Ultraviolet-absorbing Compounds Research Articles

Determination of 16 ultraviolet–absorbing compounds in marine invertebrates by using LC-USI-MS/MS coupled with QuEChERS

In this study, we examined multiple endocrine-disrupting ultraviolet-absorbing compounds (UVACs) in marine invertebrates used in personal care products and packaging. Modified QuEChERS and liquid chromatography UniSpray ionization tandem mass spectrometry were used to identify 16 UVACs in marine invertebrates. Matrix-matched calibration curves revealed high linearity (r ≥ 0.9929), with limits of detection and quantification of 0.006–1.000 and 0.020–3.000 ng/g w.w., respectively. In oysters, intraday and interday analyses revealed acceptable accuracy (93%–120%) and precision (≤18%), except for benzophenone (BP) and ethylhexyl 4-(dimethylamino) benzoate. Analysis of 100 marine invertebrate samples revealed detection frequencies of 100%, 98%, 89%, 64%, and 100% for BP, 4-hydroxybenzophenone, 4-methylbenzophenone, 4-methylbenzylidene camphor, and benzophenone-3 (BP-3), respectively. BP and BP-3 were detected at concentrations of 4.40–27.39 and < 0.020–0.560 ng/g w.w., respectively, indicating their widespread presence. Overall, our proposed method successfully detected UVACs in marine invertebrates, raising concerns regarding their potential environmental and health effects.

Risk Assessment of Exposure to Ultraviolet-Absorbing Compounds via Consumption of Packaged Juice, Milk and Marine Invertebrates

Risk Assessment of Exposure to Ultraviolet-Absorbing Compounds via Consumption of Packaged Juice, Milk and Marine Invertebrates

Influence of common palynological extraction treatments on ultraviolet absorbing compounds (UACs) in sub-fossil pollen and spores observed in FTIR spectra

IntroductionBiological life, atmospheric circulation and the Earth’s climate may be influenced by UV-B radiation. In plants, Ultraviolet Absorbing Compounds (UACs) are an indicator of UV-B exposure, and the abundance of UACs in pollen and spores of embryophytes is measurable using Fourier Transform Infrared (FTIR) micro-Spectroscopy. However, understanding the influence of common chemical pre-treatments on sub-fossil pollen and spores with a view to UV-B reconstruction still requires investigation.MethodsHere, peat samples collected from a Late Holocene raised bog were treated with different chemicals (HCl, KOH, and acetolysis) for varying treatment times (up to 210 min). Pollen or spores of three common taxa (Alnus, Calluna and Sphagnum) were isolated and FTIR spectra obtained on individual grains. The spectra were compared to modern pollen and spore samples collected nearby.ResultsSpectra of modern and sub-fossil samples show several visible differences related to lipid and protoplast contents. The results of chemical treatments on sub-fossil pollen and spores reveal that HCl produced limited changes, while KOH and acetolysis altered several peaks, including the UAC-related aromatic peak at 1516 cm−1. We observe that all treatments modify the FTIR spectra to some degree, from weakest (HCl) to strongest (acetolysis). With respect to reduction of UAC peak area and treatment time, we observe in some cases a significant log-decay relationship, notably for KOH treatment on Calluna pollen and acetolysis on Sphagnum spores. Compared to untreated control samples, UAC peak area in Alnus, Calluna and Sphagnum reduced by 68%, 69% and 60% respectively, after only 3 min of acetolysis treatment. After 60 minutes of acetolysis treatment UAC peaks were reduced by 77%, 84% and 88%.DiscussionDue to the potential for taxon-specific effects and significant reductions in UAC peak area even within short treatment times, our recommendation for future applications in palaeoecological studies on palynomorph chemistry is to avoid chemical digestions in the pollen extraction process in favour of separation methods including micro-sieving and density separation.

