UVA Absorbance Research Articles

Antioxidant, photoprotective, cytotoxic, and antimicrobial activities of Albuca amoena Batt.

Introduction: Albuca amoena Batt. is an endemic plant from Morocco used for treating melanoma or leishmaniasis. The aim of this study is to test the antioxidant, photoprotective, cytotoxic, and antimicrobial properties of this plant. Methods: The extracts of the aerial and bulbous parts were obtained by hydroalcoholic maceration of the plant. Their antioxidant potentials were evaluated in vitro using four methods of 2,2-diphenyl-1picrylhydrazil (DPPH), 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP) assay, and total antioxidant capacity assay (TAC). The photoprotective properties were evaluated through the study of UVA and UVB absorbance and antityrosinase activity. The cytotoxic activity was determined against two breast cancer cell lines (MCF-7 and MDA-MB-231) and one human colorectal cancer cell line (HT-29) using the 3-[4,5-Dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) method. In addition, the antimicrobial activity was tested on six pathogens: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Staphylococcus aureus, and Candida albicans by using the disc diffusion method. Results: The results showed that the UVA and UVB absorptive proprieties of the extracts were similar to those used as positive controls: Methyl salicylate and zinc oxide. Moreover, the antioxidant and antityrosinase properties of the studied extracts were found to be weakly active. The extracts had strong cytotoxicity activities, especially against HT-29 cell line. However, the extracts did not show any antibacterial activity. Conclusion: According to the results of this study, the extracts can be used as a sunscreen to avoid dermal anomalies and as a new source of cytotoxic bioactive compound.

Photochemical studies of new synthetic derivatives of avobenzone under sunlight using UV-spectroscopy

Avobenzone is the most widely used chemical UV-A filter in sunscreen formulations and is prone to photodegradation under UV radiations/sunlight. Various methods have been employed to improve the photostability of avobenzone using triplet quenchers, antioxidants, and micelles. The current report has adopted a skeletal modification approach to improving the photostability of avobenzone. Electron-donating –OMe group has been replaced with electron-withdrawing –COOH/–COOMe group to yield the new derivatives, namely, avobenzone-acid/avobenzone-ester. New avobenzone derivatives were chemically synthesized and characterized using UV-spectroscopy which confirmed that they retained broad-spectrum UV-A filtering activity with additional UV-C filtering activity. Interestingly, the keto-form was present in crystals and 94:6 ratio of enol-: keto-forms were present in aprotic DMSO solvent confirming the occurrence of keto-enol tautomerization in avobenzone-acid. The photochemical properties of the new derivatives such as photostability, recovery from photodegraded enol forms in dark, and the effect of photostabilizer glutathione were accessed under sunlight using UV-spectroscopy. These studies indicate that the new derivatives compared to naïve avobenzone have improved photostability, rapid recovery from degradation products in the dark in DMSO, and enhanced response to photostabilizer glutathione. Computationally, Bond Dissociation Energy (BDE) and influence of DMSO solvent on the energetics of keto-enol tautomerizations of avobenzone and the new derivatives were calculated using density functional theory (DFT). These calculations support the experimental observations of the improved photochemical properties of the new avobenzone derivatives with retention of broad-spectrum UV-A absorbance activity. The current report has demonstrated that the skeletal modification approach has improved the intrinsic photostability of avobenzone and the new avobenzone derivatives may serve as a potential alternative to avobenzone in sunscreen lotions.

Graphene Quantum Dot-TiO2 Photonic Crystal Films for Photocatalytic Applications.

