Long-wavelength UVA Research Articles

Helosciadium crassipes Koch (Apiaceae) extracts as natural sunscreen and preservative additives

Recently, ingredients derived from natural sources have gained increasing interest in the cosmetic field due to their low toxicity. Therefore, this study was designed to explore the cosmetic potential of Helosciadium crassipes Koch (Apiaceae) species growing in Algeria as a promising natural preservative and broad-spectrum UV protection additive. In our study, the in-vitro antioxidant effect was assessed via DPPH radical scavenging and total antioxidant capacity by phosphomolybdenum method (TAC), while the protection against UVB radiation was evaluated according to the sun protection factor (SPF) by using UV spectroscopic technic at wavelengths ranging from 290 to 320 nm and Mansur’s equation, for the photoprotective effect against long-wavelength UVA, UVA/UVB and critical wavelength (λc) parameters were evaluated. The outcomes showed that among the tested extracts, the methanolic extract (MeOH) contains high levels of phenolics and flavonoids, and possesses a significant antioxidant effect, particularly in DPPH radical scavenging assay. Similarly, this last one exhibited high photoprotective activity in UVB and UVA ranges. The gathered results reveal the possibility of using this extract as a good natural additive to be incorporated into cosmetic formulations as a broad-spectrum UV protection candidate and as a preservative agent.

Photoprotective Agents Obtained from Aromatic Plants Grown in Colombia: Total Phenolic Content, Antioxidant Activity, and Assessment of Cytotoxic Potential in Cancer Cell Lines of Cymbopogon flexuosus L. and Tagetes lucida Cav. Essential Oils.

Photoprotective agents obtained from plants provide benefits for the health of the skin. The present study aims to assess the total phenolic content (TPC) and in vitro UV-protective properties of twelve essential oils (EOs) from plants grown in Colombia and to evaluate the antioxidant and cytotoxic potential of two species identified as photoprotective potentials: Cymbopogon flexuosus and Tagetes lucida. The composition of EOs was studied by GC/MS. The cytotoxicity of both EOs was examined using an MTT assay, and an H2-DCFDA probe was employed to estimate the intracellular production of ROS in HepG2 and Calu-1 cells. Major constituents (≥10%) were neral, geranial, geranyl acetate in C. flexuosus and estragole in T. lucida. The TPC for C. flexuosus and T. lucida EOs were ≥10 mg GAE/g of byproduct. Both EOs showed photoprotective properties (SPFin vitro: 13–14), and long-wavelength UVA protection (λc > 370 nm). HepG2 and Calu-1 cells exposed to C. flexuosus exhibited antiproliferative activity (˂50%) at 125 µg/mL, while T. lucida was at 250 and 500 µg/mL. The IC50 values for C. flexuosus were 75 and 100 µg/mL in HepG2 and Calu-1 cells, respectively, whereas those for T. lucida were >250 µg/mL. These EOs achieved significant inhibitory effects (between 15.6 and 40.4%) against H2O2-induced oxidative stress. The results showed that EO compounds recognized as antioxidants could counteract the effects elicited by H2O2.

Long-wavelength UVA enhances UVB-induced cell death in cultured keratinocytes: DSB formation and suppressed survival pathway.

Solar UV radiation consists of both UVA and UVB. The wavelength-specific molecular responses to UV radiation have been studied, but the interaction between UVA and UVB has not been well understood. In this study, we found that long-wavelength UVA, UVA1, augmented UVB-induced cell death, and examined the underlying mechanisms. Human keratinocytes HaCaT were exposed to UVA1, followed by UVB irradiation. Irradiation by UVA1 alone showed no effect on cell survival, whereas the UVA1 pre-irradiation remarkably enhanced UVB-induced cell death. UVA1 delayed the repair of pyrimidine dimers formed by UVB and the accumulation of nucleotide excision repair (NER) proteins to damaged sites. Gap synthesis during NER was also decreased, suggesting that UVA1 delayed NER, and unrepaired pyrimidine dimers and single-strand breaks generated in the process of NER were left behind. Accumulation of this unrepaired DNA damage might have led to the formation of DNA double-strand breaks (DSBs), as was detected using gel electrophoresis analysis and phosphorylated histone H2AX assay. Combined exposure enhanced the ATM-Chk2 signaling pathway, but not the ATR-Chk1 pathway, confirming the enhanced formation of DSBs. Moreover, UVA1 suppressed the UVB-induced phosphorylation of Akt, a survival signal pathway. These results indicated that UVA1 influenced the repair of UVB-induced DNA damage, which resulted in the formation of DSBs and enhanced cell death, suggesting the risk of simultaneous exposure to high doses of UVA1 and UVB.

