PREDICTING ABSORPTION OF FRAGRANCE CHEMICALS THROUGH HUMAN SKIN

Potts and Guy fitted an equation to the experimental permeation coeffi cients (Kp) of a variety of molecular structures through human skin (1 ). This equation was based on molecular weight (MW) and the octanol-wa ter partition coefficient (log P). In the endeavor to identify a mathe matical model predictive of the mostly unexplored skin penetration of fragrance chemicals, the Ports-Guy equation was tested here by correla ting the published, measured Kp for 20 such compounds with predicted K p values. The data, covering a broad range of structures, are well des cribed by that model (r(2) = 0.86, p < 0.001). Also, calculated octano l-water partition coefficients, an alternative in case of missing meas ured values, appear well founded when analyzed statistically: comparis on of 33 measured partition values with the calculated log Ps show nea r-perfect correlation for the intermediate lipophilicity range typical of fragrance chemicals (0.5 < log P < 3.5; r(2) = 0.97, p < 0.001). T he Ports-Guy relation thereby recommends itself as a simple and reliab le method for the quantitative evaluation of human skin absorption pot ential of small-molecular-weight nonelectrolytes, and of fragrance che micals, in particular where such data are largely missing.