Winged bean (WB), Psophocarpus tetragonolobus, is a tropical legume, the potential of which is not fully understood. We found that 5-week oral administration of a WB seed extract inhibited wrinkle formation induced by repeated tape stripping (TS) as a model of lichenification in human chronic eczematous dermatitis. To elucidate the mechanism of the effect of WB on this model, we applied microarray analysis. Hierarchical clustering revealed that each experimental group formed a distinct cluster, suggesting the presence of a distinct gene expression profile among the three groups of non-TS, TS, and TS with oral administration of WB extract (TS/WB). Gene ontology analysis showed that several gene groups with keratinization and mitosis were significantly upregulated by TS, while other groups with ATP synthesis and glycolysis were significantly downregulated by TS/WB. Moreover, WB extract influenced a number of genes related to epidermal differentiation and inflammation. This suggests that these changes inhibited wrinkle formation by TS.
Background
Sun protection factor (SPF) and UVA protection factor (UVAPF) are performance indicators consumers recognize for UV protective cosmetics such as sunscreens. However, on‐site application density affects actual UV protection, despite these indicators. To understand actual UV protection better, a more reliable manner is needed to verify application density for further discussion of photoprotection efficacy regarding public health.
Objectives
To estimate the UV protective efficacy of sunscreen in actual use based on the application density of UV protective cosmetics and the analysis of UV protective effect modulated by application density.
Method
The subjects applied the SPF‐labeled sunscreens as usual. We measured the application amount and area including any amount on their hands to calculate the average application density on the face. Also, sunscreens were applied at densities of 0.5, 1.0, and 2.0 mg/cm2. The SPF values were measured at each application site to evaluate the effect of application density on photoprotection efficacy.
Result
We established a method of measuring application density utilizing three‐dimensional photograph analysis. The median application density of the sunscreen applied in actual use was 1.33 mg/cm2. The measured SPF values decreased in association with the decreased application density of sunscreens. Based on the estimate assuming the first‐order correlation, the SPF value required to get the protective effect equivalent to a sunscreen with SPF 15, 30, or 50 at 2 mg/cm2 was calculated to be 23.8, 47.5, and 79.2, respectively, with the application density of 1.33 mg/cm2.
Conclusion
We demonstrated a reasonable procedure for estimating the photoprotection efficacy of sunscreens on the face. A suggestion was made to consider the application density for further discussion of photoprotection among consumers, especially for the long term with respect to public health.
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