounds are hormetic, modulating mitochondria and calcium signalling. They can also display anti‐pathogen effects. They could therefore modulate bioenergetics across all life due to the conserved electron transport chain and proton gradient. In this review paper, we focus on well‐described medicinal compounds, such as salicylic acid and cannabidiol and suggest, at least in animals, their activity reflects their evolved function in plants in relation to stress adaptation, which itself evolved to maintain dissipative homeostasis.

Seasonal Patterns in Spectral Irradiance and Leaf UV-A Absorbance Under Forest Canopies

Plants commonly respond to UV radiation through the accumulation of flavonoids and related phenolic compounds which potentially ameliorate UV-damage to crucial internal structures. However, the seasonal dynamics of leaf flavonoids corresponding to epidermal UV absorbance is highly variable in nature, and it remains uncertain how environmental factors combine to govern flavonoid accumulation and degradation. We studied leaf UV-A absorbance of species composing the understorey plant community throughout two growing seasons under five adjacent tree canopies in southern Finland. We compared the relationship between leaf flavonol index (Iflav-repeatedly measured with an optical leaf clip Dualex) and measured spectral irradiance, understorey and canopy phenology, air temperature and snowpack variables, whole leaf flavonoid extracts, and leaf age. Strong seasonal patterns and stand-related differences were apparent in Iflav of both understorey plant communities and individual species, including divergent trends in Iflav during spring and autumn. Comparing the heterogeneity of the understorey light environment and its spectral composition in looking for potential drivers of seasonal changes in Iflav, we found that unweighted UV-A irradiance, or the effective UV dose calculated according to the biological spectral weighting function (BSWF) for plant growth (PG action spectrum), in understorey shade had a strong relationship with Iflav. Furthermore, understorey species seemed to adjust Iflav to low background diffuse irradiance rather than infrequent high direct-beam irradiance in sunflecks during summer, since leaves produced during or after canopy closure had low Iflav. In conclusion, we found the level of epidermal flavonoids in forest understorey species to be plastic, adjusting to climatic conditions, and differing according to species' leaf retention strategy and new leaf production, all of which contribute to the seasonal trends in leaf flavonoids found within forest stands.

The Evolution of Flavonoid Biosynthesis: A Bryophyte Perspective

The flavonoid pathway is one of the best characterized specialized metabolite pathways of plants. In angiosperms, the flavonoids have varied roles in assisting with tolerance to abiotic stress and are also key for signaling to pollinators and seed dispersal agents. The pathway is thought to be specific to land plants and to have arisen during the period of land colonization around 550-470 million years ago. In this review we consider current knowledge of the flavonoid pathway in the bryophytes, consisting of the liverworts, hornworts, and mosses. The pathway is less characterized for bryophytes than angiosperms, and the first genetic and molecular studies on bryophytes are finding both commonalities and significant differences in flavonoid biosynthesis and pathway regulation between angiosperms and bryophytes. This includes biosynthetic pathway branches specific to each plant group and the apparent complete absence of flavonoids from the hornworts.

Metatranscriptomic and metabolite profiling reveals vertical heterogeneity within a Zygnema green algal mat from Svalbard (High Arctic)

Within streptophyte green algae Zygnematophyceae are the sister group to the land plants that inherited several traits conferring stress protection. Zygnema sp., a mat-forming alga thriving in extreme habitats, was collected from a field site in Svalbard, where the bottom layers are protected by the top layers. The two layers were investigated by a metatranscriptomic approach and GC-MS-based metabolite profiling. In the top layer, 6569 genes were significantly upregulated and 149 were downregulated. Upregulated genes coded for components of the photosynthetic apparatus, chlorophyll synthesis, early light-inducible proteins, cell wall and carbohydrate metabolism, including starch-degrading enzymes. An increase in maltose in the top layer and degraded starch grains at the ultrastructural levels corroborated these findings. Genes involved in amino acid, redox metabolism and DNA repair were upregulated. A total of 29 differentially accumulated metabolites (out of 173 identified ones) confirmed higher metabolic turnover in the top layer. For several of these metabolites, differential accumulation matched the transcriptional changes of enzymes involved in associated pathways. In summary, the findings support the hypothesis that in a Zygnema mat the top layer shields the bottom layers from abiotic stress factors such as excessive irradiation.