Photonic crystal structuring has emerged as an advanced method to enhance solar light harvesting by metal oxide photocatalysts along with rational compositional modifications of the materials’ properties. In this work, surface functionalization of TiO2 photonic crystals by blue luminescent graphene quantum dots (GQDs), n–π* band at ca. 350 nm, is demonstrated as a facile, environmental benign method to promote photocatalytic activity by the combination of slow photon-assisted light trapping with GQD-TiO2 interfacial electron transfer. TiO2 inverse opal films fabricated by the co-assembly of polymer colloidal spheres with a hydrolyzed titania precursor were post-modified by impregnation in aqueous GQDs suspension without any structural distortion. Photonic band gap engineering by varying the inverse opal macropore size resulted in selective performance enhancement for both salicylic acid photocatalytic degradation and photocurrent generation under UV–VIS and visible light, when red-edge slow photons overlapped with the composite’s absorption edge, whereas stop band reflection was attenuated by the strong UVA absorbance of the GQD-TiO2 photonic films. Photoelectrochemical and photoluminescence measurements indicated that the observed improvement, which surpassed similarly modified benchmark mesoporous P25 TiO2 films, was further assisted by GQDs electron acceptor action and visible light activation to a lesser extent, leading to highly efficient photocatalytic films.

Fucoxanthin for Topical Administration, a Phototoxic vs. Photoprotective Potential in a Tiered Strategy Assessed by In Vitro Methods.

Fucoxanthin possesses a well-described antioxidant activity that might be useful for human skin photoprotection. However, there is a lack of scientific information regarding its properties when applied onto human skin. Thus, the objective of the present study was to assess the photoprotective and phototoxicity potential of fucoxanthin based on its ultraviolet (UVB 280–320 nm; UVA 320–400 nm) and visible (VIS 400–700 nm) absorption, photostability, phototoxicity in 3T3 mouse fibroblast culture vs. full-thickness reconstructed human skin (RHS), and its ability to inhibit reactive oxygen species formation that is induced by UVA on HaCaT keratinocytes. Later, we evaluated the antioxidant properties of the sunscreen formulation plus 0.5% fucoxanthin onto RHS to confirm its bioavailability and antioxidant potential through the skin layers. The compound was isolated from the alga Desmarestia anceps. Fucoxanthin, despite presenting chemical photo-instability (dose 6 J/cm2: 35% UVA and 21% VIS absorbance reduction), showed acceptable photodegradation (dose 27.5 J/cm2: 5.8% UVB and 12.5% UVA absorbance reduction) when it was added to a sunscreen at 0.5% (w/v). In addition, it increased by 72% of the total sunscreen UV absorption spectra, presenting UV-booster properties. Fucoxanthin presented phototoxic potential in 3T3 fibroblasts (mean photo effect 0.917), but it was non-phototoxic in the RHS model due to barrier function that was provided by the stratum corneum. In addition, it showed a significant inhibition of ROS formation at 0.01% (p < 0.001), in HaCat, and in a sunscreen at 0.5% (w/v) (p < 0.001), in RHS. In conclusion, in vitro results showed fucoxanthin protective potential to the skin that might contribute to improving the photoprotective potential of sunscreens in vivo.

Epidermal UVA screening capacity measured in situ as an indicator of light acclimation state of leaves of a very plastic alpine plant Soldanella alpina L.

Soldanella alpina differing in leaf epidermal UV-A absorbance (DEA375), as measured with the Dualex, was investigated as a model alpine plant for the flavonoid (Flav) composition and concentration and for anatomical and pigment characteristics. In sun leaves, twenty-three flavones were characterised by their mass formula, their maximum absorption, their glycosylation, their methylation and dehydroxylation pattern. The flavones belonged to four subfamilies (tetra-hydroxy-flavones, penta-hydroxy-flavones, penta-hydroxy-methyl-flavones and tri-hydroxy-di-methoxy-flavones), abundant in sun and shade leaves. Their concentration was estimated by their absorption at 350 nm after HPLC separation. Sun leaves contained relatively higher contents of penta-hydroxy-methyl-flavones and shade leaves higher contents of tetra-hydroxy-flavones. The flavones were present mainly in vacuoles, all over the leaf. After shade-sun transfer, the content of most flavones increased, irrespective of the presence or absence of UV radiation. Highly significant correlations with the log-transformed DEA375 suggest that DEA375 can be readily applied to predict the flavone content of S. alpina leaves. Shade-sun transfer of leaves decreased the hydroxycinnamic acid (HCA) content, the mass-based chlorophyll (Chl) a+b content and the Chl/Carotenoid (Car) ratio but increased DEA375, and the Car content. Together with previously reported anatomical characteristics all these parameters correlated significantly with the DEA375. The Flav content is therefore correlated to most of the structural characteristics of leaf acclimation to light and this can be probed in situ by DEA375.

