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Photoallergy
Published in Henry W. Lim, Nicholas A. Soter, Clinical Photomedicine, 2018
Butyl methoxydibenzoylmethane (avobenzone, PARSOL 1789) is a new addition to sunscreens marketed in the United States. It is an excellent UVA absorber and is being marketed for this activity in “broad-spectrum” sunscreens. It has been reported to cause photoallergic contact dermatitis in Europe and will likely do the same in the United States.
Sunscreens
Published in Dimitris Rigopoulos, Alexander C. Katoulis, Hyperpigmentation, 2017
The major adverse effects of sunscreens are minor skin irritation, which is common, and allergic contact dermatitis, which is rare. These reactions are usually attributed to ingredients in the base of the product, such as fragrance or preservatives. Presently, the organic compounds most often responsible for the rare instances of allergy or photoallergy are oxybenzone and padimate O, and, less commonly, avobenzone.
Safety and Efficacy of Sunscreen Formulations Containing Carrier or Non-Carrier-Based UV-Filters
Published in Andreia Ascenso, Sandra Simões, Helena Ribeiro, Carrier-Mediated Dermal Delivery, 2017
Carolina Gomes Benevenuto, Lorena Rigo Gaspar
Avobenzone is the main representative of the dibenzoylmethanes due to its UVA absorption, with a lmax at 357 nm [51]. Although avobenzone has an appropriate UVA absorption spectrum and consequently is found in several photoprotective cosmetic formulations, this molecule may present photoreactivity when exposed to UV [52–55]. This photoreactivity occurs due to the fact that avobenzone undergoes keto-enol tautomerization (AVOK-AVOE). In a sunscreen formulation, avobenzone exists predominantly in the enol form, which absorbs in the UVA range. The relative amounts of the two isomers are solvent dependent but the equilibrium always lies in the direction of the enol tautomer, which will consequently impart high sunscreen efficiency. However, under UV radiation, the keto-enol equilibrium is shifted toward the keto form of avobenzone, which absorbs in the UVC range from 260 to 280 nm and can lead to the majority of the harmful effects of avobenzone, such as its irreversible photodegradation and ROS formation [51,56].
Insights and controversies on sunscreen safety
Published in Critical Reviews in Toxicology, 2020
Juliana P. Paiva, Raiane R. Diniz, Alvaro C. Leitão, Lucio M. Cabral, Rodrigo S. Fortunato, Bianca A. M. C. Santos, Marcelo de Pádula
Although organic UV filters are intended to absorb sunlight, protecting skin from sunburn and cancers, some of them are not photostable (Hanson et al. 2015; Stein et al. 2017). Upon UV exposure, some molecules are degraded forming photoproducts, which results in a reduction of sunscreen effectiveness. Furthermore, these photoproducts can be potentially toxic to organisms (Butt and Christensen 2000; Klimova et al. 2013). One commonly used organic UV filter that degrades rapidly upon UV exposure forming several photoproducts is OMC. Stein et al. (2017) isolated and characterized the major products of OMC photolysis concluding that 4-methoxybenzaldehyde and the two OMC dimerization cyclodimers forms (δ-truxinate and α-truxillate) are significantly toxic to mammalian cells (Stein et al. 2017). 2-Ethylhexanol, another OMC photoproduct, also shows toxic effect to zebrafish (Nataraj et al. 2020). Furthermore, the degradation of an UV filter also may be induced by photocatalytic activity of others filters, such as degradation of 2-phenylbenzimidazole-5-sulfonic acid (PBSA) filter by TiO2 photocatalysis (Ji et al. 2013). The widest UVA attenuation is achieved with avobenzone (AVB), but this substance tends to be highly photolabile generating benzyls and arylglyoxals after UV exposure. In addition, arylglyoxal in contact with the skin is a strong sensitizer generating photocontact allergy (Karlsson et al. 2009; Paris et al. 2009).
An RNAi-mediated screen identifies novel targets for next-generation antiepileptic drugs based on increased expression of the homeostatic regulator pumilio
Published in Journal of Neurogenetics, 2018
Wei-Hsiang Lin, Miaomiao He, Yuen Ngan Fan, Richard A. Baines
We have recently reported a luciferase-based reporter of dPum activity and screened an FDA-approved drug library to identify compounds that promote the activity of this homeostatic regulator (Lin, et al., 2017). This screen identified, amongst other compounds, avobenzone. Our follow-on studies indicate this compound promotes transcription of dpum and increased dPum protein. Moreover, this compound has potent anticonvulsive properties when fed to bs mutant Drosophila. In this present study, we expand our screening to incorporate a genome-wide RNAi library. We identify 699 RNAi’s that are sufficient to potentiate dPum activity. A comparison of these 699 genes with activity-dependent genes, identified through an RNA-sequencing approach (Lin, et al., 2017), shows that 101 genes are also regulated by synaptic activity. The protein products of these 101 genes may prove to be favourable targets for drug-mediated inhibition to better control epilepsy. To show proof-of-principle, we express RNAi targeted to these genes in the parabss seizure mutant background and report that 57 significantly reduce seizure duration. We validate, where possible, anticonvulsant effects through feeding of chemical inhibitors for the respective gene protein products.
Prospects of topical protection from ultraviolet radiation exposure: a critical review on the juxtaposition of the benefits and risks involved with the use of chemoprotective agents
Published in Journal of Dermatological Treatment, 2018
Nilutpal Sharma Bora, Bhaskar Mazumder, Pronobesh Chattopadhyay
Benzophenones possess good broad-spectrum UVB and UVA protection range. They are intensely photolabile and can undergo oxidation which can interfere with the antioxidant system. Out of the three FDA-approved benzophenones; namely oxybenzone, sulisobenzone, and dioxybenzone, oxybenzone is most commonly used, but also has the highest incidence of photoallergic contact dermatitis (64). Meradimate is another benzophenone which used in conjugation with other agents to enhance UVA protection (67). Avobenzone (butyl methoxydibenzoylmethane) is a potent UVA filter and was the first FDA approved organic agent which is able to effectively filter UVA (340–400 nm). However, avobenzone is highly photolabile; and loses 50–60% of its potency within 1 h of sun exposure (68,69). Avobenzone also affects the stability of other active sunscreen ingredients, like octocrylene and bemotrizinol and much research has been done to stabilize formulations containg these ingredients (70–72).