Performance Metrics of Sunscreen Formulations: In Vitro and In Vivo Techniques.

Effective skin protection of consumers by sunscreens can only be achieved when meaningful and reliable test methods are available to objectively measure the protection of sunscreen products. Quantitative, scientifically sound, and valid methods to detect UVB and UVA light protection as well as methods to assess sunscreen substantivity to water are required. Continuous improvement and, if necessary, extension of the test methods are important to provide optimum protection from harmful sun rays to the consumer. This work documents the historical background of the development of sunscreen test methods and provides the actual worldwide status of applied methods. Future developments and trends are discussed as far as they actually become apparent.

Assessment of Natural Sunlight Protection Provided by 10 High-SPF Broad-Spectrum Sunscreens and Sun-Protective Fabrics.

In 1978, the FDA Advisory Panel proposed both indoor and natural sunlight SPF testing methods but reverted to indoor testing only in 1993. Today's sunscreen sun protection and broad-spectrum claims are based on mandated clinical tests using solar simulators and in vitro spectrophotometers. This research evaluated the protection of 10 high-SPF (30-110), broad-spectrum sunscreen products, as well as 6 sun-protective fabrics against natural sunlight in Arequipa, Peru. Each of the 17 subjects was exposed to natural sunlight for 1 h and 59 min under clear skies, with temperatures and humidity similar to those in an indoor clinical laboratory. Test sites were photographed 16-24 h later. Four dermatologists evaluated the photographs for erythema and persistent pigment darkening (PPD). Perceptible sun-induced skin injury (sunburn and/or pigmentation) was detected at 97% of the sunscreen-protected scores. The most sun-sensitive subjects obtained the least erythema protection. The higher the SPF was, the higher the erythema protection, but the intensity of PPD was also higher. The 2 sunscreens using only FDA-approved sunscreen filters rated 30 SPF and 45+ SPF performed poorly: Eighty-one percent of the 136 scores were graded 1 minimal erythema dose or higher erythema, achieving, at a maximum, SPF of 5-7 in natural sunlight. Sun-protective fabrics tested provided excellent sun protection. The erythema and PPD observed through the sunscreens in less than 2 h are incongruous with the broad-spectrum, high-SPF sunscreen claims. Reapplying these sunscreens and staying in the sun longer, as stated on the product labels, would have subjected the subjects to even more UV exposure. High-SPF, broad-spectrum sunscreen claims based on indoor solar simulator testing do not agree with the natural sunlight protection test results.

Sunscreens in the United States: Current Status and Future Outlook.

Incidence rates of nonmelanoma skin cancer and melanoma have been on the rise in the USA for the past 25 years. UV radiation (UVR) exposure remains the most preventable environmental risk factor for these cancers. Aside from sun avoidance, sunscreens continue to provide the best alternative protection. UVR directly damages DNA and causes indirect cellular damage through the creation of reactive oxygen species, the sum of which leads to cutaneous immunosuppression and a tumorigenic milieu. The current generation of sunscreens protect from UVR through two main mechanisms: absorption and deflection. In the USA, the Food and Drug Association (FDA) regulates sunscreen products which are considered over-the-counter drugs. With the release of new FDA testing and labeling requirements in 2011 and the enactment of the Sunscreen Innovation Act in 2014, sunscreen manufacturers are now required to evaluate their products not only on the sun protection factor (SPF) but also on broad-spectrum UVA protection. The American Academy of Dermatology Association and the American Academy of Pediatrics have provided specific recommendations for proper sun protection and sunscreen usage with the continual goal of increasing public awareness and compliance with appropriate sun protective measures. Antioxidants, photolyases, and plant polyphenols remain an interesting avenue of research as additives to sunscreens or stand-alone topical or oral products that appear to modulate the immunosuppressive effects of UVR on the skin. Additionally, although UVR induces endogenous cutaneous production of vitamin D, its damaging effects overshadow this positive benefit, especially in light of the ease of achieving recommended amounts of vitamin D through diet and supplementation.

Evaluation of Ubtan - A traditional indian skin care formulation.