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.

2-Hydroxy-4-methoxybenzophenone Enhances the Suppression of Superoxide Anion Radicals Generated via UVA-induced Photosensitizing by t-Butyl Methoxydibenzoylmethane.

4-tert-Butyl-4'-methoxydibenzoylmethane (BMDM) is widely used throughout the world as a highly effective UVA absorber that can prevent the progression of photoaging in skin. However, due to its low photostability, BMDM is also known for the disadvantage of having a reduced capability to absorb UVA during prolonged exposure to sunlight. Although many studies have been carried out to overcome this disadvantage of BMDM, little attention has been paid to how the radicals generated from BMDM during UV exposure influence the skin. Therefore, the purpose of this study was twofold: One goal was to clarify the influence of radicals on human skin using cytotoxicity as a parameter. The second was to propose a solution that could reduce the radical formation while taking photostability into consideration. Using ESR spin trapping and superoxide dismutase (SOD) treatment, the radicals produced by the UV exposure of BMDM were shown to be superoxide anion radicals (•O2-). HaCaT keratinocytes exposed to UVA in the presence of BMDM showed a significant reduction in cell viability, indicating that the radicals produced from BMDM have a harmful influence on the skin. UVA exposure coincidently led to a reduction of UVA absorbance by BMDM. Interestingly, 2-hydroxy-4-methoxybenzophenone (Benzophenone-3; BP3) reduced both the radical formation and the cytotoxicity resulting from the UVA-exposure of BMDM, while also restoring its UVA absorbance. In conclusion, the results show that BMDM and BP3 is an effective combination to reduce the influence of UVA-exposed BMDM on the skin and to prevent the loss of UVA absorbance by BMDM during UV exposure.

Ultraviolet Protection Properties of Commercial Sunscreens and Sunscreens Containing Zno Nanorods

Zinc oxide nanorods were used as the main ultraviolet agent in the development of sunscreens. Four commercial sunscreens containing organic and inorganic UV agents were studied for their UV performances and SPF determinations. From FESEM and TEM micrographs of ZnO powder, the dominant structure was rod structure with width range 61-70 nm. Sunscreens containing different concentrations of ZnO nanorods were characterized using UV-Vis spectrophotometer and X-ray diffraction (XRD). The absorbance spectra for commercial sunscreens showed a good protection in range of UVB (280-320nm), while sunscreens containing 20-40% (weight percentage) of ZnO nanorods showed a greater UV absorbance in UVA and UVB (280-400 nm). The strong UVA absorbance of ZnO nanorod can offer extra UV protection for commercial sunscreens. The average crystallite sizes of the sunscreen samples calculated from the XRD spectra were in the range 45.27 to 47.36 nm. In vitro sun protection factor (SPF) method was carried out to determine the SPF value of sunscreen specimens. SPF values of sunscreens containing ZnO nanorods were 29.50 to 43.48, whereby these SPF values indicated more than 93% of UVB blocking capability. The SPF values found of commercial sunscreens were slightly different from the SPF values in the product labels. In conclusion, incorporation of ZnO nanorods into sunscreen can greatly enhanced the UV blocking performance of sunscreens.

Understanding sunscreen SPF performance using cross-polarized UVA reflectance photography.

Objective methods for understanding sunscreen behaviour invitro before they are applied to the skin have failed to keep pace with the ever-increasing demands for higher SPF scores where the products are absorbing more and more similar levels of UV. A novel method for visualizing the spreading and location of SPF ingredients based on cross-polarized UVA reflectance photography is described here which gives new insights into the formation of final film morphology and how it correlates with invivo SPF efficacy for a set of test products. High-resolution UVA-based images of sunscreen films spread onto PMMA plates were captured using a modified commercial SLR camera in a custom imaging system. Visual grading and image analysis were used to describe the overall UVA absorbance and streakiness of the resultant films, and the data compared with both invivo and calculated invitro SPF scores for the products. Differences were observed between the products in terms of how they spread during application. A strong correlation was observed between the evenness of the resultant film as determined from the photographs and final invivo SPF scores. Cross-polarized UVA reflectance photography has been demonstrated to be a valuable new method for assessing sunscreen distribution after spreading and to differentiate product based on film morphology, as well as strongly correlating with final invivo behaviour.