P1G10, the Proteolytic Fraction from Vasconcellea cundinamarcensis, Stimulates Tissue Repair after Acute Exposure to Ultraviolet B Radiation

BACKGROUND

P1G10 is a cysteine proteolytic fraction from Vasconcellea cundinamarcensis latex, obtained by chromatographic separation on Sephadex-G10 and ultrafiltration. This fraction enhances healing in different models of skin lesions, and displays a protective/healing effect against gastric ulcers, where it was suggested an antioxidant role.

METHODS

We evaluated here the effect of topical treatment with P1G10, in mice lesions induced by UVB.

RESULTS

After single exposure to 2.4 J cm-2 UVB, P1G10 reduced erythema, increased cellularity of hypodermis, enhanced MPO activity and IL1β, and inhibited COX2 levels. These results point to an anti-inflammatory effect by P1G10. This fraction displayed antioxidant activity by reversing the depletion of glutathione (GSH), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and reducing the catalase activity increased by UVB. These changes may be related to a reduction in MDA observed in groups treated with P1G10. P1G10 also inhibited MMP-9, caspase-3 and pkat while increasing p53 levels.

Defense potential of secondary metabolites in medicinal plants under UV-B stress

Ultraviolet-B (UV-B) radiation has, for many decades now, been widely studied with respect to its consequences on plant and animal health. Though according to NASA, the ozone hole is on its way to recovery, it will still be a considerable time before UV-B levels reach pre-industrial limits. Thus, for the present, excessive UV-B reaching the Earth is a cause for concern, and UV-B related human ailments are on the rise. Plants produce various secondary metabolites as one of the defense strategies under UV-B. They provide photoprotection via their UV-B screening effects and by quenching the reactive oxygen- and nitrogen species produced under UV-B influence. These properties of plant secondary metabolites (PSMs) are being increasingly recognized and made use of in sunscreens and cosmetics, and pharma- and nutraceuticals are gradually becoming a part of the regular diet. Secondary metabolites derived from medicinal plants (alkaloids, terpenoids, and phenolics) are a source of pharmaceuticals, nutraceuticals, as well as more rigorously tested and regulated drugs. These metabolites have been implicated in providing protection not only to plants under the influence of UV-B, but also to animals/animal cell lines, when the innate defenses in the latter are not adequate under UV-B-induced damage. The present review focuses on the defense potential of secondary metabolites derived from medicinal plants in both plants and animals. In plants, the concentrations of the alkaloids, terpenes/terpenoids, and phenolics have been discussed under UV-B irradiation as well as the fate of the genes and enzymes involved in their biosynthetic pathways. Their role in providing protection to animal models subjected to UV-B has been subsequently elucidated. Finally, we discuss the possible futuristic scenarios and implications for plant, animal, and human health pertaining to the defense potential of these secondary metabolites under UV-B radiation-mediated damages.

Enhancement of the Production of Bioactive Microalgal Metabolites by Ultraviolet Radiation (UVA 365 nm)

Two marine microalgae, Nitzschia closterium and Isochrysis zhangjiangensis, treated for 9 days with photosynthetically active radiation (PAR), were subjected to 3 days of ultraviolet light band A at 365 nm (UVA365) followed by a 3 day post-UVA PAR treatment. Compared with the control that only had PAR treatment, UVA365 treatment significantly ( p < 0.05) increased the amounts of total xanthophylls in N. closterium and I. zhangjiangensis by up to 3.53- and 1.23-fold, respectively, after 3 days of UVA365 irradiation. In particular, UVA365 treatment markedly ( p < 0.05) increased two major bioactive xanthophyll pigments, fucoxanthin in N. closterium and diadinoxanthin in I. zhangjiangensis, by up to 1.97- and 1.52-fold, respectively. UVA365 treatment significantly ( p < 0.05) increased the accumulation of another bioactive microalgal metabolite, total mycosporine-like amino acids, in N. closterium and I. zhangjiangensis by up to 1.40- and 1.30-fold, respectively. UVA365 irradiation has potential as an efficient approach for enhancing the production of valuable microalgal metabolites.

