Photostabilization of Butyl methoxydibenzoylmethane (Avobenzone) and Ethylhexyl methoxycinnamate by Bis-ethylhexyloxyphenol methoxyphenyl triazine (Tinosorb S), a New UV Broadband Filter¶

Recent developments in tuning the efficacy of different types of sunscreens

Due to recent global warming threats, the changes in the atmosphere have caused significant ultraviolet (UV) radiation exposure, primarily emitted by the sun, which creates more awareness of photoprotection. Sunscreen development has been a convenient and crucial approach to photoprotection against ultraviolet radiation. Due to high demand, upgrading the quality of sunscreen products and certifying methods are necessary to guarantee the safety of commercial sunscreen products for use. Sunscreen products should have a satisfactory amount of sun protection factor (SPF), ultraviolet A protection factor, as well as the photostability of the sunscreens for them to be considered effective and safe for use. A rigorous study on the effectiveness of the sunscreen components and their safety standards is essential for the productive use and further improvement of the available sunscreen materials. This article summarizes the effects and issues, protective measures of sunscreen usage, and its components, mainly ultraviolet filters.

Peptide Cysteine Thiols Act as Photostabilizer of Avobenzone through Stabilising the Transition State of Keto-enol Tautomerization

Photostabilizers have been used to impart stability to an FDA-approved chemical UV-A filter avobenzone against the UV-A radiations and sunlight. The thiol group of glutathione plays a critical role in imparting the photostabilization activity of glutathione on avobenzone. The current report aims to evaluate the photostabilization activity of multiple thiols containing cysteine peptides on avobenzone. Cysteine-tripeptide and cysteine-pentapeptide were chemically synthesized and characterized using mass spectrometry. Synthetic peptides were assessed for their photostabilization activity on the enolic-form of the avobenzone under natural sunlight using UV-spectroscopy in both protic and aprotic solvents. Unlike glutathione which has pronounced activity in protic solvents, cysteine-pentapeptide exhibits similar photoprotection activity in both protic and aprotic solvents. Computational calculations using DFT suggest that peptide cysteine thiols may assist in the reversal of the photoketonization process of avobenzone thereby exhibiting the photoprotection activity to the enolic-form of avobenzone. Peptide cysteine thiols lower the activation energy barrier of keto-to-enol tautomerization of avobenzone by 30 kcal/mol by assisting the proton shuttle through a six-membered transition state. The current report emphasizes the applications of peptide thiols in cosmetics and may help in the development of peptides as aesthetic medicines.

Ultraviolet filters in sunscreens and cosmetic products-A market survey

BACKGROUND

As several reports have raised a variety of environmental, health, and safety issues related to ultraviolet (UV) filters, it is crucial to understand the trends in the exposure of the population to UV filters.

OBJECTIVE

To determine the frequency of UV filter usage in sunscreens and other cosmetic products in Thai market.

METHODS

We surveyed the UV filter labelling on sunscreens and cosmetic products sold in the Thai market. In all, 312 sunscreens and 1350 other cosmetic products were investigated.

RESULTS

Titanium dioxide was the most frequently used UV filter in both sunscreens (66.7%) and other cosmetic products (68.4%). Ethylhexyl methoxycinnamate was the most common organic UVB filter, whereas butyl methoxydibenzoylmethane was the most common organic UVA filter. In sunscreens aimed at children, bis-ethylhexyloxyphenol methoxyphenyl triazine was the most commonly used UV filter. The most frequent co-occurrence of UV filters was titanium dioxide and ethylhexyl methoxycinnamate.

CONCLUSIONS

Titanium dioxide was the most commonly used UV filter, which differs from the findings of previous surveys. Knowing the availability and frequency of each UV filter provides valuable information about consumer exposure levels, facilitates refinements of the allergen series in patch testing, and enhances the monitoring of adverse effects of UV filters.

Photopatch testing in a tropical country, Thailand: 20 years' experience

BACKGROUND

Photoallergic contact dermatitis is one of the important parts of photodermatoses. The investigation of choice is photopatch testing. However, reports with photopatch test results from Asian countries are scarce. The objective of this study was to determine the prevalence of positive photopatch test reactions and to ascertain the common photoallergens among Thai patients during 1998-2018.

METHODS

We retrospectively reviewed the records of 339 patients who were clinically suspected of having photoallergic contact dermatitis and had undergone photopatch testing.

