EBT3 Gafchromic® film as a new substrate for in vitro evaluation of sun protection factor.

There exist different methods for the determination of sun protection factor (SPF) values for sunscreens. We aimed to develop a new in vitro method using EBT3 Gafchromic® film as a substrate. The colour of EBT3 Gafchromic® film changes when exposed to UV light. Films were covered by sunscreen preparations of different SPF values ranging from 0 to 50. Uncovered and covered films were exposed to different solar light energies and their colour change was compared. Absorbance spectra of films was measured at 633 nm using a UV-VIS spectrophotometer apparatus. The colour of the film darkens when ultraviolet energy increases, which means that absorbance increases with exposure time. However, when films are covered by sunscreens, the colour change is less visible and the absorbance significantly decreases with increasing SPF value. There is a linear correlation between the absorbance of EBT3 Gafchromic® film and SPF value of sunscreens covering the film. Statistical analysis demonstrated that the SPF value of a sunscreen can be predicted using EBT3 Gafchromic® film as a substrate. This is the first report of an in vitro method based on colour change of a substrate which takes into consideration exposure time, and relates more closely to conditions of real-life. Based on these parameters, this is a reliable in vitro method for SPF testing.

Assessment of the skin barrier function in the reconstructed human epidermis using a multimodal approach at molecular, tissue and functional levels.

Reconstructed human epidermis models are used as epidermis alternatives in skin research studies. It is necessary to provide molecular and functional characterization in order to assess these models. Our aim is to establish a link between the barrier function and the structure and composition of the stratum corneum using several complementary techniques. The following three studies were performed on reconstructed human epidermis during the keratinocyte differentiation process: (i) caffeine percutaneous penetration kinetics, (ii) epidermis thickness measurement, stratum corneum formation and lipid organization by Raman microspectroscopy and (iii) lipid composition evolution by liquid chromatography coupled to high-resolution mass spectrometry. The results demonstrated that the caffeine penetration decreased along the differentiation process. Raman in-depth images demonstrated an increase in stratum corneum and RHE thickness accompanied by the evolution of lipid organization. Lipid analysis showed an increase of the ceramide amount and an inverse relationship between ceramide and its precursor levels during the differentiation process. Different behaviors between several ceramide subclasses are highlighted and they relied on the corresponding differentiation stages. The generation of the most important ceramides for the barrier function is closely followed. A period shift between lipid generation and their organization was found. Our analytical data allowed identifying the following 3 groups of maturation days: before day 15, between days 15 and 19, and after day 19. The chemical and physiological states of the barrier function for each group are described thanks to a multimodal approach.

Skin lightening effect of natural extracts coming from Senegal botanical biodiversity.

BACKGROUND: Skin depigmentation is increasingly oriented toward plant extracts because of harmfulness of depigmenting active ingredients used in cosmetics and dermatology. Reconstructed human pigmented epidermis (RHPE) is the closest in vitro model to human skin and offers the possibility to test the global depigmenting effect of a plant extract. These co-cultures of keratinocytes and melanocytes are the most advanced and newest models for testing depigmentation, and until now very few studies have been done with these cultures. We investigated the cytotoxicity and the inhibitory effect on tyrosinase and melanogenesis of four extracts from Combretum micranthum (G. Don) leaves, Anacardium occidentale (L.) fruits, Moringa oleifera (Lam.) seeds, and Adansonia digitata (L.) seeds. METHODS: The vegetal extracts were obtained by ultrasound-assisted extraction and the vegetal oils by maceration. Anti-tyrosinase properties of two aqueous extracts were evaluated. Then, the cytotoxicity and depigmenting effects of these plant extracts were tested in vitro with RHPE model delivered by SkinEthic® . RESULTS: Antityrosinase activities were found to be 84.58% and 31.02% for C. micranthum and A. occidentale, respectively. All extracts, except A. occidentale, showed to be nontoxic. C. micranthum, M. oleifera, A. digitata, and mixture of M. oleifera and A. digitata extracts have shown, for the first time, an in vitro depigmenting activity equivalent or even more important than kojic acid. CONCLUSIONS: These natural extracts coming from Senegal botanical biodiversity could be used in cosmetic and dermatology as alternative agents to achieve skin depigmentation. Further study should be focused on the mechanism of action of these plant extracts.

Origanum essential oils reduce the level of melanin in B16-F1 melanocytes.

BACKGROUND: Hyperpigmentation disorders are considered signs of skin aging and are aesthetically unpleasant. Most active ingredients used against hyperpigmentation disorders predominantly target tyrosinase activity. OBJECTIVES: To study the effect of two Origanum essential oils on the melanogenic activity of B16-F1 murine melanocytes. The main component of these oils, carvacrol, was also investigated and a model for anti-melanogenic activity is proposed. MATERIALS AND METHODS: B16-F1 melanocytes were exposed to different concentrations of essential oils and carvacrol. The level of tyrosinase and melanin was determined using spectrophotometric measurements. RESULTS: Essential oils of Origanum syriacum and Origanum ehrenbergii led to a significant 14% and 17% reduction in melanin level at 40 µg mL-1, respectively. However, neither demonstrated a significant effect on the level of intracellular tyrosinase. The same effects were found for carvacrol which led to a 30% reduction in melanin at 45 µg mL-1. CONCLUSION: Our results indicate that the oils studied are anti-melanogenic. We propose a mechanism, similar to that for hydroquinone, whereby carvacrol functions as a competitive inhibitor of tyrosinase, thus inhibiting oxidation of tyrosine and causing a deregulation of melanogenesis.

Phytochemical screening and antityrosinase activity of carvacrol, thymoquinone, and four essential oils of Lebanese plants.

OBJECTIVE: In our study, we aim to explore the ability of four essential oils (EO) of Lebanese plants to inhibit the tyrosinase activity and to correlate their efficiency level to their phytochemical compositions. METHODS: The EO have been extracted by hydrodistillation using a Clevenger apparatus and have been studied by GC-MS analysis. Active compounds of Origanum species were identified and antityrosinase activities of EO and active molecules (carvacrol and thymoquinone) have been tested in tubo. RESULTS: Antityrosinase activities were obtained as follows: EO of Origanum syriacum (80.41% ± 2.00%), EO of Origanum ehrenbergii (45.33% ± 2.20%), EO of Salvia fruticosa (14.62% ± 2.30%), EO of Calamintha origanifolia (16.51% ± 5.80%), Carvacrol (56.55% ± 3.10%), and Thymoquinone (19.49% ± 1.50%). CONCLUSION: Origanum essential oils resulted in the highest antityrosinase activity due to their high content in carvacrol. However, when present together with carvacrol, thymoquinone decreases the efficiency of carvacrol, which is the case of O. ehrenbergii essential oil. Thus, for improved antityrosinase activity, O. syriacum and O. ehrenbergii should be harvested during flowering stage where carvacrol is present at its highest dosage and thymoquinone at its lowest.