Monthly Variation in Mycosporine-like Amino Acids from Red Alga Dulse (Devaleraea inkyuleei, Formerly Palmaria palmata in Japan)

Mycosporine-like amino acids (MAAs) are natural ultraviolet-absorbing compounds found in microalgae and macroalgae. MAA content changes seasonally and in response to environmental factors. We previously investigated MAAs from the red alga dulse (Devaleraea inkyuleei, formerly Palmaria palmata in Japan) in Usujiri, Hokkaido, Japan, from 2019 to 2020. At that time, some factors affecting MAA content were still unclear. In this study, we investigated MAA variation during the period from January to June 2021, and evaluated new methods of MAA extraction from dulse. We recorded a maximum MAA extraction yield (7.03 µmol/g dry weight) on 25 March 2021. Over the course of our three years of investigations from 2019 to 2021, we found that dulse was most suitable for MAA preparation from the middle of February to late April. In the later work reported in this paper, we improved our extraction method by using a lower-risk organic solvent (ethanol) rather than methanol. In addition, we evaluated MAA extraction using different levels of ethanol concentration (25, 50, and 99%) and different extraction times (2, 6, and 24 h). We found that extraction with 25% ethanol for 24 h increased MAA content by a factor of 3.2, compared with our previous extraction method. In summary, we determined the most suitable sampling period for Usujiri dulse, to extract the highest content of MAAs. We also improved the effectiveness of the extraction process.

The Preparation of Anti-Ultraviolet Composite Films Based on Fish Gelatin and Sodium Alginate Incorporated with Mycosporine-like Amino Acids

Mycosporine-like amino acids (MAAs) are ultraviolet-absorbing compounds and have antioxidant functions. In this paper, MAAs were added into fish gelatin/sodium alginate films as an anti-ultraviolet additive. The effects of 0–5% MAAs (w/w, MAAs/fish gelatin) on the physical properties, antioxidant properties, antibacterial properties and anti-ultraviolet properties of fish gelatin/sodium alginate films were investigated. The results suggest that the content of the MAAs influenced the mechanical properties. The water content, swelling and water vapor permeability of the films were not altered with the addition of MAAs. In addition, the composite films showed effective antioxidant activity and antimicrobial activity. The incorporation of MAAs significantly improved the DPPH radical scavenging activity of the films from 35.77% to 46.61%. Moreover, the block ultraviolet rays’ ability was also greatly improved when the film mixed with the MAAs and when the value of the light transmission was 0.6% at 350 nm. Compared with the pure composite film, the growth of E. coli covered by the composite film with 3.75% and 5% MAAs exhibited the best survival rate. These results reveal that MAAs are a good film-forming substrate, and MAAs have good potential to prepare anti-ultraviolet active films and antioxidant active films for applications. Overall, this project provides a theoretical basis for the study of active composite films with anti-ultraviolet activities, and it provides new ideas for the application of MAAs.

In silico analysis of enzymes involved in mycosporine-like amino acids biosynthesis in Euhalothece sp.: Structural and functional characterization

Mycosporine-like amino acids (MAAs) are ultraviolet-absorbing compounds synthesized by photoautotrophic microorganisms such as cyanobacteria. They have applications as UV protectants and antioxidants in the cosmetic and pharmaceutical sectors. To date, >30 different types of MAAs have been identified, having an absorption range between 310 and 365 nm that covers most of the UVR spectrum (~295–400 nm). In the study, MAAs were extracted and partially purified from a euryhaline Euhalothece sp. Thereafter, in silico analysis of the MAAs biosynthetic genes was conducted to determine the physicochemical characteristics, structural properties, functional analysis and homology model. High salinity stress (120 g L−1) significantly enhanced the production of MAAs (~56 %) in Euhalothece sp. Bioinformatics analysis of the genome of Euhalothece sp. revealed a distinctive mys gene cluster that contained six genes (mysA to mysE), compared to four genes commonly found in MAA-producing cyanobacteria. Interestingly, both EEVS and DHQ synthase were present, indicating the potential to synthesize MAAs via both the shikimate and sedoheptulose 7-phosphate pathways. Secondary structure analysis confirmed that in all the biosynthetic enzymes, the major components were the alpha-helices with random coils. This study emphasized the unique genes for MAAs in Euhalothece sp. as well as highlighted the potential metabolite pathways for commercial production. Elucidation of the protein structure, physicochemical properties, and interactions provides scientific insight into the biosynthesis of MAAs from hypersaline cyanobacteria. Additionally, it is essential for determining the applications of these novel photoprotective compounds.