In vivo epidermal UV-A absorbance is induced by sunlight and protects Soldanella alpina leaves from photoinhibition.

Alpine plants like Soldanella alpina L. are subjected to high PAR and high UV radiation. Among the important photoprotective mechanisms that prevent photoinhibition under such conditions, passive optical barriers such as UV-absorbing compounds were investigated. In this study, temporal and spatial patterns of epidermal UV-A absorbance for S. alpina leaves were investigated with a combination of absorbance measurements at 375nm and imaging methods. UV-A absorbance was highest in plants acclimated to full sunlight and was markedly stable during the leaves' lifetime. UV-A absorbance was correlated with leaf structure (leaf mass per area ratio, density of epidermal cells and stomata) and biochemical features such as chlorophyll and carotenoid content and ratio, which are characteristics of light acclimation. UV-A-absorbing compounds were mainly localised in the epidermal vacuoles and trichomes. Leaves with low UV-A absorbance were significantly more photosensitive than leaves with high UV-A absorbance. However, the epidermal UV-A absorbance increased in low-absorbance leaves under full sunlight even in the absence of UV radiation. Results suggest that high epidermal UV-A absorbance protects S. alpina leaves from photoinactivation, which is especially important after snowmelt, when plants are suddenly exposed to full sunlight.

Epidermal UV-A absorbance and whole-leaf flavonoid composition in pea respond more to solar blue light than to solar UV radiation.

Plants synthesize phenolic compounds in response to certain environmental signals or stresses. One large group of phenolics, flavonoids, is considered particularly responsive to ultraviolet (UV) radiation. However, here we demonstrate that solar blue light stimulates flavonoid biosynthesis in the absence of UV-A and UV-B radiation. We grew pea plants (Pisum sativum cv. Meteor) outdoors, in Finland during the summer, under five types of filters differing in their spectral transmittance. These filters were used to (1) attenuate UV-B; (2) attenuate UV-B and UV-A < 370 nm; (3) attenuate UV-B and UV-A; (4) attenuate UV-B, UV-A and blue light; and (5) as a control not attenuating these wavebands. Attenuation of blue light significantly reduced the flavonoid content in leaf adaxial epidermis and reduced the whole-leaf concentrations of quercetin derivatives relative to kaempferol derivatives. In contrast, UV-B responses were not significant. These results show that pea plants regulate epidermal UV-A absorbance and accumulation of individual flavonoids by perceiving complex radiation signals that extend into the visible region of the solar spectrum. Furthermore, solar blue light instead of solar UV-B radiation can be the main regulator of phenolic compound accumulation in plants that germinate and develop outdoors.

New noninvasive approach assessing in vivo sun protection factor (SPF) using diffuse reflectance spectroscopy (DRS) and in vitro transmission

