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A study was designed to determine the in-vitro human skin permeation rate and distribution of 14C-radiolabelled fragrance material methyldihydrojasmonate, following application in vehicle, under non-occlusive conditions. The test material was used as 1% (w/v) solutions in ethanol, a realistic concentration according to uses concentrations in formulations applied to human skin. The study was conducted according to the FDA/ American Association of Pharmaceutical Scientists (AAPS) guideline, a guideline similar/equivalent to the OECD TG 428 “Skin Absorption: in vitro Method”. Human epidermal membranes were used and membrane integrity was assessed by measuring the permeation rate of tritiated water. Permeation of the test substance was measured over 48 hours, following which the epidermal membranes were tape stripped 10 times and the radiolabel content of the strips and remaining epidermis determined. The volatility of liquid fragrance material led to loss from the surface of the epidermal membranes. This evaporative loss was estimated by measuring the loss from PTFE (polytetrafluoroethylene) sheets for each of the three fragrance materials.

 

The human skin permeation of the test substance was moderately high. Following 48 hours exposure, 45.9 ± 3.5% of the applied dose (mean ± standard error, se) had permeated into the receptor phase. Levels of fragrance material in the 48 hour surface wipe and donor chamber wash were: 1.54 % of the applied dose for stratum corneum tape strips and 1.19 % of the applied dose for the remaining epidermis. Overall recovery fragrance material was 65.8 ± 2.8%. The evaporation of the fragrance material from PTFE (polytetrafluoroethylene) was significant and evaporative loss was identified as the main cause of the low recovery of methyldihydrojasmonate when applied to epidermal membranes for 48 hours.

 

The results of this study indicated that the percutaneous absorption level of methyldihydrojasmonate was significant. The test substance permeated the skin fairly rapidly, but the permeation subsequently plateaued somewhat as the donor phase became depleted through both evaporation and loss due to permeation.