The protection of Salicornia rubra from ultraviolet radiation by betacyanins and phenolic compounds.

Salicornia rubra is a commonly occurring annual species of the salt playas of the Great Basin Desert of the western United States. In such habitats, plants experience high levels of ultraviolet radiation, which could potentially damage DNA. As a member of the Amaranthaceae (Caryophyllales), S. rubra shoots typically contain high concentrations of the red-violet pigments called betacyanins, which are ultraviolet-absorbing compounds. Nevertheless, some specimens of S. rubra are green even when growing with full exposure to the sun. We, therefore, tested several hypotheses regarding the causes of variation among S. rubra plants in betacyanin concentration and the role of betacyanins in the absorption of ultraviolet radiation. We measured ultraviolet radiation absorption and the concentrations of betacyanins and phenolic compounds of the cell sap expressed from red and green plants growing in full sun, as well as plants grown under various levels of shade. We found that while betacyanin concentrations were predictable from plant color (red plants contained more betacyanins than green plants), the ability to absorb ultraviolet radiation was determined primarily by the concentration of phenolic compounds, which was determined by the level of exposure to the sun. Therefore, the DNA of green plants growing in full sun appears to be at no greater risk than the DNA of red plants.

The dinoflagellate Akashiwo sanguinea will benefit from future climate change: The interactive effects of ocean acidification, warming and high irradiance on photophysiology and hemolytic activity

Due to global climate change, marine phytoplankton will likely experience low pH (ocean acidification), high temperatures and high irradiance in the future. Here, this work report the results of a batch culture experiment conducted to study the interactive effects of elevated CO2, increased temperature and high irradiance on the harmful dinoflagellate Akashiwo sanguinea, isolated at Dongtou Island, Eastern China Sea. The A. sanguinea cells were acclimated in high CO2 condition for about three months before testing the responses of cells to a full factorial matrix experimentation during a 7-day period. This study measured the variation in physiological parameters and hemolytic activity in 8 treatments, representing full factorial combinations of 2 levels each of exposure to CO2 (400 and 1000μatm), temperature (20 and 28°C) and irradiance (50 and 200μmol photons m−2s−1). Sustained growth of A. sanguinea occurred in all treatments, but high CO2 (HC) stimulated faster growth than low CO2 (LC). The pigments (chlorophyll a and carotenoid) decreased in all HC treatments. The quantum yield (Fv/Fm) declined slightly in all high-temperature (HT) treatments. High irradiance (HL) induced the accumulation of ultraviolet-absorbing compounds (UVabc) irrespective of temperature and CO2. The hemolytic activity in the LC treatments, however, declined when exposed to HT and HL, but HC alleviated the adverse effects of HT and HL on hemolytic activity. All HC and HL conditions and the combinations of high temperature*high light (HTHL) and high CO2*high temperature*high light (HCHTHL) positively affected the growth in comparison to the low CO2*low temperature*low light (LCLTLL) treatment. High temperature (HT), high light (HL) and a combination of HT*HL, however, negatively impacted hemolytic activity. CO2 was the main factor that affected the growth and hemolytic activity. There were no significant interactive effects of CO2*temperature*irradiance on growth, pigment, Fv/Fm or hemolytic activity, but there were effects on Pm, α, and Ek. If these results are extrapolated to the natural environment, it can be hypothesized that A. sanguinea cells will benefit from the combination of ocean acidification, warming, and high irradiance that are likely to occur under future climate change. It is assumed that faster growth and higher hemolytic activity and UVabc of this species will occur under future conditions compared with those the current CO2 (400μatm) and temperature (20°C) conditions.