In the past 56 years, many different in vitro methodologies have been developed and published to assess the sun protection factor (SPF) of products, but there is no method that has 1:1 correlation with in vivo measurements. Spectroscopic techniques have been used to noninvasively assess the UVA protection factor with good correlation to in vivo UVA-PF methodologies. To assess the SPF of sunscreen product by diffuse reflectance spectroscopy (DRS) technique, it is necessary to also determine the absorbance spectrum of the test material in the UVB portion of the spectrum (290-320 nm). However, because of the high absorbance characteristics of the stratum corneum and epidermis, the human skin does not remit enough UVB radiation to be used to measure the absorption spectrum of the applied product on skin. In this work, we present a new method combining the evaluation of the absolute UVA absorption spectrum, as measured by DRS with the spectral absorbance 'shape' of the UVB absorbance of the test material as determined with current in vitro thin film spectroscopy. The measurement of the in vivo UVA absorption spectrum involves the assessment of the remitted intensity of monochromatic UVA radiation (320-400 nm) before and after a sunscreen product was applied on skin using a spectrofluorimeter Fluorolog 3, FL3-22 (Yvon Horiba, Edison, NJ, USA). The probe geometry assures that light scattering products as well as colored products may be correctly assessed. This methodology has been extensively tested, validated, and reported in the literature. The in vitro absorption spectrum of the sunscreen samples and polyvinyl chloride (PVC) films 'surrogate' sunscreen standards were measured using Labsphere® UV-2000S (Labsphere, North Sutton, NH, USA). Sunscreens samples were tested using PMMA Helioplates (Helioscience, Marseille, France) as substrates. The UVB absorbance spectrum (Labsphere) is 'attached' to the UVA absorbance spectrum (diffuse reflectance) with the UVB absorbance matched to the UVA absorbance at 340 nm to complete the full spectral absorbance from which an estimate the SPF of the product can be calculated. Seventeen test materials with known in vivo SPF values were tested. Two of the tested products were PVC sunscreen thin films with 10-15 micrometers thickness and were used to investigate the absorption spectrum of these films when applied on different reflectance surfaces. Similar to the human in vivo SPF test, the developed methodology suggests limiting the use on Fitzpatrick skin phototypes I to III. The correlation of this new method with in vivo clinical SPF values was 0.98 (r2) with a slope of 1.007. This new methodology provides a new approach to determine SPF values without the extensive UV irradiation procedures (and biological responses) currently used to establish sunscreen efficacy. Further work will be conducted to establish methods for evaluation of products that are not photostable.

Dénervation ventrale de la hanche associée à une myectomie du pectiné chez le chien : étude rétrospective sur 52 cas

Flavonoids are secondary plant metabolites assumed to have beneficial effects on human health. In this study, chlorophyll fluorescence (ChlF) was tested as a tool for non-destructive estimation of the flavonoid content in the skin of apples (Malus domestica Borkh., cv. Aroma). The method is based on the comparison of ChlF signals obtained with excitation beams absorbed and not absorbed by the various flavonoids. The use of three excitation beams allowed us to measure the total flavonoid content and the content of anthocyanins separately. The ChlF measurements were performed directly on the apple skin with portable fluorometers inducing ChlF with UV-A radiation at 375 nm (F(UV)), blue light at 470 nm (F(B)) and red light at 655 nm (F(R)). The relative absorbance of UV-A radiation was calculated as log[F(R)/F(UV)], whereas the relative absorbance of blue light was calculated as log[F(R)/F(B)]. For reference, the same area of the apple as subjected to the ChlF measurements was used for analysis of phenolic compounds by HPLC and reflectance spectra recordings. To determine the localisation of flavonoids in the apple skin, cross sections of the outer cell layers were examined under epifluorescence microscopy. The flavonoids were mostly concentrated in the epidermis above the chlorophyll. This distribution is in agreement with the prerequisites of the ChlF method. The relative UV-A absorbance calculated from ChlF measurements was well correlated with the total flavonoid content detected with HPLC (r2 = 0.899, P < 0.001). The relative blue light absorbance calculated from ChlF measurements was linearly correlated to the content of anthocyanins quantified with both HPLC (r2 = 0.889, P < 0.001) and reflectance measurements (r2 = 0.917, P < 0.001). In conclusion, ChlF measurements can indeed be utilised for non-destructive estimation of both anthocyanins and total flavonoids in apples and can in this context function as a valuable tool for the commercial fruit industry as well as in plant and food research.

Propolis as potential cosmeceutical sunscreen agent for its combined photoprotective and antioxidant properties

Propolis, bee glue, and its main polyphenolic components show high antioxidant activity as found measuring their inhibitory action on lipid peroxidation of linoleic acid (LA) in sodium dodecyl sulfate (SDS) micelles. Furthermore, these substances evidence effectiveness as broad spectrum UVB and UVA photoprotection sunscreens, as it results by measurements of sun protection factor (SPF), the universal indicator related primarily to UVB radiations, and of the two parameters giving an indication of the UVA absorbance properties, i.e. UVA/UVB ratio and critical wavelength. The combination of these characteristics moves up propolis and its main polyphenolic components to the class of cosmeceuticals, as possible active ingredient of sunscreen commercial formulations for their protective and preventive properties.