RESULTS

A total of 44 photoallergic contact reactions in 38 patients (11.2%) were found. The positive photoallergic reactions were mainly found with organic ultraviolet filters and fragrances.

CONCLUSIONS

Organic ultraviolet filter chemicals especially benzophenone-3 and fragrances were found to have a high prevalence of photoallergic contact reactions. Monitoring of the photoallergens employed in photopatch tests should be conducted periodically to provide the best patient care.

Revisiting the Role of Irradiance in the Determination of Sunscreens' Sun Protection Factor

The efficacy of a sunscreen tends to be associated with its sun protection factor (SPF) value, a figure determined in a test that relies on the independence of the SPF value to both UV radiation dose and irradiance. We probe these assumptions when photoinduced product degradation is present, and we estimate that the theoretical limit for their validity is when the sunfilter active molecule relaxation time is faster than ∼10 ns. While such threshold relaxation time should be compatible with the expected ultrafast relaxation mechanisms of sunfilter molecules (picoseconds), recent research on sunfilter photodynamics has identified the existence of much longer-lived molecular states. Such long lifetimes could compromise sunscreen performance and make the SPF value very different in natural sun irradiance conditions than in the solar simulated conditions typically used in SPF determination tests.

Photoprotection assessment of olive (Olea europaea L.) leaves extract standardized to oleuropein: In vitro and in silico approach for improved sunscreens

Olive leaves contain higher amount of polyphenols than olive oil and represent a waste product from olive harvest and pruning of olive trees. The most abundant compound in olive leaves is oleuropein. Benefits of the topical application of olive leaves extract were previously reported, but little information is available on its photoprotective potential and the result of the association of this extract with organic UV filters in topical sunscreen formulations. The olive leaves extract photoprotective potential is less explored for both oral and topical photoprotection in comparison with other plants extracts and polyphenols, such as Polypodium leucotomos extract and resveratrol. There are increasing efforts towards developing more efficient sunscreens and a photoprotection assessement along with a better understanding of the photochemistry of naturally occurring sunscreens could aid the design of new and improved commercial sunscreen formulations. This study was designed to investigate the photoprotective potential of olive leaves extract standardized for oleuropein performing a set of in vitro and in silico tools as an innovative approach, highlighting yeast assays, in vitro Sun Protection Factor (SPF) and molecular modelling studies of UV absorption. This study supports the use of olive leaves extract for photoprotection, as an effective photoprotective, anti-mutagenic and antioxidant active, also showing a synergistic effect in association with UV filters with an improvement on in vitro SPF of sunscreen formulations.

Multifunctional Photostable Nanocomplex of ZnO Quantum Dots and Avobenzone via the Promotion of Enolate Tautomer

Ideal multifunctional ultraviolet radiation (UVR) absorbents with excellent photostability, high molar absorptivity, broadband UVR screening, and desired skin sensorial properties remain a significant challenge for the sunscreen industry. The potential of the nanocomplex (NCx) formed by microwave synthesis of ZnO quantum dots (QDs) in the presence of Avobenzone (Av) for achieving these goals is reported. The NCx exhibits unique synergy between ZnO QD and Av components, which enhances the photostability and molar absorptivity, extends UVA filtering range, and provides a visible emission that matches the typical human in vivo skin emission color. Density functional theory (DFT) and time-dependent DFT calculations of ZnO-Av hybrid structures and comparison of their spectroscopic features with experiments suggest that ZnO QDs catalyze the formation of highly photostable surface enolate species via aldol condensation reaction. The combination of experiments and computations used in this study can advance the science and technology of photoprotection.

Is there truly no benefit with sunscreen use and Basal cell carcinoma? A critical review of the literature and the application of new sunscreen labeling rules to real-world sunscreen practices

Basal cell carcinoma (BCC) is the most common human malignancy. Both epidemiological and direct evidence have established ultraviolet (UV) exposure from the sun as the most important risk factor for BCC development. There has only been one randomized and controlled study to examine sunscreen's role in the prevention of BCC, and no significant protective benefit was found. This study did not address four important concepts: sunscreen abuse, sunscreen misuse, sunscreen formulation, and cumulative UV exposure. Thus, the results of this study are difficult to interpret and extrapolate with real-world sunscreen practices.