Abiotic Stress Tolerance of Charophyte Green Algae: New Challenges for Omics Techniques

Charophyte green algae are a paraphyletic group of freshwater and terrestrial green algae, comprising the classes of Chlorokybophyceae, Coleochaetophyceae, Klebsormidiophyceae, Zygnematophyceae, Mesostigmatophyceae, and Charo- phyceae. Zygnematophyceae (Conjugating green algae) are considered to be closest algal relatives to land plants (Embryophyta). Therefore, they are ideal model organisms for studying stress tolerance mechanisms connected with transition to land, one of the most important events in plant evolution and the Earth's history. In Zygnematophyceae, but also in Coleochaetophyceae, Chlorokybophyceae, and Klebsormidiophyceae terrestrial members are found which are frequently exposed to naturally occurring abiotic stress scenarios like desiccation, freezing and high photosynthetic active (PAR) as well as ultraviolet (UV) irradiation. Here, we summarize current knowledge about various stress tolerance mechanisms including insight provided by pioneer transcriptomic and proteomic studies. While formation of dormant spores is a typical strategy of freshwater classes, true terrestrial groups are stress tolerant in vegetative state. Aggregation of cells, flexible cell walls, mucilage production and accumulation of osmotically active compounds are the most common desiccation tolerance strategies. In addition, high photophysiological plasticity and accumulation of UV-screening compounds are important protective mechanisms in conditions with high irradiation. Now a shift from classical chemical analysis to next-generation genome sequencing, gene reconstruction and annotation, genome-scale molecular analysis using omics technologies followed by computer-assisted analysis will give new insights in a systems biology approach. For example, changes in transcriptome and role of phytohormone signaling in Klebsormidium during desiccation were recently described. Application of these modern approaches will deeply enhance our understanding of stress reactions in an unbiased non-targeted view in an evolutionary context.

Light-controlled flavonoid biosynthesis in fruits

Light is one of the most important environmental factors affecting flavonoid biosynthesis in plants. The absolute dependency of light to the plant development has driven evolvement of sophisticated mechanisms to sense and transduce multiple aspects of the light signal. Light effects can be categorized in photoperiod (duration), intensity (quantity), direction and quality (wavelength) including UV-light. Recently, new information has been achieved on the regulation of light-controlled flavonoid biosynthesis in fruits, in which flavonoids have a major contribution on quality. This review focuses on the effects of the different light conditions on the control of flavonoid biosynthesis in fruit producing plants. An overview of the currently known mechanisms of the light-controlled flavonoid accumulation is provided. R2R3 MYB transcription factors are known to regulate by differential expression the biosynthesis of distinct flavonoids in response to specific light wavelengths. Despite recent advances, many gaps remain to be understood in the mechanisms of the transduction pathway of light-controlled flavonoid biosynthesis. A better knowledge on these regulatory mechanisms is likely to be useful for breeding programs aiming to modify fruit flavonoid pattern.

Light-controlled flavonoid biosynthesis in fruits

Light is one of the most important environmental factors affecting flavonoid biosynthesis in plants. The absolute dependency of light to the plant development has driven evolvement of sophisticated mechanisms to sense and transduce multiple aspects of the light signal. Light effects can be categorized in photoperiod (duration), intensity (quantity), direction and quality (wavelength) including UV-light. Recently, new information has been achieved on the regulation of light-controlled flavonoid biosynthesis in fruits, in which flavonoids have a major contribution on quality. This review focuses on the effects of the different light conditions on the control of flavonoid biosynthesis in fruit producing plants. An overview of the currently known mechanisms of the light-controlled flavonoid accumulation is provided. R2R3 MYB transcription factors are known to regulate by differential expression the biosynthesis of distinct flavonoids in response to specific light wavelengths. Despite recent advances, many gaps remain to be understood in the mechanisms of the transduction pathway of light-controlled flavonoid biosynthesis. A better knowledge on these regulatory mechanisms is likely to be useful for breeding programs aiming to modify fruit flavonoid pattern.