ETHNOPHARMACOLOGICAL RELEVANCE: 'Ubtan' is a traditional herbal formulation in the Indian system of medicine being used in India and its subcontinent for a long time. Several commercial skin care formulations are marketed throughout this region as the name of Ubtan. Therefore, it is worthwhile to evaluate Ubtan in respect of its efficacy as skin care formulation. AIM OF THE STUDY: The present study was designed for the preparation of Ubtan and standardization through the chromatographic techniques by using suitable phyto-markers. Further, its antioxidant, sun protection factor (SPF) and anti-tyrosinase potential have been explored. MATERIALS AND METHODS: Four in-house formulations (UF-1, UF-2, UF-3 and UF-4) were prepared by mixing a varied quantity of each powdered plants, i.e. turmeric (Curcuma longa L.), Chickpea (Cicer arietinum L.) and sandalwood (Santalum album L.). Optimization of the formulations was made by evaluating its biological activity through in vitro assay. Evaluation of physicochemical properties of the optimized formulation (UF-1) has been carried out by analysis of pH, flow properties and stability. Moreover, RP-HPLC (reverse phase - high performance liquid chromatography) and HPTLC (high performance thin layer chromatography) standardization of UF-1 was performed for its quantitative and qualitative analysis. RESULTS: Ubtan formulations (UF-1to UF-4) showed free radical scavenging and ferric reducing potential. It may be due to its high phenolic and flavonoid content. Statistically, significant Pearson's correlation (r) was confirmed the positive correlation between phenolic content and SPF of the formulations. The tyrosinase inhibition study indicated that the formulations showed both diphenolase and monophenolase inhibitory activity. Among four formulations, UF-1 showed notable biological activity (p<0.05). The content of curcumin and ascorbic acid was found to be 1.6% and 2.1% w/w respectively in UF-1 through RP-HPLC estimation. Physiochemical properties of the UF-1 exhibited good flow rate and aqueous solubility. From the stability studies, it can be anticipated that the UF-1 was stable at 40°C for longer periods. Microbial load count and heavy metal content (lead-Pb, arsenic-As, mercury-Hg and cadmium-Cd) of the formulation was also within the permissible limit of a pharmacopeial standard. CONCLUSION: This scientific exploration helps to set the quality and safety standard of traditional cosmetic formulation, Ubtan and its further use as an herbal skin care product.

In vitro and in vivo photoprotective/photochemopreventive potential of Garcinia brasiliensis epicarp extract.

The damaging effects of sunlight to the skin has triggered studies that involve the synthesis and extraction of organic compounds from natural sources that can absorb UV radiation, and studies on polyphenolic compounds with antioxidant and anti-inflammatory properties that can be used as photochemopreventive agents for reducing skin damage. We investigated the in vitro and in vivo photoprotective/photochemopreventive potential of Garcinia brasiliensis epicarp extract (GbEE). We evaluated the cell viability of L929 fibroblasts after UVB exposure using a quartz plate containing the extract solution or the GbEE formulation. The in vivo photoprotective effect of the GbEE formulation was evaluated by measuring the UVB damage-induced decrease in endogenous reduced glutathione (GSH), the increase in myeloperoxidase (MPO) activity and secretion of cytokines IL-1ß and TNF-α. The in vitro methodology using fibroblasts showed that the photoprotective properties of the GbEE solutions and 10% GbEE formulation were similar to the commercial sunscreen (SPF-15). In vivo results demonstrated of the GbEE formulation in decreasing UVB induced-damage such as GSH depletion, an increased in MPO activity and secretion of cytokines IL-1ß and TNF-α. The results showed that the extract has great potential for use as a sunscreen in topical formulations in addition to UV filters.

Addressing technical challenges associated with the FDA's proposed rules for the UVA in vitro testing procedure.

