Can natural products improve skin photoprotection?

Abstract Due to increased UV radiation on the Earth’s surface, caused by depletion of the stratospheric ozone, people have become more susceptible to different types of skin damage, such as erythema, sunburns, and cancer; this is especially of concern in tropical countries. Thus, efforts to improve awareness as well as the use of sunscreen are increasing worldwide. However, synthetic UV filters have been associated with deleterious effects such as photosensitization. Natural products have been used by ancient cultures for several purposes, including protecting the skin from the sun. However, there is still doubt today whether photoprotection is a real phenomenom or whether it is simply tanning of the skin. Plants have self-protective mechanisms and produce secondary metabolites that can protect themselves from UV radiation. Yet, can phytochemical compounds protect human skin? This review discusses the paradoxical effect of chemical UV filters and the influence of phytochemicals in in vitro and in vivo tests of photoprotection.

摘要：由于平流层臭氧（stratospheric ozone）耗竭导致地球表面紫外线辐射（UV radiation）增强，人类罹患各类皮肤损伤的风险显著升高，包括红斑（erythema）、晒伤（sunburns）乃至皮肤癌；这一问题在热带国家尤为受到关注。因此，全球范围内提升防晒认知与推广防晒产品使用的相关举措正不断增多。然而，合成紫外线过滤剂（synthetic UV filters）已被证实存在光敏反应（photosensitization）等有害影响。古代文明早已将天然产物用于多种用途，其中便包括皮肤防晒防护。但时至今日，学界仍存在争议：光防护（photoprotection）究竟是真实存在的生理效应，抑或仅仅是皮肤晒黑的表象？植物自身具备防护机制，可合成能够抵御紫外线辐射的次生代谢产物（secondary metabolites）。那么，植物化学物（phytochemicals）能否对人类皮肤起到防护作用？本综述探讨了化学紫外线过滤剂的矛盾效应，以及植物化学物在光防护体外实验（in vitro）与体内实验（in vivo）中的影响。