UV radiation is the primary factor driving the variation in leaf phenolics across Chinese grasslands

Due to the role leaf phenolics in defending against ultraviolet B (UVB) under previously controlled conditions, we hypothesize that ultraviolet radiation (UVR) could be a primary factor driving the variation in leaf phenolics in plants over a large geographic scale. We measured leaf total phenolics, ultraviolet-absorbing compounds (UVAC), and corresponding leaf N, P, and specific leaf area (SLA) in 151 common species. These species were from 84 sites across the Tibetan Plateau and Inner Mongolian grasslands of China with contrasting UVR (354 vs. 161 mW/cm(2) on average). Overall, leaf phenolics and UVAC were all significantly higher on the Tibetan Plateau than in the Inner Mongolian grasslands, independent of phylogenetic relationships between species. Regression analyses showed that the variation in leaf phenolics was strongly affected by climatic factors, particularly UVR, and soil attributes across all sites. Structural equation modeling (SEM) identified the primary role of UVR in determining leaf phenolic concentrations, after accounting for colinearities with altitude, climatic, and edaphic factors. In addition, phenolics correlated positively with UVAC and SLA, and negatively with leaf N and N: P. These relationships were steeper in the lower-elevation Inner Mongolian than on the Tibetan Plateau grasslands. Our data support that the variation in leaf phenolics is controlled mainly by UV radiation, implying high leaf phenolics facilitates the adaptation of plants to strong irradiation via its UV-screening and/or antioxidation functions, particularly on the Tibetan Plateau. Importantly, our results also suggest that leaf phenolics may influence on vegetation attributes and indirectly affect ecosystem processes by covarying with leaf functional traits.

Cell wall-bound ultraviolet-screening compounds explain the high ultraviolet tolerance of the Antarctic moss, Ceratodon purpureus

* Studies of ultraviolet (UV) light-induced DNA damage in three Antarctic moss species have shown Ceratodon purpureus to be the most UV tolerant, despite containing lower concentrations of methanol-soluble UV-screening compounds than the co-occurring Bryum pseudotriquetrum. * In this study, alkali extraction of cell wall-bound phenolics, combined with methanol extraction of soluble phenolics, was used to determine whether cell wall-bound UV screens explain the greater UV tolerance of C. purpureus. * The combined pool of UV screens was similar in B. pseudotriquetrum and C. purpureus, but whilst B. pseudotriquetrum had almost equal concentrations of MeOH-soluble and alkali-extractable cell wall-bound UV-screening compounds, in C. purpureus the concentration of cell wall-bound screening compounds was six times higher than the concentration of MeOH-soluble UV screens. The Antarctic endemic Schistidium antarctici possessed half the combined pool of UV screens of the other species but, as in C. purpureus, these were predominantly cell wall bound. Confocal microscopy confirmed the localization of UV screens in each species. * Greater investment in cell wall-bound UV screens offers C. purpureus a more spatially uniform, and potentially more effective, UV screen. Schistidium antarctici has the lowest UV-screening potential, indicating that this species may be disadvantaged under continuing springtime ozone depletion. Cell wall compounds have not previously been quantified in bryophytes but may be an important component of the UV defences of lower plants.