Spacer-Mediated Control of Coumarin Uncaging for Photocaged Thymidine.

Despite its importance in the design of photocaged molecules, less attention is focused on linker chemistry than the cage itself. Here, we describe unique uncaging properties displayed by two coumarin-caged thymidine compounds, each conjugated with (2) or without (1) an extended, self-immolative spacer. Photolysis of 1 using long-wavelength UVA (365 nm) or visible (420, 455 nm) light led to the release of free thymidine along with the competitive generation of a thymidine-bearing recombination product. The occurrence of this undesired side reaction, which is previously unreported, was not present with the photolysis of 2, which released thymidine exclusively with higher quantum efficiency. We propose that the spatial separation between the cage and the substrate molecule conferred by the extended linker can play a critical role in circumventing this unproductive reaction. This report reinforces the importance of linker selection in the design of coumarin-caged oligonucleosides and other conjugates.

The effect of postharvest ultraviolet irradiation on the content of antioxidant compounds and the activity of antioxidant enzymes in tomato

The effect of different doses of long-wavelength UV-A (320 nm–400nm) irradiation on physicochemical and antioxidant characteristics of tomatoes grown on the territory of the Russian Federation was studied. The obtained results show that this kind of processing does not cause deterioration of qualitative parameters of vegetables (texture, color, soluble solids content, titratable acidity). It was established that the total content of phenolic compounds, carotenoids and flavonoids increases (p-value<0.05) in tomatoes at all the investigated wavelengths (353 nm, 365 nm and 400 nm), while the content of chlorophylls reacts ambiguously: at some wavelengths, it increases, at other, it decreases. The maximum increase in antioxidant activity, as compared to untreated samples, is observed in tomatoe samples irradiated for 360 min within the range of 365 nm. For different types of tomatoes, the increment for common content of phenolic compounds is – 42.9–55.0 %, carotenoids – 24.0–56.0 %, flavonoids – 28.0–33.0 %, β-carotene – 70.9–71.6 %, lycopene – 62.6–69.0 %, lutein – 64.8–72.0 % from original. The studies reveal some potential of post-harvest ultraviolet irradiation (A-range) of tomatoes to increase their antioxidant activity. However, more research is needed to confirm this fact and the possibility to develop some technology.

EXPERIMENTAL TESTING OF AN IN VIVO METHOD OF PHOTOTOXICITY EVALUATION

At present all new medicinal products and cosmetics that absorb medium-wavelength UVB, long-wavelength UVA, or visible light in the range 290–700 nm need to be tested for potential phototoxicity. phototoxicity is evaluated by both in vitro and in vivo methods. There are guidelines for in vitro phototoxicity evaluation, however, there are no formally validated protocols for in vivo phototoxicity evaluation. The purpose of this study was to test an economically viable and informative method for in vivo evaluation of tetracycline and ketorolac phototoxicity using outbred rats. Two medicinal products potentially capable of causing clinically established phototoxic reactions were used in this study: tetracycline (tablets, 200 mg/kg and 300 mg/kg) and ketorolac (gel, 13.4 mg/kg, 26.8 mg/kg and 40.3 mg/kg). The medicines were administered in both single and multiple doses. Ultraviolet irradiator OUFK-03 (OOO «Solnyshko», Russia) was used as a light source. The UV exposure (5 J/cm2 and 15 J/cm 2 ) was performed once 1 h after medicine administration. The skin reaction was evaluated 30 minutes and 24 hours after irradiation and then daily for 2 weeks. As a result, the following optimal parameters were determined for in vivo evaluation of phototoxic reactions caused by the medicines: radiation intensity — 15 J/cm 2 for single systemic administration and 5 J/cm 2 for single topical (dermal) administration; recommended period of skin reaction evaluation for outbred rats is not less than 7 days.