Effects of Urbanization on Organic Carbon Loads in the Sacramento River, California

To gain better understanding of the effects of urbanization on organic matter transport in rivers, we quantified total organic carbon loading from point and non‐point urban sources within the metropolitan area of Sacramento and compared these loads to the amount of organic carbon carried in the downstream Sacramento River. Median total organic carbon (TOC) concentrations in the Sacramento River, non‐point urban runoff and wastewater treatment plant effluent were 2.1, 8.9, and 23 mg L−1, respectively. Dissolved organic carbon (DOC) in non‐point runoff and the river had similar specific UVA absorbance and disinfection by‐product formation potential, but based on radiocarbon measurements, non‐point DOC was substantially older (age &gt; 2000 a) than DOC in the Sacramento River. This finding suggests that DOC in non‐point runoff is derived primarily from leaching of older soil organic matter. The 10th, 50th, 90th and 99th percentile contributions of urban sources to daily TOC load in the Sacramento River were 10%, 20%, 38% and 80%, respectively. Total urban TOC yield was 150 kg ha−1yr−1 and urban sources contributed ∼17% of the annual load of TOC in the Sacramento River below Sacramento.

UV screening in higher plants induced by low temperature in the absence of UV-B radiation

Epidermally located UV-B absorbing hydroxycinnamic acid derivatives and flavonoids serve as a screen against potentially damaging UV-B (280-315 nm) radiation in higher plants. We investigated the effect of low temperature on epidermal screening as assessed by a chlorophyll fluorescence technique. The epidermal UV-transmittance of greenhouse-grown Vicia faba plants was strongly dependent on growth temperatures between 21 and 9 degrees C, with significant differences already between 21 and 18 degrees C. There was a good correlation between epidermal UV-A and UV-B absorbance and the absorbance of whole leaf extracts at the respective wavelengths. Whereas in Oxyria digyna and Rumex longifolius no temperature dependence of epidermal transmittance could be detected, it was confirmed for seven other crop plant species, including summer and winter varieties, and for Arabidopsis thaliana. Dicotyledoneous plants showed a stronger response than monocotyledoneous ones. In all investigated species, the response in the UV-A spectral region was similar to that in the UV-B, suggesting that flavonoids were the responsible compounds. In V. faba, mature leaves did not respond with a change in epidermal transmittance upon transfer from warm to cool conditions or vice versa, whereas developing leaves did acclimate to the new conditions. We conclude that temperature is an important determinant of the acclimation of epidermal UV transmittance to environmental conditions in many plant species. The potential adaptive value of this response is discussed.

Chlorophyll fluorescence as a tool for non-destructive estimation of anthocyanins and total flavonoids in apples

Flavonoids are secondary plant metabolites assumed to have beneficial effects on human health. In this study, chlorophyll fluorescence (ChlF) was tested as a tool for non-destructive estimation of the flavonoid content in the skin of apples ( Malus domestica Borkh., cv. Aroma). The method is based on the comparison of ChlF signals obtained with excitation beams absorbed and not absorbed by the various flavonoids. The use of three excitation beams allowed us to measure the total flavonoid content and the content of anthocyanins separately. The ChlF measurements were performed directly on the apple skin with portable fluorometers inducing ChlF with UV-A radiation at 375 nm ( F(UV)), blue light at 470 nm ( F(B)) and red light at 655 nm ( F(R)). The relative absorbance of UV-A radiation was calculated as log[ F(R)/ F(UV)], whereas the relative absorbance of blue light was calculated as log[ F(R)/ F(B)]. For reference, the same area of the apple as subjected to the ChlF measurements was used for analysis of phenolic compounds by HPLC and reflectance spectra recordings. To determine the localisation of flavonoids in the apple skin, cross sections of the outer cell layers were examined under epifluorescence microscopy. The flavonoids were mostly concentrated in the epidermis above the chlorophyll. This distribution is in agreement with the prerequisites of the ChlF method. The relative UV-A absorbance calculated from ChlF measurements was well correlated with the total flavonoid content detected with HPLC ( r 2 = 0.899, P < 0.001). The relative blue light absorbance calculated from ChlF measurements was linearly correlated to the content of anthocyanins quantified with both HPLC ( r 2 = 0.889, P < 0.001) and reflectance measurements ( r 2 = 0.917, P < 0.001). In conclusion, ChlF measurements can indeed be utilised for non-destructive estimation of both anthocyanins and total flavonoids in apples and can in this context function as a valuable tool for the commercial fruit industry as well as in plant and food research.

