Photoprotection and Skin Pigmentation: Melanin-Related Molecules and Some Other New Agents Obtained from Natural Sources

Abstract

Direct sun exposure is one of the most aggressive factors for human skin. Sun radiation contains a range of the electromagnetic spectrum including UV light. In addition to the stratospheric ozone layer filtering the most harmful UVC, human skin contains a photoprotective pigment called melanin to protect from UVB, UVA, and blue visible light. This pigment is a redox UV-absorbing agent and functions as a shield to prevent direct UV action on the DNA of epidermal cells. In addition, melanin indirectly scavenges reactive oxygenated species (ROS) formed during the UV-inducing oxidative stress on the skin. The amounts of melanin in the skin depend on the phototype. In most phenotypes, endogenous melanin is not enough for full protection, especially in the summertime. Thus, photoprotective molecules should be added to commercial sunscreens. These molecules should show UV-absorbing capacity to complement the intrinsic photoprotection of the cutaneous natural pigment. This review deals with (a) the use of exogenous melanin or melanin-related compounds to mimic endogenous melanin and (b) the use of a number of natural compounds from plants and marine organisms that can act as UV filters and ROS scavengers. These agents have antioxidant properties, but this feature usually is associated to skin-lightening action. In contrast, good photoprotectors would be able to enhance natural cutaneous pigmentation. This review examines flavonoids, one of the main groups of these agents, as well as new promising compounds with other chemical structures recently obtained from marine organisms.

Unraveling the roles of vitamin D status and melanin during Covid‑19 (Review)

“…Apart from defining an important phenotypic trait, melanin appears to play a major role in the natural photoprotection of skin ( 42 , 43 ). In evolution, skin pigmentation in the human lineage has developed via a process of natural selection primarily to protect the skin from the damaging effects of solar UV radiation (UVR) ( 44 ).…”

“…In evolution, skin pigmentation in the human lineage has developed via a process of natural selection primarily to protect the skin from the damaging effects of solar UV radiation (UVR) ( 44 ). Since UVR can exert cytotoxic, mutagenic and immunosuppressive effects, either by direct action on DNA or indirectly by generating reactive oxygen species (ROS) and oxidative stress, the epidermis has been armed with melanin to maintain and/or restore local homeostasis against the UVR-driven insults ( 37 , 42 , 43 , 45 ). Melanosomes, by forming supranuclear caps, protect keratinocytes from solar UV-induced DNA damage, while eumelanin acts as a direct scavenger of ROS generated upon UV exposure, reducing oxidative cellular damage ( 34 , 42 , 43 ).…”

Adaptation and co‐adaptation of skin pigmentation and vitamin D genes in native Americans

“…The cutaneous production of vitamin D is linked with radiation exposure. Thus, vitamin D production is also dependent on the level of pigmentation since it determines the skin's ability to block the penetration of ambient radiation (D'Orazio et al, 2013; Jablonski, 2004; Solano, 2020). People with darker skin produce less vitamin D than people with fair skin (Engelsen, 2010; Juzeniene et al, 2009; Khalid et al, 2017; Young et al, 2020).…”

Administration of Apple Polyphenol Supplements for Skin Conditions in Healthy Women: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

“…However, these enzymes are unable to completely scavenge and remove the ROSs and free radicals [11]. Therefore, prevention and protection from UV-mediated cellular damage may be useful for preventing skin disorders.To neutralize these ROSs, phytochemicals including polyphenols, carotenoids, and antioxidants in foods are required [6,12]. Dietary supplementation with vitamins, carotenoids, and phytochemicals such as polyphenols are proposed to improve skin conditions.…”

“…To neutralize these ROSs, phytochemicals including polyphenols, carotenoids, and antioxidants in foods are required [6,12]. Dietary supplementation with vitamins, carotenoids, and phytochemicals such as polyphenols are proposed to improve skin conditions.…”