Occurrence of photoprotective compounds in yeasts from freshwater ecosystems of northwestern Patagonia (Argentina)

In this paper we present the results of research on the occurrence, induction and role of photoprotective compounds (PPCs) present in native aquatic yeasts from freshwater Patagonian ecosystems. We focus on the effect of UV radiation (UVR) as a factor that controls the level of photoprotection of yeasts, and explore its potential significance in shaping yeast distributional patterns. The research presented here combines field surveys and laboratory work, including the isolation and culture of native yeasts strains, and laboratory assays under different radiation conditions. The results obtained suggest that yeasts are common dwellers of oligotrophic Patagonian water bodies, and provide the first evidence of the distribution of PPC (carotenoid and mycosporine)-producing yeasts in temperate freshwaters. A greater proportion of carotenogenic yeasts were observed in high-elevation lakes. The yeast strains isolated from these environments were found to produce higher amounts of mycosporines (MYCs), and to present higher tolerance to UVB exposure than those from piedmont lakes. Patagonian yeasts have only one type of MYC, mycosporine-glutaminol-glucoside (myc-glu-glu), which seems common to all other yeasts. By analyzing the production of myc-glu-glu in a large number of yeasts belonging to different taxonomic groups, we propose that this compound may have potential use as a chemotaxonomic marker in yeast systematics. Collectively, our work reveals that in Patagonian freshwater yeasts there is an apparent relationship between the ability to produce PPCs, their tolerance to UV exposure and their success in colonizing habitats highly exposed to UVR.

Changes in pools of depsidones and melanins, and their function, during growth and acclimation under contrasting natural light in the lichen Lobaria pulmonaria

This study analysed relationships between secondary chemistry, lichen growth rates and external habitat factors for two groups of UV-B-absorbing secondary compounds in the lichen Lobaria pulmonaria in order to test some hypotheses on their formation and function. Medullary depsidones and cortical melanins were quantified in thalli transplanted to three successional forest stands (shaded young forest, open old forest, sun-exposed clear-cut area) and subjected to different watering regimes (spraying with water, water + nitrogen, no spraying). Growth rates were already known. The total concentration of all seven depsidones was constant across the entire range of growth rates and sun exposures, showing that these depsidones serve functions other than photoprotection. Thalli from the well-lit transplantation sites had the highest synthesis of melanins. Within each forest type there was a trade-off between growth and melanin synthesis. Melanins and photosynthetic acclimation enhanced survival on a subsequent exposure to high light intensity, despite excessive temperatures resulting from higher absorption of solar energy in melanic thalli relative to pale thalli. In conclusion, the highly responsive melanic pigments play a photoprotective role in light acclimation, whereas the constant amount of depsidones across a wide spectrum of growth ranges and irradiances is consistent with herbivore defence functions.

The effects of stress on plant cuticular waxes

Plants are subject to a wide range of abiotic stresses, and their cuticular wax layer provides a protective barrier, which consists predominantly of long-chain hydrocarbon compounds, including alkanes, primary alcohols, aldehydes, secondary alcohols, ketones, esters and other derived compounds. This article discusses current knowledge relating to the effects of stress on cuticular waxes and the ways in which the wax provides protection against the deleterious effects of light, temperature, osmotic stress, physical damage, altitude and pollution. Topics covered here include biosynthesis, morphology, composition and function of cuticular waxes in relation to the effects of stress, and some recent findings concerning the effects of stress on regulation of wax biosynthesis are described.

Is UV-B radiation affecting charophycean algae in shallow freshwater systems?

The objective of this study was to determine the effects of UV-B radiation on charophycean algae under natural conditions, since charophytes enhance water transparency in freshwater systems and levels of UV-B radiation have increased by ozone depletion. Potential and actual UV-B effects were studied by combining a glasshouse experiment in which plants were exposed to various levels of UV-B radiation and field measurements in two freshwater systems dominated by charophytes in the Netherlands. The glasshouse experiment showed that charophytes were sensitive to UV-B radiation. UV-B radiation negatively affected growth, while it increased levels of DNA damage in Chara aspera. Moreover, the charophytes did not seem to develop UV-B screens to protect against UV-B radiation since no increase in UV-B absorbing compounds was found. At field conditions, both spectroradiometrical measurements and DNA dosimeters showed that UV-B radiation was attenuated quickly in both freshwater systems, indicating that UV-B does not reach the submerged charophyte vegetation. However, specific conditions, like fluctuating water tables, may result in UV-B exposure to charophytes for certain periods annually.