The effect of on-site application density on the UV protection efficacy of sunscreens.

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.

Inhibitory effect of the extract of rhizome of Curcuma longa L in gelatinase activity and its effect on human skin.

Exposure to UV radiation to human skin up-regulates the synthesis of matrix metalloproteinase (MMP) family. Gelatinases are member of MMPs which have been suggested to play an important role in photoaging such as wrinkle formation. To inhibit gelatinase activity is regarded to be very important to keep healthy skin and to protect wrinkle formation. On the other hand, anti-photoaging agents are expected to be derived from natural resources, especially plants. Plant extracts having gelatinase-inhibitory effect that might be used as safe anti-photoaging ingredient were widely screened. An extract of rhizomes of Curcuma longa L. showed inhibitory effect of gelatinase activity. Curcuminoids and slight amount of compound, 6,11-dihydroxy-3-(4-hydroxy-3-mthoxyphenethyl)-7-[(E)-4-(4-hydroxy-3-methoxyphenyl)-2-oxo-3-butenyl]-10-methoxy-2-oxabicyclo[6.3.1.]dodeca-1(11),8(12),9-trien-5-yl (E)-3-(4-hydroxy-3-methoxyphenyl)-2-propenoate (curcuminoid D) were isolated as the gelatinase-inhibitory components from methanol extract of rhizomes. The structure of curcuminoid D was determined by means of spectral data including 1H- and 13C-NMR, and IR. Curcumin exerted the enhancing effect on deposition of basement membrane component at dermal-epidermal junction in skin equivalent model. Topical application of cream containing turmeric extract significantly improved facial skin elasticity and decreased the number of gelatinase-positive stratum corneum clusters in human facial skins. These results indicated that turmeric is an effective ingredient to improve skin condition and to prevent skin from photoaging by suppressing activation of gelatinase chronically caused by UV.

Effect of oral intake of winged bean extract on a skin lichenification model: evaluation by microarray analysis.

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.