<i>In vitro</i> and <i>in vivo</i> comparative study of cosmetic ingredients Coffee silverskin and hyaluronic acid (2016)

Facial wrinkles are one of the major features of ageing. Traditionally, hyaluronic acid (HA) is used as a potent antiwrinkle compound. HyaCare® Filler CL (Evonik Industries AG, Essen, Germany) is a new anti-ageing ingredient with a cross-linked polysaccharide made from fermentation-derived HA, contributing to the reduction in facial fine lines and wrinkles as well as increasing skin elasticity and hydration 1. Recently, the same purposes were made for caffeine. Extracts from two species of coffee directly combat UV damage improving strength, resilience and elasticity of facial skin 2. Coffea arabica seed oil significantly improves collagen and elastin production, while Coffea robusta has a high concentration of chlorogenic acid (which reduces redness) and caffeine 2. A new tendency in cosmetic formulations is the use of ingredients obtained from food by-products discarded as waste, answering to sustainability concerns 3-7. Coffee silverskin (CS) is a coffee roasting by-product with no commercial value. According to the International Coffee Organization (ICO), in 2014, the world coffee production has been around 141 620 million bags of 60 kg, which means that about 3 823 740 kg of these wastes were produced. Recent studies reveal its antioxidant potential, caffeine content and low cytotoxicity 6. Rodrigues et al. evaluated the CS skin and ocular irritation potential, using reconstructed human epidermis, EpiSkin™ (SkinEthics Laboratories, Lyon, France), and human corneal epithelial model, SkinEthics™ HCE (SkinEthics Laboratories, Lyon, France), respectively 7. Results demonstrated that CS is not irritant and the in vivo assay revealed that extract can be regarded as safe for topical application 7. Is CS a new antiwrinkle ingredient? Caffeine permeates the skin? Is this formulation safe? The in vitro caffeine release, hydration effect of CS and cytotoxicity of formulations were evaluated. A cream containing CS (Formulation A) was compared to an equal formulation supplemented with 1.5% of HyaCare® Filler CL (Formulation B). Clinical studies were conducted in volunteers. Biophysical techniques included visual evaluation, Corneometer® (Courage & Khazaka, Koln, Germany), Cutometer® (Courage & Khazaka, Koln, Germany), profilometry and sensorial evaluation (Data S1). Franz diffusion cells were used and pig ear skin selected as model barrier, to evaluate the caffeine permeation. Results are presented in Fig. 1. After 8 h, a very small amount of caffeine crossed the skin, respectively, about 20% of the extract content. The extract improves skin hydration after 48 h of a patch test when compared to the negative control used (P < 0.05) (Table S1). Probably, this effect is due to the well-detailed extract composition 6, 7. For keratinocyte (HaCaT) and fibroblast (HFF-1), no cytotoxicity was observed for the different concentrations tested (1, 5 and 10 mg/ml), which means that these formulations are potentially safe (Table S2). Standardized clinical photographs were taken at baseline and at 28 days using a Visioface® (Courage & Khazaka, Koln, Germany) to obtain standardized images in terms of brightness, image size and field of vision (Figure S1). The skin moisture content was measured at time 0 and after 28 days of the study. Formulation A improved from 54.74 ± 6.57 to 65.54 ± 5.67 corneometer units (CU), while Formulation B was from 55.76 ± 5.98 to 62.08 ± 9.20 CU. The hydration improvement was similar for both creams, with statistical differences regarding time 0. No statistical differences were observed between formulations A and B. The elasticity is a basic measurement for all cosmetic products that are intended to be claimed as anti-ageing. The Cutometer® parameter UF (maximum deformation during the first cycle) gives information about the firmness of the skin. Lower amplitude correlates with firmer skin. During the application period, UF decreased for formulation A, from 0.37 ± 0.09 mm to 0.35 ± 0.06 mm, and formulation B, from 0.36 ± 0.09 mm to 0.35 ± 0.13 mm. However, no significant differences (P < 0.05) were detected at time 28 days. Also, it has to be remarked critically that the interindividual differences of this absolute parameter were well pronounced. To make valuable statements on the effects influencing the viscoelasticity of the skin, relative parameter seems to be useful instead of absolute parameters. The relative Cutometer® parameter Ur/Ue stands for the neto-elasticity of the skin. The initial values were similar for both formulations. The application period of 28 days leads to an increase in Ur/Ue from 0.50 ± 0.13 mm to 0.57 ± 0.04 mm for Formulation A and from 0.48 ± 0.15 mm to 0.58 ± 0.13 mm for Formulation B. Both formulations increased the neto-elasticity of the skin to a certain extent with statistically significant differences. There was no difference in effectiveness between the formulations. Regarding the Ur/Uf parameter, that allows for biological elasticity, it is also possible to observe an increase for both formulations. Formulation A presented an increase from 0.23 ± 0.04 mm to 0.26 ± 0.04 mm, while formulation B had an increase from 0.22 ± 0.05 mm to 0.26 ± 0.05. Once again, inside both formulations, it is possible to observe statistical differences at time 28 days. No statistical differences were observed between formulations A and B. The PRIMOS® (Canfield, Fairfield, New Jersey, USA) test was conducted at the corner of the eye, allowing a precise evaluation of wrinkle depth, roughness and volume of cavities. Fig. 2 is an example of a detailed skin surface analyses carried out, revealing a gradual refilling of an eye wrinkle. The analysed wrinkle depth decreased from 206 μm to 179 μm after one treatment of 28 days. However, no statistical differences were observed considering all volunteers. Between Formulation A and Formulation B, no differences were observed. The volume of the wrinkle did not change after 28 days, but a slight decrease could be observed, with no statistical differences. Regarding volume of cavities and roughness, it is possible to observe a slight decrease for both formulations, but no statistical differences were observed. In a general way, all volunteers appreciated both formulations (Data S3). This is the first report describing the successful use of CS as cosmetic active ingredient. CS was shown to be an effective ingredient, with similar results to HA, in the improvement of skin hydration and firmness. The authors acknowledge all volunteers. FR is thankful to Foundation for Science and Technology (Portugal) for her Ph.D. grant (SFRH/BDE/51385/2011). FR designed, performed and analysed the research. FR wrote the paper. RM, MF, HA and BO contributed essential reagents or tools. The authors declare no conflict of interests. Data S1. Materials and Methods. Data S2. References. Figure S1. Illustrative images obtained with the digital photography imaging system Visioface® at time 0 and after 28 days. Table S1. Hydration variation from basal values of negative control (NC) and CS extract (CS) at time 0 and 2 h after patch removal following a 48 h occlusion period. Table S2. Effect on the metabolic activity of HaCaT and HFF-1 cells after the exposure to Formulation A and B at different concentrations, measured by the MTS assay. Values are expressed as mean ± SD (n = 6). Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.