Licochalcone A (LicA), a major phenolic constituent of the licorice species Glycyrrhiza inflata, has recently been reported to have anti-inflammatory as well as anti-microbial effects. These anti-inflammatory properties might be exploited for topical applications of LicA. We conducted prospective randomized vehicle-controlled clinical trials to assess the anti-irritative efficacy of cosmetic formulations containing LicA in a post-shaving skin irritation model and on UV-induced erythema formation. The clinical trials were accompanied by a series of in vitro experiments to characterize anti-inflammatory properties of LicA on several dermatologically relevant cell types. Topical LicA causes a highly significant reduction in erythema relative to the vehicle control in both the shave- and UV-induced erythema tests, demonstrating the anti-irritative properties of LicA. Furthermore, LicA is a potent inhibitor of pro-inflammatory in vitro responses, including N-formyl-MET-LEU-PHE (fMLP)- or zymosan-induced oxidative burst of granulocytes, UVB-induced PGE(2) release by keratinocytes, lipopolysaccharide (LPS)-induced PGE(2) release by adult dermal fibroblasts, fMLP-induced LTB(4) release by granulocytes, and LPS-induced IL-6/TNF-alpha secretion by monocyte-derived dendritic cells. The reported data suggest therapeutic skin care benefits from LicA when applied to sensitive or irritated skin.

It is often debated that the protection against solar-induced erythema under real conditions is dependent upon the amount of sunscreen applied. It is believed that when too little is applied a lower sun protection than indicated on the label will result. The aim of this study was to quantify this effect. In this multicenter study, the influence of three different amounts (0.5, 1.0, 2.0 mg/cm²) of three commercial sunscreen products in three reliable test centers was investigated according to the test protocol of The International Sun Protection Factor Test Method. The main result was a linear dependence of the SPF on the quantity applied. Taking into consideration the volunteer-specific variations, an exponential dependence of confidence interval of the in vivo SPF and amount applied was found. The highest amount applied (2.0 mg/cm²) was linked to the lowest confidence intervals. Thus, from the point of view of producing reliable and reproducible in vivo results under laboratory conditions, the recommendation of this multicenter study is an application quantity of 2.0 mg/cm².

Biochemical and structural changes of the dermal connective tissue substantially contribute to the phenotype of aging skin. To study connective tissue metabolism with respect to ultraviolet (UV) exposure, we performed an in vitro (human dermal fibroblasts) and an in vivo complementary DNA array study in combination with protein analysis in young and old volunteers. Several genes of the collagen metabolism such as Collagen I, III and VI as well as heat shock protein 47 and matrix metalloproteinase-1 are expressed differentially, indicating UV-mediated effects on collagen expression, processing and degradation. In particular, Collagen I is time and age dependently reduced after a single UV exposure in human skin in vivo. Moreover, older subjects display a lower baseline level and a shorter UV-mediated increase in hyaluronan (HA) levels. To counteract these age-dependent changes, cultured fibroblasts were treated with a specific soy extract. This treatment resulted in increased collagen and HA synthesis. In a placebo-controlled in vivo study, topical application of an isoflavone-containing emulsion significantly enhanced the number of dermal papillae per area after 2 weeks. Because the flattening of the dermal-epidermal junction is the most reproducible structural change in aged skin, this soy extract appears to rejuvenate the structure of mature skin.

Biochemical and structural changes of dermal connective tissue substantially contribute to the phenotype of aging skin. To study connective tissue metabolism with respect to ultraviolet (UV) exposure, we performed an in vitro (human dermal fibroblasts) and an in vivo complementary DNA array study in combination with protein analysis in young and old volunteers. Several genes of the collagen metabolism such as Collagen I, III and VI as well as heat shock protein 47 and matrix metalloproteinase‐1 are expressed differentially, indicating UV‐mediated effects on collagen expression, processing and degradation. In particular, Collagen I is time and age dependently reduced after a single UV exposure in human skin in vivo. Moreover, older subjects display a lower baseline level and a shorter UV‐mediated increase in hyaluronan (HA) levels. To counteract these age‐dependent changes, cultured fibroblasts were treated with a specific soy extract. This treatment resulted in increased collagen and HA synthesis. In a placebo‐controlled in vivo study, topical application of an isoflavone‐containing emulsion significantly enhanced the number of dermal papillae per area after 2 weeks. Because the flattening of the dermal‐epidermal junction is the most reproducible structural change in aged skin, this soy extract appears to rejuvenate the structure of mature skin.

Biochemical and structural changes of the dermal connective tissue substantially contribute to the phenotype of aging skin. To study connective tissue metabolism with respect to ultraviolet (UV) exposure, we performed an in vitro (human dermal fibroblasts) and an in vivo complementary DNA array study in combination with protein analysis in young and old volunteers. Several genes of the collagen metabolism such as Collagen I, III and VI as well as heat shock protein 47 and matrix metalloproteinase-1 are expressed differentially, indicating UV-mediated effects on collagen expression, processing and degradation. In particular, Collagen I is time and age dependently reduced after a single UV exposure in human skin in vivo. Moreover, older subjects display a lower baseline level and a shorter UV-mediated increase in hyaluronan (HA) levels. To counteract these age-dependent changes, cultured fibroblasts were treated with a specific soy extract. This treatment resulted in increased collagen and HA synthesis. In a placebo-controlled in vivo study, topical application of an isoflavone-containing emulsion significantly enhanced the number of dermal papillae per area after 2 weeks. Because the flattening of the dermal-epidermal junction is the most reproducible structural change in aged skin, this soy extract appears to rejuvenate the structure of mature skin.