A recent study published in Clinical, Cosmetic and Investigational Dermatology shows not only that UVA induces cyclobutane pyrimidine dimer (CPD) generation hours after exposure, but also how a chrysanthemum and ascorbic acid-2-glucoside (AA2G) blend can inhibit this production; potentially opening up a new category for post-sun exposure care.
As explained in the article, UV induces DNA damage in skin both directly, via the absorption of UVB, or indirectly by photosensitization mediated through UVA. Regarding the latter, the present work revealed that UVA specifically induces CPD generation via chemi-excitation in melanocytes even hours after exposure is suspended. These findings concur with previous literature suggesting sun light can damage skin hours after the exposure—via "dark" CPD formation.
Topical Solution and Testing
The Amway and Zen-Bio Inc. researchers also tested a blend of Chrysanthemum morifolium flower extract and a vitamin C derivative, AA2G, for its ability to protect against reactive oxygen species (ROS), melanin formation and UVA-induced dark CPD. Intracellular ROS levels were measured in epidermal keratinocytes using a specified dye, and melanogenesis inhibition efficacy was determined using B16 cells.
Pre-treatment with the test blend imparted preventive effects on dark CPD formation.
As for the dark CPD measurement, briefly, Melan-a cells were treated with or without the test actives for six days, then irradiated with UVA at various doses. Cells were exposed with an anti-CPD antibody and a secondary antibody. CPD levels were then determined by measuring fluorescence intensity using a imaging analysis.
Results showed the blend of both the chrysanthemum extract and AA2G demonstrated ROS-scavenging and anti-melanogenesis effects better than they did individually. In addition, pre-treatment with the test blend imparted preventive effects on dark CPD formation.
Post-exposure Care Extends Protection
The researchers concluded while consumers believe solar protection is needed only during the daytime, this work establishes how DNA damage can occur hours after exposure to the sun; specifically UVA. In response, the natural antioxidant Chrysanthemum morifolium flower extract, in combination with the well-known vitamin C derivative AA2G, enhances skin protection against delayed DNA damage; aka dark CPD formation. Such combination strategies could be used to formulate post-exposure products to alleviate skin damage after solar exposure.