The proposed rules of the Food and Drug Administration (FDA) for the UVA in vitro testing procedure were applied to the evaluation of various sunscreen formulations and the following technical challenges were observed: when proposed roughened quartz substrates were used, the required coefficient-of-variation criteria were not met, and the dynamic ranges of the available transmittance analyzers were exceeded for sunscreens with high SPF values. In the proposed rules, the FDA requested comment regarding the suitability of other possible substrates. In this research, two modifications to the FDA's proposed rules were evaluated: (a) the use of an alternative substrate, Vitro Skin N-19 (IMS, Inc.) instead of roughened quartz substrate and (b) an increase in application time from 10 seconds to 30 seconds to ensure a uniform distribution of sunscreen product over the application area of the substrate. These two modifications allowed meeting the required coefficient-of-variation criteria without exceeding the dynamic ranges of the available transmittance analyzers. The modified test conditions were utilized for the evaluation of six commercial sunscreens, which fulfilled criteria of "medium" or "high" categories-based on their UVAI/UV ratios. These findings were in agreement with the statement in the proposed rules that the FDA is aware of the difficulty for current sunscreen formulations to meet the "highest" category and believes that allowing such a category will foster additional research and development in this area. To determine if it was possible to achieve a UVA rating greater than 0.95, two experimental sunscreen prototypes with bisoctrizole (USAN), bemotrizinol (USAN), avobenzone, and octocrylene were tested under the modified test conditions and attained the "highest" category. It should be noted that bisoctrizole and bemotrizinol are being evaluated by the FDA under TEA and are not permitted in the US at this time, but they are approved for use in the rest of the world.

Development of a whole-organism model to screen new compounds for sun protection.

We used zebrafish as a whole-organism model to screen new compounds for sun protection activity. First of all, we designed a series of UVB exposure experiments and recorded the phenotypic changes of zebrafish embryos. Results showed that 100 mJ/cm(2) of UVB given six times separated by 30 min intervals is the best condition. Fin malformation (reduced and/or absent fin) phenotypes are the most evident consequences after exposure to UVB. Each fin was affected by UVB, including pelvic, ventral, caudal, and dorsal fin, but pelvic fin seemed to be the most sensitive target after UVB exposure. We furthermore carried out "prevention" and "treatment" experiments using green tea extract and/or (-)-epigallocatechin (EGCG) to test this whole-organism model by observing the morphological changes of all fins (especially pelvic fin) after UVB exposure. Effects of UVB, green tea extract and EGCG on fin development were assessed using the Kaplan-Meier analysis, log-rank test and Cox proportional hazards regression. Results showed that a zebrafish pelvic fin in the UVB + green tea (treatment) group is 5.51 (range from 2.39 to 14.90) times, one in the UVB + green tea (prevention) group is 7.04 (range from 3.11 to 18.92) times, and one in the 25 ppm of EGCG (prevention) group is 22.19 (range from 9.40 to 61.50) times more likely to return to normal fin than one in the UVB only group. On the basis of these observations, we believe this model is effective for screening the higher stability and lower toxicity of new compounds, such as small chemicals which are derivative from EGCG or other dietary agents for sun protection.

Sunscreens - which and what for?

It is well established that sun exposure is the main cause for the development of skin cancer. Chronic continuous UV radiation is believed to induce malignant melanoma, whereas intermittent high-dose UV exposure contributes to the occurrence of actinic keratosis as precursor lesions of squamous cell carcinoma as well as basal cell carcinoma. Not only photocarcinogenesis but also the mechanisms of photoaging have recently become apparent. In this respect the use of sunscreens seemed to prove to be more and more important and popular within the last decades. However, there is still inconsistency about the usefulness of sunscreens. Several studies show that inadequate use and incomplete UV spectrum efficacy may compromise protection more than previously expected. The sunscreen market is crowded by numerous products. Inorganic sunscreens such as zinc oxide and titanium oxide have a wide spectral range of activity compared to most of the organic sunscreen products. It is not uncommon for organic sunscreens to cause photocontact allergy, but their cosmetic acceptability is still superior to the one given by inorganic sunscreens. Recently, modern galenic approaches such as micronization and encapsulation allow the development of high-quality inorganic sunscreens. The potential systemic toxicity of organic sunscreens has lately primarily been discussed controversially in public, and several studies show contradictory results. Although a matter of debate, at present the sun protection factor (SPF) is the most reliable information for the consumer as a measure of sunscreen filter efficacy. In this context additional tests have been introduced for the evaluation of not only the protective effect against erythema but also protection against UV-induced immunological and mutational effects. Recently, combinations of UV filters with agents active in DNA repair have been introduced in order to improve photoprotection. This article reviews the efficacy of sunscreens in the prevention of epithelial and nonepithelial skin cancer, the effect on immunosuppression and the value of the SPF as well as new developments on the sunscreen market.

