SKIN PENETRATION ENHANCING ACTION OF CIS-UNSATURATED FATTY-ACIDS WITHOMEGA-9, AND OMEGA-12-CHAIN LENGTHS

The skin penetrative action of high purity cis-omega-12-octadecenoic a cid (petroselinic acid, HP-PSA) on rat skin was compared with that of high purity cis-omega-9-octadecenoic acid (oleic acid, HP-OA), followi ng treatment of rat int-ad. skin surface with either 0.05 M HP-PSA or HP-OA in propylene glycol (PG), using Fourier transform/attenuated tot al reflection (FT-IR/ATR) analysis. Roth HP-PSA and HP-OA disordered t he lipid structures of the stratum corneum region to a similar extent. Removal of the extractable Lipids of the stratum corneum region was m arked with HP-PSA/PG but was very slight upon HP-OA/PG treatment, The spectra of the amide ii region which originated from proteins suggests that HP-PSA/PG mole rapidly disordered the protein structures of both the stratum corneum and the dermis than HP-OA/PG. However, the extent of disordering of the protein structures was presumed to be similar b etween these two skin penetration enhancers at the maximum level, Enha ncement of PG flux in the dermis showed strong positive correlation wi th the degree of dermis-disordering action of HP-PSA/PG and HP-OA/PG. These results demonstrate that HP-PSA, which has a double bond at an e ven numbered position (omega-12), more rapidly affects the perturbatio n of the structures of both the stratum corneum and the dermis than HP -OA, which has the double bond at an odd numbered position (omega-9), Differences in the physicochemical properties of HP-PSA and HP-OA whic h originate from differences in the double bond position most likely d etermine the efficacy of these compounds as skin penetration enhancers .