Abstract
Polyphenols are a large family of natural compounds widely used in cosmetic products due to their antioxidant and anti-inflammatory beneficial properties and their ability to prevent UV radiation-induced oxidative stress. Since these compounds present chromophores and are applied directly to the skin, they can react with sunlight and exert phototoxic effects. The available scientific information on the phototoxic potential of these natural compounds is scarce, and thus the aim of this study was to evaluate the photoreactivity and phototoxicity of five phenolic antioxidants with documented use in cosmetic products. A standard ROS assay was validated and applied to screen the photoreactivity of the natural phenolic antioxidants caffeic acid, ferulic acid, p-coumaric acid, 3,4-dihydroxyphenylacetic acid (DOPAC), and rutin. The phototoxicity potential was determined by using a human keratinocyte cell line (HaCaT), based on the 3T3 Neutral Red Uptake phototoxicity test. Although all studied phenolic antioxidants absorbed UV/Vis radiation in the range of 290 to 700 nm, only DOPAC was able to generate singlet oxygen. The generation of reactive oxygen species is an early-stage chemical reaction as part of the phototoxicity mechanism. Yet, none of the studied compounds decreased the viability of keratinocytes after irradiation, leading to the conclusion that they do not have phototoxic potential. The data obtained with this work suggests that these compounds are safe when incorporated in cosmetic products.
Highlights
Polyphenols (PPs) constitute one of the most numerous and widely distributed groups of natural products in the plant kingdom
Phototoxicity assay (3T3 NRU-PT) were used to examine the behavior of natural phenolic antioxidants when exposed to radiation mimicking the sunlight in order to examine their photoreactivity and phototoxicity potential
The data found suggest that these antioxidants by themselves are not expected to cause phototoxicity and they can be considered safe for use in cosmetic formulations
Summary
Polyphenols (PPs) constitute one of the most numerous and widely distributed groups of natural products in the plant kingdom. Polyphenols may protect cell constituents against oxidative damaging effects of reactive oxygen species (ROS), such as singlet oxygen, superoxide, and hydroxyl radicals, limiting the risk of several diseases associated with oxidative stress [6,7]. Due to their chemical properties, PPs are able to scavenge ROS and chelate transition metals ions, such as iron and copper, which has attracted the interest of the cosmetic industry for their use in skin care formulations [8,9,10].
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