A Thioacetal Photocage Designed for Dual Release: Application in the Quantitation of Therapeutic Release by Synchronous Reporter Decaging.

Despite the immense potential of existing photocaging technology, its application is limited by the paucity of advanced caging tools. Here, we report on the design of a novel thioacetal ortho-nitrobenzaldehyde (TNB) dual arm photocage that enabled control of the simultaneous release of two payloads linked to a single TNB unit. By using this cage, which was prepared in a single step from commercial 6-nitroverataldehyde, three drug-fluorophore conjugates were synthesized: Taxol-TNB-fluorescein, Taxol-TNB-coumarin, and doxorubicin-TNB-coumarin, and long-wavelength UVA light-triggered release experiments demonstrated that dual payload release occurred with rapid decay kinetics for each conjugate. In cell-based assays performed in vitro, dual release could also be controlled by UV exposure, resulting in increased cellular fluorescence and cytotoxicity with potency equal to that of unmodified drug towards the KB carcinoma cell line. The extent of such dual release was quantifiable by reporter fluorescence measured in situ and was found to correlate with the extent of cytotoxicity. Thus, this novel dual arm cage strategy provides a valuable tool that enables both active control and real-time monitoring of drug activation at the delivery site.

Extracellular Polysaccharide Production in a Scytonemin-Deficient Mutant of Nostoc punctiforme Under UVA and Oxidative Stress.

Some cyanobacteria can protect themselves from ultraviolet radiation by producing sunscreen pigments. In particular, the sheath pigment scytonemin protects cells against long-wavelength UVA radiation and is only found in cyanobacteria which are capable of extracellular polysaccharide (EPS) production. The presence of a putative glycosyltransferase encoded within the scytonemin gene cluster, along with the localization of scytonemin and EPS to the extracellular sheath, prompted us to investigate the relationship between scytonemin and EPS production under UVA stress. In this study, it was hypothesized that there would be a relationship between the biosynthesis of scytonemin and EPS under both UVA and oxidative stress, since the latter is a by-product of UVA radiation. EPS production was measured following exposure of wild-type Nostoc punctiforme and the non-scytonemin-producing strain SCY59 to UVA and oxidative stress. Under UVA, SCY59 produced significantly more EPS than the unstressed controls and the wild type, while both strains produced more EPS under oxidative stress compared to the controls. The results suggest that EPS secretion occurs in response to the oxidative stress by-product of UVA rather than as a direct response to UVA radiation.

Solar Irradiance Changes and Phytoplankton Productivity in Earth's Ocean Following Astrophysical Ionizing Radiation Events.

Two atmospheric responses to simulated astrophysical ionizing radiation events significant to life on Earth are production of odd-nitrogen species, especially NO2, and subsequent depletion of stratospheric ozone. Ozone depletion increases incident short-wavelength ultraviolet radiation (UVB, 280-315 nm) and longer (>600 nm) wavelengths of photosynthetically available radiation (PAR, 400-700 nm). On the other hand, the NO2 haze decreases atmospheric transmission in the long-wavelength UVA (315-400 nm) and short-wavelength PAR. Here, we use the results of previous simulations of incident spectral irradiance following an ionizing radiation event to predict changes in terran productivity focusing on photosynthesis of marine phytoplankton. The prediction is based on a spectral model of photosynthetic response, which was developed for the dominant genera in central regions of the ocean (Synechococcus and Prochlorococcus), and on remote-sensing-based observations of spectral water transparency, temperature, wind speed, and mixed layer depth. Predicted productivity declined after a simulated ionizing event, but the effect integrated over the water column was small. For integrations taking into account the full depth range of PAR transmission (down to 0.1% of utilizable PAR), the decrease was at most 2-3% (depending on strain), with larger effects (5-7%) for integrations just to the depth of the surface mixed layer. The deeper integrations were most affected by the decreased utilizable PAR at depth due to the NO2 haze, whereas shallower integrations were most affected by the increased surface UV. Several factors tended to dampen the magnitude of productivity responses relative to increases in surface-damaging radiation, for example, most inhibition in the modeled strains is caused by UVA and PAR, and the greatest relative increase in damaging exposure is predicted to occur in the winter when UV and productivity are low.