Comparison of the Effects of Sonolysis and γ-Radiolysis on Dissolved Organic Matter

The effects of 640 kHz sonolysis and 60Co gamma-radiolysis on dissolved organic matter (DOM) were compared through UV/ vis absorption spectrometric, dissolved organic carbon concentration ([DOC]), and potentiometric titration analyses. A reverse-phase chromatographic technique was used to compare changes in the DOM hydrophobicity distribution, and a size exclusion chromatographic technique with inline UV-A absorbance, fluorescence, and [DOC] detectors was used to compare changes in the DOM molecular weight distribution. Whereas upon radiolysis major decreases in absorbance and [DOC] were induced and near-total DOC removal was achieved, upon sonolysis there were major decreases in UV/vis absorbance but only minor decreases in [DOC], and a substantial quantity of hydrophilic nonchromophoric material remained in solution. In radiolysis, hydrophilic and hydrophobic DOM solution components were exposed to equal hydroxyl radical (*OH) concentrations. However, in sonolysis, hydrophobic DOM components were exposed to more elevated *OH concentrations than the hydrophilic components and consequently had enhanced rates of degradation. Sonolysis may be of interest in the design of advanced oxidation processes in which the selective elimination of hydrophobic solution components, such as hydrophobic organic contaminants and hydrophobic DOM domains into which they partition, is desired.

Photochemical behavior of a new long-chain UV absorber derived from 4-tert-butyl-4'-methoxydibenzoylmethane.

A new UV filter, the 1-(4-tert-butylphenyl)-2-decanyl-3-(4'-methoxyphenyl)-propane-1,3-dione, called C10-DBM, was prepared by grafting a 10-carbon aliphatic chain to the alpha-carbonyl position of 4-tert-butyl-4'-methoxydibenzoylmethane (BM-DBM), a well-known and often used UV filter. The UV-A absorption efficiency of organic solutions containing the new filter was tested and compared with identical solutions containing BM-DBM with or without irradiation (xenon lamp). The originality of this new filter is that its UV-A absorbance appeared during irradiation of the molecule. Although the molar absorption coefficient of C10-DBM in the UV-A domain was lower than that of BM-DBM, the solutions absorption exhibited a much more photostable behavior under irradiation. In this study, we first demonstrated that C10-DBM was a precursor of BM-DBM (enol isomer) by means of high-performance liquid chromatography followed by mass spectrometry. Indeed, we showed that the UV-A absorption of C10-DBM solutions appearing during the irradiation of the molecule was due to a Norrish-II reaction (beta-cleavage), which induced the release of the BM-DBM enol form and 1-decene. Then, we established a kinetic model for the photochemistry of C10-DBM and fitted the variation of UV absorption spectra to confirm the proposed mechanism.

UV-excited chlorophyll fluorescence as a tool for the assessment of UV-protection by the epidermis of plants.

Recently, a new method for estimating epidermal transmission of UV radiation in higher plants has been proposed. The empirical evidence for the usefulness of this method is reviewed here. Direct comparison with spectroscopically determined epidermal transmission yielded equivalent results. A linear correlation to the concentration of epidermal screening compounds has been shown. Relating UV-A and UV-B absorbance allowed some preliminary conclusions about the chemical nature of the screening compounds. A new portable apparatus is presented for the first time, which allows the non-destructive assessment of UV-A screening even under field conditions. Repeated measurements on identical leaves over a time-course of 6 d demonstrated a strong age-dependence in the capacity for the synthesis of UV-A screening compounds upon exposure to UV-B radiation. It is concluded that the new method may provide a valuable tool for the investigation of the acclimation of plants to UV-B radiation and, when accompanied by HPLC analysis, of the reaction of phenolic metabolism to environmental stimuli.