Ultraviolet absorbing compounds provide a rapid response mechanism for UV protection in some reef fish

The external mucus surface of reef fish contains ultraviolet absorbing compounds (UVAC), most prominently Mycosporine-like Amino Acids (MAAs). MAAs in the external mucus of reef fish are thought to act as sunscreens by preventing the damaging effects of ultraviolet radiation (UVR), however, direct evidence for their protective role has been missing. We tested the protective function of UVAC's by exposing fish with naturally low, Pomacentrus amboinensis, and high, Thalassoma lunare, mucus absorption properties to a high dose of UVR (UVB: 13.4W∗m−2, UVA: 6.1W∗m−2) and measuring the resulting DNA damage in the form of cyclobutane pyrimidine dimers (CPDs). For both species, the amount of UV induced DNA damage sustained following the exposure to a 1h pulse of high UVR was negatively correlated with mucus absorbance, a proxy for MAA concentration. Furthermore, a rapid and significant increase in UVAC concentration was observed in P. amboinensis following UV exposure, directly after capture and after ten days in captivity. No such increase was observed in T. lunare, which maintained relatively high levels of UV absorbance at all times. P. amboinensis, in contrast to T. lunare, uses UV communication and thus must maintain UV transparent mucus to be able to display its UV patterns. The ability to rapidly alter the transparency of mucus could be an important adaptation in the trade off between protection from harmful UVR and UV communication.

Metabolic and behavioral responses of the reef fish Patagonotothen cornucola to ultraviolet radiation: Influence of the diet

Most of the studies devoted to assess the effects of ultraviolet radiation (UVR) on fishes have been done with early life stages (i.e., eggs and larvae) as they are the most vulnerable to these wavelengths; however, the effects of UVR on juveniles or adults are less clear. This study evaluated the effects of UVR and diet (i.e., rich and poor in ultraviolet-absorbing compounds; UVAC) on the metabolic rates (respiratory frequency) and behavior (prey capture time) of juveniles of the reef fish Patagonotothen cornucola, a common species inhabiting the intertidal areas of the Patagonian coast. UVR was a significant stress factor for P. cornucola by increasing its respiratory frequency, which could be related to the costs of repairing any cellular components damaged during the exposure. Fish exposed to UVR took more time to detect and capture their prey, which could lead to a reduction in the prey capture rates, with the concomitant effects on growth. In addition, juveniles feeding on rich-UVAC diet had a significant lower respiratory frequency than those feeding on poor-UVAC diet. This differential response was not evident in the prey capture time. In their natural environment, P. cornucola could feed on a varied diet and could also partially avoid the exposure to UVR by hiding under the rocks or macroalgae. Future studies should consider the broad variety of diets that could be found in rocky intertidal areas, and how their qualities (in terms of UVAC content) could help to counteract the UVR effects on juvenile fish.

Spatial variability of ultraviolet-absorbing compounds in an aquatic liverwort and their usefulness as biomarkers of current and past UV radiation: A case study in the Atlantic–Mediterranean transition

The spatial variability of ultraviolet-absorbing compounds (UVACs) in the freshwater liverwort Jungermannia exsertifolia subsp. cordifolia was studied in mid-latitudes (the Atlantic–Mediterranean transition) across a wide lati-altitudinal gradient, with the aim of testing the usefulness of UVACs as biomarkers of current ambient levels of UV radiation. We analysed 17 samples from streams located in the main mountain ranges of the Iberian Peninsula, differentiating methanol-soluble (SUVACs, mainly located in the vacuoles) and methanol-insoluble (IUVACs, bound to cell walls) compounds, since they represent different manners to cope with UV radiation. In both fractions, the bulk level of UVACs and the concentrations of several individual compounds were measured. In addition, we measured Fv/Fm, DNA damage and sclerophylly index (SI) as possible additional UV biomarkers. UVACs showed a high variability, probably due not only to the gradients of macroenvironmental factors (UV radiation, PAR, and water temperature), but also to microenvironmental factors inherent to the dynamic nature of mountain streams. Two soluble coumarins were positively correlated with UV levels and could be used for ambient UV biomonitoring in the spatial scale. In contrast to the variability in UVACs, the relatively homogeneous values of Fv/Fm and the lack of any DNA damage made these variables useless for ambient UV biomonitoring, but suggested a strong acclimation capacity of this liverwort to changing environmental conditions (in particular, to UV levels). Finally, UVACs of fresh samples of the liverwort were compared to those of herbarium samples collected in the same lati-altitudinal gradient. SUVACs were significantly higher in fresh samples, whereas IUVACs generally showed the contrary. Thus, IUVACs were more stable than SUVACs and hence more adequate for retrospective UV biomonitoring. In conclusion, UVAC compartmentation should be taken into account for bryophyte-based UV biomonitoring in future studies.