Prevention of melasma relapses with sunscreen combining protection against UV and short wavelengths of visible light: A prospective randomized comparative trial

Prevention of melasma relapses with sunscreen combining protection against UV and short wavelengths of visible light: A prospective randomized comparative trial

UVA (UVA-1) therapy for the treatment of acute GVHD of the skin

Long-wavelength UVA (340-400 nm UVA-1) phototherapy has been reported to be effective in atopic dermatitis, localized scleroderma and T-cell-derived skin diseases. We retrospectively investigated 70 patients with acute cutaneous GVHD after allogeneic haematopoietic cell transplantation or donor lymphocyte infusion. Complete and partial responses with a median duration of 10 months were achieved in 49 (70%) and 17 (24.3%) patients, respectively. Overall, 47 (67.1%) patients were not treated with systemic steroids. Furthermore, immunosuppression could be tapered in 24 (34.3%) patients while they were receiving UVA-1 treatment. Responses were seen irrespective of age or type of conditioning. Treatment was very well tolerated. After a median follow-up of 18 (range 10-60) months, three patients developed epithelial skin neoplasia. We conclude that UVA-1 therapy is feasible, well tolerated and can be an effective treatment for acute GVHD of the skin, thereby avoiding the use of systemic steroids and/or allowing a more rapid tapering of systemic immunosuppression in a substantial number of patients. The results of this retrospective analysis warrant larger, prospective studies and the effectiveness of UVA-1 therapy should be compared with other established treatment modalities.

Skin cell protection against UVA by Sideroxyl, a new antioxidant complementary to sunscreens

Oxidative stress resulting from photosensitized ROS production in skin is widely accepted as the main contributor to the deleterious effects of UVA exposure. Among the mechanisms known to be involved in UVA-induced oxidative damage, iron plays a central role. UVA radiation of skin cells induces an immediate release of iron, which can then act as a catalyst for uncontrolled oxidation reactions of cell components. Such site-specific damage can scarcely be counteracted by classical antioxidants. In contrast, iron chelators potentially offer an effective way to protect skin against UVA insults. However, iron chelation is very difficult to achieve without disturbing iron homeostasis or inducing iron depletion. A novel compound was developed to avoid these potentially harmful side effects. Sideroxyl was designed to acquire its strong chelating capability only during oxidative stress according to an original process of intramolecular hydroxylation. Herein, we describe in vitro results demonstrating the protective efficiency of Sideroxyl against deleterious effects of UVA at the molecular, cellular, and tissular levels. First, the Sideroxyl diacid form protects a model protein against UVA-induced photosensitized carbonylation. Second, intracellular ROS are dose-dependently decreased in the presence of Sideroxyl in both human cultured fibroblasts and human keratinocytes. Third, Sideroxyl protects normal human fibroblasts against UVA-induced DNA damage as measured by the comet assay and MMP-1 production. Finally, Sideroxyl provides protection against UVA-induced alterations in human reconstructed skin. These results suggest that Sideroxyl may prevent UVA-induced damage in human skin as a complement to sunscreens, especially in the long-wavelength UVA range.

Impact of Long-Wavelength UVA and Visible Light on Melanocompetent Skin

The purpose of this study was to determine the effect of visible light on the immediate pigmentation and delayed tanning of melanocompetent skin; the results were compared with those induced by long-wavelength UVA (UVA1). Two electromagnetic radiation sources were used to irradiate the lower back of 20 volunteers with skin types IV-VI: UVA1 (340-400 nm) and visible light (400-700 nm). Pigmentation was assessed by visual examination, digital photography with a cross-polarized filter, and diffused reflectance spectroscopy at 7 time points over a 2-week period. Confocal microscopy and skin biopsies for histopathological examination using different stains were carried out. Irradiation was also carried out on skin type II. Results showed that although both UVA1 and visible light can induce pigmentation in skin types IV-VI, pigmentation induced by visible light was darker and more sustained. No pigmentation was observed in skin type II. The quality and quantity of pigment induced by visible light and UVA1 were different. These findings have potential implications on the management of photoaggravated pigmentary disorders, the proper use of sunscreens, and the treatment of depigmented lesions.