Prevention of ultraviolet radiation-induced suppression of contact and delayed hypersensitivity by Aloe barbadensis gel extract.

We investigated the ability of Aloe barbadensis gel extract to prevent suppression of contact hypersensitivity (CHS) and delayed-type hypersensitivity (DTH) responses in mice by ultraviolet (UV) irradiation. Local immune suppression was induced in C3H mice by exposure to four daily doses of 400 J/m2 UV-B (280-320 nm) radiation from FS40 sunlamps, followed by sensitization with 0.5% fluorescein isothiocyanate (FITC) through the irradiated skin. Topical application of 0.167-1.67% Aloe gel after each irradiation significantly reduced this suppression. Aloe treatment partially preserved the number and morphology of Langerhans and Thy-1+ dendritic epidermal cells in skin, compared to those in the skin of mice given only UVR or UVR plus the vehicle. Experiments using a single (2 kJ/m2) dose of UVR followed by Aloe treatment showed that the effect of Aloe was not due to screening of the UVR. Systemic suppression of DTH to Candida albicans or CHS to FITC was induced in C3H mice exposed to 5 or 10 kJ/m2 UV-B radiation, respectively, on shaved dorsal skin and sensitized 3 d later with a subcutaneous injection of formalin-fixed Candida or FITC painted on unirradiated, ventral skin. Treatment of the UV-irradiated skin with Aloe immediately after irradiation prevented suppression of both DTH to Candida and CHS to FITC. Aloe treatment did not prevent the formation of cyclobutyl pyrimidine dimers in the DNA of UV-irradiated skin or accelerate the repair of these lesions. These studies demonstrate that topical application of Aloe barbadensis gel extract to the skin of UV-irradiated mice ameliorates UV-induced immune suppression by a mechanism that does not involve DNA damage or repair.

Spectral comparison of solar simulators and sunlight.

In evaluating sunscreen efficacy, spectral distribution of the irradiation sources can influence the sun protection factor (SPF). The purpose of this investigation was to examine the uniformity of ultraviolet (UV) spectral irradiance of solar simulators used in various SPF testing laboratories, compare them with natural sunlight UV radiation (UVR), and recommend performance limits to ensure that the variability of radiation sources in the UVB region minimally affects SPF estimates. The critical portion of the solar erythemogenic spectrum was identified as the UVB portion, defined as the region between 280 and 320 nm. The spectral irradiance of 26 solar simulators and other UV sources was measured and compared with a summer noon solar spectrum measured in Albuquerque, NM. Proposed spectral limits were developed as a 6-nm "acceptance band" centered on this standard spectrum normalized at 320 nm. The results indicated that the xenon-arc solar simulators currently used in the United States in testing sunscreens either meet the proposed standard solar spectrum or can be readily modified with available UV filters to meet this standard. The devices that have spectral characteristics not resembling sunlight fail to meet the proposed standard and should not be used for sunscreen SPF testing.

Sunscreen testing using the mouse ear model.

During the developmental stages of sunscreen formulation it is desirable to have a simple, accurate and inexpensive biological model to test product effectiveness. Another desirable attribute is a quantitative, unbiased response endpoint for evaluation. We have developed such a test system based upon the ear swelling response of hairless albino mice. With this system, irradiation times are greatly reduced; furthermore, the response parameter is metric and can be determined noninvasively with an inexpensive micrometer. Protection factors determined with the mouse ear model show high correlation with the sun protection factors as determined on human subjects (r = 0.92) and were linearly related over a wide range of values. This new method affords a simple, accurate and inexpensive system for evaluation of efficacy and safety of new products.