UV radiation biomonitoring using cell compartmentation of UV-absorbing compounds in herbarium samples of a liverwort

Ultraviolet-absorbing compounds (UVACs) were analyzed in 90 herbarium samples of the liverwort Jungermannia exsertifolia subsp. cordifolia collected throughout Spain in the period 1913–2006, in order to evaluate their usefulness in UV radiation biomonitoring. This was assessed, for the first time in bryophytes, differentiating the soluble (mainly vacuolar) and insoluble (cell wall-bound) UVACs (respectively, SUVACs and IUVACs), which may represent different mechanisms to cope with UV radiation. The bulk levels of SUVACs and IUVACs, and the concentrations of seven individual compounds (five SUVACs and two IUVACs) were analyzed, and several environmental variables of the sampling points were obtained: longitude, latitude, altitude, ozone column, and modelled UV levels.Diverse positive relationships of UVAC variables with UV radiation levels were identified in both the temporal and spatial scales. The soluble compound p-coumaroylmalic acid showed significantly higher concentrations in the years after the onset of stratospheric ozone degradation (around 1975) with respect to the previous years. The bulk level and the concentrations of three individual SUVACs were higher in the Spanish samples analyzed in the present study than in the northern European samples analyzed in a previous study in which IUVACs were not considered. The bulk level of IUVACs was the biological variable best spatially correlated with the UV exposure of the samples and with important factors determining it, such as altitude and latitude. Furthermore, the bulk level of IUVACs was the biological variable selected by a stepwise multiple linear regression analysis to reconstruct the past levels of UV-B radiation. The reconstructed UV-B did not show a clear trend in the period 1913–2006, which was coincident with other climatic and biological UV reconstructions. Both SUVACs and IUVACs were significant loading factors differentiating summer and autumn samples in the Principal Components Analysis conducted using both UVACs and the environmental variables, but again the bulk level of IUVACs was the main loading factor differentiating the samples collected from the highest and most UV-exposed localities (Sierra Nevada). In general, these findings suggest that UVACs were stimulated by increased UV levels in time or space, and that IUVACs would be better UV protectants than SUVACs, probably due to their more efficient screening capacity.Overall, UVACs of J. exsertifolia subsp. cordifolia were good UV biomarkers, and their location in the soluble or cell wall-bound fractions determined their usefulness in the different aspects of UV biomonitoring, including the assessment of the UV-B increase associated to anthropogenic ozone degradation.

The migration and transformation of dissolved organic matter during the freezing processes of water

This study investigated the partitioning behavior of dissolved organic matter (DOM) in liquid and ice phases, as well as the changes in the optical properties and chlorine reactivity of DOM during the freezing processes of water. DOM was rejected from the ice phase and accumulated in the remaining liquid phase during water freezing. Moreover, the decrease in freezing temperature, as well as the increase in dissolved organic carbon (DOC) concentration of feed water, caused an increase in DOM captured in the ice phase. The ultraviolet-absorbing compounds, trihalomethane precursors, as well as fulvic acid- and humic acid-like fluorescent materials, were more liable to be to be rejected from the ice phase and were more easily retained in the unfrozen liquid phase during water freezing, as compared with organics (on average) that comprise DOC. In addition, it was also found a higher accumulation of these organics in the unfrozen liquid phase during water freezing at higher temperature. The freeze/thaw processes altered the quantity, optical properties, and chlorine reactivity of DOM. The decrease in ultraviolet light at 254nm as well as the production of aromatic protein- and soluble microbial byproduct-like fluorescent materials in DOM due to freeze/thaw were consistently observed. On the other hand, the changes in DOC, trihalomethane formation potential, and fulvic acid- and humic acid-like fluorescence caused by freeze/thaw varied significantly between samples.