Response of Antarctic phytoplankton to solar UVR exposure: inhibition and recovery of photosynthesis in coastal and pelagic assemblages

We examined ultraviolet radiation (UVR)-in- duced inhibition and recovery of Antarctic phytoplankton photosynthesis during the austral spring in surface coastal waters near Palmer Stn and in the open ocean waters of the Weddell-Scotia Confluence from 1997 to 1999. Pri- mary productivity was measured in 12 h time-course ex- periments using enclosures that transmitted either full- spectrum solar UVR or only long-wavelength UVA. Recovery from inhibition was determined by transferring samples from high to low UVR at intervals during the in- cubation. Biological weighting functions for UVR inhibi- tion of photosynthesis were also determined for each experiment. Photosynthesis measurements were compared to model predictions using 3 exposure-response relation- ships: an irradiance-based (E) model that assumes rapid repair, a cumulative-exposure (H) model that assumes no repair, and a model that incorporated slow repair (R model). Open-ocean phytoplankton were generally much more sensitive to UVR inhibition than coastal assem- blages, which primarily had high rates of repair (E model). In contrast, open-ocean assemblages generally recovered from inhibition more slowly (R model). Some recovery was evident in all cases, so the H model was not applied to any assemblage. Our previous view of repair being either sim- ply present or absent is therefore revised to recognize that repair rates range from slow to fast and should be taken into account, together with spectral weight, in assess- ments of photosynthetic response to UVR in the Southern Ocean, including the effect of ozone depletion. Informa- tion on repair rate is particularly important for simulations of production in vertically mixed surface layers.

Estudio epidemiológico de la PUVAterapia en la comunidad valenciana

Background Photochemotherapy with 8-methoxypsoralen and long-wavelength UV-A (PUVA) has been extensively used for the treatment of various skin diseases since its approval in 1982 by the US Food and Drug Administration. Methods A retrospective study was performed of patients treated with PUVA, including topical and systemic treatment, over a period of 14 years. All patients were treated using a standard PUVA therapy regimen. Results A total of 877 patients were analyzed for the period 1982 to 1996. Forty-one skin diseases were treated, including 341 cases of psoriasis and 71 cutaneous T-cell lymphomas. The aim of the study was to describe the characteristics of the patients treated with PUVA therapy during that period and compare the results with those observed in other regions. Conclusions Although PUVA therapy is widely used in a large number of countries for the treatment of various skin diseases, few studies have described the characteristics of the patients and the differences in the parameters of PUVA according to the disease.

Photodynamic Therapy Resistant Human Colon Carcinoma HT29 Cells Show Cross‐Resistance to UVA but not UVC Light

The isolation of photodynamic therapy (PDT)-resistant HT29 human colon adenocarcinoma cells has been reported previously. These PDT-resistant variants show increased expression of the Hsp27 and BNip3 proteins and a decreased expression of mutant p53 protein compared with parental HT29 cells. Because mutant p53 and increased expression of Hsp27 have been associated with resistance to various chemotherapeutic agents, whereas BNip3 is a potent inducer of apoptosis, we were interested in determining whether these PDT-resistant cells were cross-resistant to other cytotoxic agents. In the present report, we examined the colony survival of the PDT-resistant HT29 variants and several other clonal variants of HT29 cells to ultraviolet light (UV) treatment. The HT29 PDT-resistant variants showed cross-resistance to long-wavelength UVA (320-400 nm) but not to short-wavelength UVC (200-280 nm) light. Cell sensitivity to UVA or UVC was then correlated with Hsp27, BNip3 and mutant p53 protein levels in the PDT-resistant variants as well as in several clonal variants of HT29 cells that express different levels of Hsp27, BNip3 and mutant p53. We show that increased expression of Hsp27 and BNip3 and decreased expression of mutant p53 correlated with increased resistance to UVA. In contrast, increased expression of Hsp27 and BNip3 correlated with increased sensitivity to UVC, whereas increased expression of mutant p53 showed no significant correlation with sensitivity to UVC. These results suggest that the PDT-resistant HT29 cell variants are differentially sensitized to UVA compared with UVC due, in part at least, through the altered expression levels of BNip3, Hsp27 and mutant p53.

