In vitro and in vivo dermal absorption assessment of acetyl aspartic acid: a compartmental study.

OBJECTIVE: The purpose of this study was to evaluate the dermal absorption of acetyl aspartic acid (A-A-A) through an in vitro and in vivo evaluation with human skin after 6 and 24 h of topical application of a cosmetic formulation containing A-A-A at 1%. METHODS: The in vitro experiment was carried out using the Franz diffusion cells system with ex vivo human skin samples. The profile of diffusion of A-A-A was evaluated after 6 and 24 h. The in vivo experiment was performed on human volunteers following a tape-stripping protocol after 6 h of topical application. A-A-A was quantified in the main skin compartments, that is the skin surface, the stratum corneum, the skin and the receptor fluid using LC-MS analysis. RESULTS: The 24-h in vitro experiment confirmed the great penetration potential of A-A-A in all skin compartments. After 6 h of topical application, the removed tape strips from both in vitro and in vivo experiments were analysed and the profile of diffusion of A-A-A was determined, allowing also an in vitro/in vivo comparison. The diffusion profile observed on the in vitro skin penetration test is highly representative of the in vivo situation evaluated on volunteers. CONCLUSION: The combination of in vitro with in vivo data confirmed that A-A-A has the capacity to diffuse through the skin after topical application and reach the dermis as the targeted skin layer for potential anti-ageing benefits.

The use of gene arrays and corresponding connectivity mapping (Cmap) to identify novel anti-ageing ingredients.

OBJECTIVE: The need for effective 'anti-ageing' treatments, in particular for the management of photodamaged skin, prompted us to develop a novel method to identify new active ingredients. The model utilized a gene profiling study with corresponding connectivity mapping (Cmap) to identify novel anti-ageing compounds using all-trans retinoic acid (RA) as the lead compound due to its beneficial effect on photodamaged skin and skin firmness. METHOD: A vehicle-controlled clinical study including nine healthy Caucasian female volunteers aged 57 ± 7 (mean ± SEM) exhibiting photodamage on their lower outer forearms was conducted. The volunteers applied RA once daily on photodamaged skin for 7 days, and biopsies were subjected to Affymetrix gene arrays. Connectivity mapping (Cmap), examining hundreds of gene expression profiles, was run on the gene signature of RA-treated photodamaged skin to identify small bioactive compounds. RESULTS: Affymetrix gene array identified 19 genes significantly differentially expressed after application of RA. Corresponding Cmap analysis revealed six natural bioactive compounds including N-acetyl aspartic acid (A-A-A) showing similar activity to RA on the differentially expressed genes identified. CONCLUSION: Based on RA mimicking gene array activity, potential use within skincare on molecular size, safety assessment and sourcing, we identified the natural amino acid, A-A-A as a potential candidate to treat ageing skin.

Clinical evaluation of a dioic acid-based formulation on facial skin in an Indian population.

The aim of this work was to investigate the effects of 1,18-octadecen-9-dioic acid (dioic acid) and a Rumex occidentalis extract complex for their skin-lightening action in an Indian population. Prior to the clinical study, the efficacy of dioic as an inhibitor of melanogenesis was confirmed on dark-pigmented human melanocytes. As part of a 12-week vehicle-controlled clinical study, the skin-lightening effect of a test product containing 1% dioic acid, 2% of a Rumex occidentalis extract and sunscreens (SPF 15) was assessed on the facial skin of 71 Indian female volunteers. Change in skin colour was monitored by (A) Chroma Meter® measurement (L*, a*, b*) and Individual Typology Angle (ITA˚) calculation and (B) Visual grading of standardized photographs by a dermatologist. Colorimetric measurements on volunteers' cheeks showed a significant increase of L* and ITA˚ compared to baseline after 4, 8 and 12 weeks of test product application. For both L* and ITA˚ measurements, changes were significantly different than the SPF 15-containing vehicle at weeks 4 and 12. These results were confirmed by the dermatological visual grading. The overall skin-lightening action of the test product was beyond the one observed with the SPF 15 vehicle. These findings show that a dioic acid and Rumex occidentalis complex deliver a significant skin-lightening effect on facial skin in an Indian population.