Ultraviolet-absorbing compounds from the cell walls of an aquatic liverwort are more efficiently extracted by alkaline than by enzymatic digestion

The accumulation of ultraviolet-absorbing compounds (UVACs) within the cell walls of bryophytes provides a spatially uniform filter of ultraviolet-B (UV-B) radiation, and thus represents an important protective mechanism against its adverse effects. Here, the abilities of several cell-wall-degrading enzymes and of alkali (NaOH) in extracting cell-wall-bound UVACs from the aquatic liverwort Jungermannia exsertifolia Steph. subsp. cordifolia (Dumort.) Váňa were compared, in order to select the most appropriate extraction method and to achieve the most reliable assessment of the degree of protection afforded by UVACs against UV-B. We analysed both the overall level of UVACs and the concentrations of two hydroxycinnamic acids (p-coumaric acid and ferulic acid). The most effective extraction (statistically significant) of cell-wall-bound UVACs, in terms both of their overall levels and of the concentrations of individual compounds, was achieved using alkaline digestion, which was more efficient than any of the enzymatic digestions trialled. This may be attributable to the ability of the alkali to break simultaneously both hydrogen bonds and covalent bonds within the cell wall, including ester linkages between phenolics and carbohydrates. In addition, alkaline digestion was more rapid than enzymatic digestions, and was not excessively aggressive, because the molecular integrity of the individual compounds analysed was preserved. Thus, alkaline digestion can be recommended for the extraction of cell-wall-bound UVACs in J. exsertifolia subsp. cordifolia, whether these compounds are to be evaluated overall or individually.

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/cm2 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.

C-6.混合蛍光体による紫外吸収物質の定性分析

C-6.混合蛍光体による紫外吸収物質の定性分析

Comparison of susceptibility of leaves on short-term UV-B irradiation

Abstract The effects of short-time ultraviolet-B irradiation (0.74 kJ m-2 d-1) at light on cucumber and peppermint leaves were studied.Aconsiderable decrease of the most important chlorophyll fluorescence parameters values mainly in the cucumber leaves, compared to the control, was observed. It indicates damages as well as at a donor and acceptor side of photosystem II, specially in the oxygen evolving complex, electron transport and connected with the dark reactions. In the peppermint leaves these values were unchanged or slight decreased. After 24 h from disappearing of the applied UV-B stress, adverse changes became established, especially in the cucumber leaves show irreversible damages of photosystem II. Coefficient of nonphotochemical quenching increased by 50% in the peppermint leaves, while in cucumber remained unchanged. Chlorophyll delayed luminescence coefficient was decreased by 36% in the UV-B irradiated cucumber leaves and by 25% in the peppermint leaves. Content of ultraviolet-absorbing compounds was higher in peppermint leaves by 78% than in the cucumber. Generally, peppermint seemed to be more tolerant to the applied UV-B radiation compared to cucumber.

Effects of enhanced UV-B radiation on hydroxycinnamic acid derivatives extracted from different cell compartments in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia

We examined the responses of ultraviolet-absorbing compounds (UVAC) to enhanced UV-B radiation in the aquatic liverwort Jungermannia exsertifolia subsp. cordifolia for 31 days under laboratory conditions. Samples were exposed to three radiation regimes: P (only photosynthetic radiation), PA (photosynthetic + UV-A radiation) and PAB (photosynthetic + UV-A + UV-B radiation). We measured both the bulk UV absorbance of the methanolic extracts and the levels of individual UVAC. In both cases, the methanol-soluble and the methanol-insoluble, alkali-extractable cell wall-bound fractions were analyzed. The bulk UV absorbance of the soluble fraction was higher than that of the cell wall-bound fraction. The bulk UV absorbances of both fractions increased under enhanced UV-B (PAB regime). Five different hydroxycinnamic acid (HCA) derivatives were found in the soluble fraction and two additional ones in the cell wall-bound fraction, among which only p-coumaroylmalic acid in the soluble fraction and p-coumaric acid in the cell wall-bound fraction increased under enhanced UV-B. The maximum quantum yield of PSII (F(v) /F(m)) decreased and DNA damage (amount of thymine dimers) strongly increased under enhanced UV-B, showing UV-B-induced damage. We conclude that methanol-soluble and cell wall-bound fractions of the liverwort studied have different UVAC, and each individual compound may respond in a different way to UV-B radiation. Thus, the analysis of individual UVAC in both the methanol-soluble and cell wall-bound fractions is advisable to better evaluate the protection mechanisms of liverworts against UV-B radiation. In particular, p-coumaric acid and p-coumaroylmalic acid seem to be especially UV-B responsive and merit further investigation.