Use of Psoralen Plus UV-A Therapy in the Autonomous Community of Valencia, Spain

Background Photochemotherapy with 8-methoxypsoralen and long-wavelength UV-A (PUVA) has been extensively used for the treatment of various skin diseases since its approval in 1982 by the US Food and Drug Administration. Methods A retrospective study was performed of patients treated with PUVA, including topical and systemic treatment, over a period of 14 years. All patients were treated using a standard PUVA therapy regimen. Results A total of 877 patients were analyzed for the period 1982 to 1996. Forty-one skin diseases were treated, including 341 cases of psoriasis and 71 cutaneous T-cell lymphomas. The aim of the study was to describe the characteristics of the patients treated with PUVA therapy during that period and compare the results with those observed in other regions. Conclusions Although PUVA therapy is widely used in a large number of countries for the treatment of various skin diseases, few studies have described the characteristics of the patients and the differences in the parameters of PUVA according to the disease.

Validation Studies in European Blood Centers To Evaluate Processing Whole-Blood-Derived or Apheresis Plasma Using the INTERCEPT Blood System Intended for Commercialization.

Introduction: INTERCEPT plasma (I-FFP) for transfusion is prepared with a photochemical treatment (PCT) system using amotosalen (S-59) and long-wavelength UVA light to inactivate a broad spectrum of blood-borne pathogens. For Phase 3 clinical trials, 6 US blood centers prepared an inventory of ~10,000 I-FFP units by processing ~250 mL whole blood-derived (WB) or apheresis (APH) plasma units using a prototype PCT system. In these trials, I-FFP effectively supported patients with congenital and acquired coagulopathies or TTP. The prototype PCT system has been modified to treat up to 635 mL of plasma in a single PCT process, yielding up to three ~200 mL doses while maintaining pathogen inactivation efficacy. This modified PCT system intended for commercialization was evaluated in process validation studies in 3 European blood centers under routine operating conditions. After processing with the commercial PCT system, the effect on coagulation factor activity and retention was assessed in APH plasma (Blood 2004; 104:746a) and, as reported here, in WB plasma.Methods: Whole blood and/or APH plasma units were collected at 3 European blood centers. Three-unit pools (~600 mL) of WB plasma were prepared. APH plasma (~600 mL) was collected using Autopheresis C (Baxter) or MCS+(Haemonetics) devices. Blood bank personnel processed a total of 60 WB plasma pools and 90 APH plasma units using the commercial PCT system. Baseline and I-FFP plasma samples were collected, frozen below -60°C, and sent to Cerus for assay of factors I (fibrinogen), II, V, VII, VIII, IX, X, XI, and XIII, proteins C (PC) and S (PS), and antithrombin III (AT). Alpha-2 antiplasmin (AP) was assayed by a reference laboratory. Comparative data from a representative subset of I-FFP units prepared for the Phase 3 trials using the prototype PCT system were obtained from samples collected during PCT processing and stored at ≤−70°C. Retention of activity is expressed as the proportion (%) of pre-treatment (baseline) activity remaining after PCT.Results: Retention of coagulation factor activity in WB and APH I-FFP prepared with the commercial PCT system (Comm) was 73–76% of baseline fibrinogen and FVIII activity, and 80–97% of baseline for factors II, V, VII, IX, X, XI, XIII, PC, PS, AT, and AP (Table). Retention of activity in I-FFP prepared with the commercial PCT system was similar to that of I-FFP prepared with the clinical prototype.Conclusion: The PCT system intended for commercialization provides multiple I-FFP doses with a single PCT process. Retention of coagulation factor activity in WB and APH plasma processed with the commercial PCT system was similar to that of I-FFP used in Phase 3 trials to effectively support patients with congenital and acquired coagulopathies or TTP. [Display omitted]