Ultraviolet-absorbing compounds in milk are related to forage polyphenols

The aim of this work was to characterize UV-absorbing compounds (UAC) in milk in relation to diet. In winter, 4 groups of cows each received a different diet: concentrate rich containing 35% cocksfoot hay (CCH), maize silage (MS), rye grass silage (RS), or rye grass hay (RH). In summer, 2 additional diets were given: mountain grassland hay (GH) and mountain grassland pasture (GP). Polyphenols were analyzed by HPLC and Folin reaction on forages and UAC were extracted from milks and analyzed by HPLC. In forages, the number of polyphenols was lowest in MS (57) and greatest in GP (85). Twenty-four peaks were identified, accounting for 28 to 47% peak area at 280nm. Caffeoyl compounds and flavonoid glycosides were mainly found in RH, GH, and GP. Hydrolyzed compounds such as hydroxycinnamic acids and aglycones were found in MS and RS. Estimated amounts of polyphenols were lowest for MS (3.7 g/kg), roughly similar for CH, RS, and RH (about 15 g/kg), and greatest for GH and GP (21.6 and 35.3 g/kg, respectively). About 230 different peaks were separated in milks. Milks from RH and GP contained the lowest (87) and the greatest (127) numbers of peaks, respectively. Only 10 peaks were identified, accounting for 21 to 54% of the total spectra area. In addition to the major compound hippuric acid, phenylacetic acid, benzoic acid, 4-hydroxybenzoic acid benzaldehyde, catechol, and small amounts of ferulic acid were found in varying amounts depending on the diet. Flavonoids such as quercetin, luteolin, and apigenin were also present. Hippuric acid was clearly related to the presence of caffeoylquinic compounds in forages. Other identified UAC may originate essentially from forage simple polyphenols or from cell wall aromatics. Some of the several unknown compounds may also originate from the transformation of other nutrients. Estimated amounts of UAC were widely variable within each animal group. They were surprisingly high in CCH and roughly similar in all milks from preserved forages (about 3.6 mg/L), with generally greater values for GH milks, whereas the greatest amount was found in GP milks (13.3 mg/L). Hierarchical clustering clearly discriminated the 6 diets, showing that there were major differences in GP milks. Some UAC were specific to one or a group of diets. Ultraviolet-absorbing compounds are therefore a potential tool to distinguish between milks according to diet. In addition, they may have a bioactive effect on milk component conservation or on human health.

In situ measurement of spectral changes in the anterior eye following application of ultraviolet-absorbing compounds

The ocular structures are very sensitive to damage from ultraviolet (UV) radiation, exposure is linked to corneal and conjunctival damage, cataract formation and may also be implicated in the aetiology of age-related macular degeneration. These structures are usually protected by wearing suitable eyeglasses and goggles. An alternative to conventional eyeglasses/goggles is the concept of “liquid sunglasses” which involve the topical application of eye drops that are designed to block harmful UV radiation reaching the sensitive ocular surfaces. The evaluation of such compounds directly applied to the eye surface requires in situ measurements to compare the efficacy of different formulations. A novel ocular spectrometer system has been used to evaluate changes in the transmission of ultraviolet (UV) radiation through the anterior eye following topical application of candidate UV-absorbing formulations. The key feature of the system is the ability to propagate a beam of light tangentially through the anterior eye using a compact, hand-held lens assembly incorporating UV-transmitting optical fibres. A range of formulations containing UV-absorbing compounds were topically applied to ex vivo rabbit eyes. Significant increases in the absorption of the UV spectrum were detected in seven of the eight formulations studied, demonstrating the potential of this measurement technique in the evaluation of formulations developed as potential topical ocular sunscreens.