Photosynthesis, photosynthetic pigments and mycosporine-like amino acids after exposure of the marine red alga Chondrus crispus (Gigartinales, Rhodophyta) to different light qualities

G. Kräbs and C. Wiencke. 2005. Photosynthesis, photosynthetic pigments and mycosporine-like amino acids after exposure of the marine red alga Chondrus crispus (Gigartinales, Rhodophyta) to different light qualities. Phycologia 44: 95–102.Low light–adapted laboratory-grown thalli of Chondrus crispus were transferred into shallow water and exposed to the natural irradiance prevailing in May–June at Helgoland (German Bight). A set of cut-off filters was used to study the wavelength-dependent response of photosynthesis as well as pigment and mycosporine-like amino acid (MAA) formation. Due to the higher natural irradiance and in some cases additional ultraviolet (UV) radiation, a depression of maximal quantum yield coinciding with a decline in maximal electron transport rate could be observed during the first days of the experiment. Faster recovery of maximal quantum yield and maximal electron transport rate might be related to the increase in lutein and α- and β-carotene concentration. In addition, higher rates of electron transport might be supported by increased chlorophyll a concentration. In parallel, MAA concentration increased resulting in an effective UV sunscreen. Our data suggest that lutein and α- and β-carotene are involved in the recovery of photochemical capacity, whereas MAAs provide a UV sunscreen, which may reduce the light available within the algae to long-wavelength UV-A and photosynthetically active radiation.

In vitro assessment of the broad-spectrum ultraviolet protection of sunscreen products

Background: There are considerable data to suggest that protection from solar ultraviolet (UV) radiation will reduce the risk of acute and chronic skin damage in humans. Whereas the sun protection factor (SPF) provides an index of protection against erythemally effective solar UV, largely confined to the UVB (290-320 nm) and short-wavelength UVA (320-340 nm) region, there is currently no agreed-upon method to measure broad-spectrum protection against long-wavelength UVA (340-400 nm). Objective: The objective of these studies was to assess the potential of in vitro UV substrate spectrophotometry and subsequent calculation of the “critical wavelength” value as a measure of broad-spectrum UV protection and as a routine, practical procedure for classification of sunscreen products. Methods: The spectral absorption of 59 commercially available sunscreen products and multiple experimental formulas with one or more UV filters was measured. Sunscreen product, 1 mg/cm2, was applied to a hydrated synthetic collagen substrate, preirradiated with a solar simulator, and then subjected to UV substrate spectrophotometry. Multiple determinations from 5 independent samples per product were used to calculate the critical wavelength value, defined as the wavelength at which the integral of the spectral absorbance curve reached 90% of the integral from 290 to 400 nm. Results: We found that a recognized long-wave UVA active ingredient such as titanium dioxide, zinc oxide, or avobenzone is a necessary but insufficient product requirement for achieving the highest proposed broad-spectrum classification, that is, critical wavelength of 370 nm or more. Although SPF and critical wavelength are largely independent of each other, UVA absorbance must increase commensurate with SPF to maintain the same critical wavelength value. Substrate spectrophotometry and the calculation of critical wavelength can readily account for sunscreen photostability by UV preirradiation. Finally, there is also a strong positive relationship between critical wavelength and a currently available in vivo measure of UVA protection. Conclusion: Determination of critical wavelength by means of UV substrate spectrophotometry provides a rapid, inexpensive, and reliable measure of broad-spectrum protection, which is largely independent of SPF, yet ensures long-wavelength UVA protection commensurate with SPF. The procedure provides a routine, sensitive means of differentiating and classifying sunscreen products and, importantly, obviates the need to subject volunteers to acute exposures of high-dose, nonterrestrial UV, the health risks of which are still poorly understood. (J Am Acad Dermatol 2000;43:1024-35.)