EMOLLIENT ACTION OF KUKUI NUT OIL 241 FATTY ACID ANALYSIS Lipid saponification, methylation, and gas chromatographic quantification of fatty acid methyl esters were done as described previously (4), except for skin stripping samples, which were concentrated with a nitrogen stream just before running on the gas chro- matograph. AOAC methods were used to determine peroxide values. STABILITY In room temperature stability studies, kukui oil was held in glass vials on the windowsill (approx. 28øC). Some samples were flushed with nitrogen and sealed, and others were left open to the atmosphere with glass wool plugs keeping debris out of the vials. Some samples contained antioxidants (a mixture of vitamins C, E, and A), and others did not. In these stability studies, each data point represents an average of triplicate analyses. Accelerated rancidity tests were done with samples held in vials in a dry incubator at 60øC on the laboratory bench. SKIN PENETRATION Skin strippings were done following the approach of Brod et al. (5). Samples (none, 20 Ixl coconut oil, 20 •1 kukui oil, or 50 mg of kukui lotion) were applied to 25-cm 2 sections of skin on the shins of test subjects. Samples were rubbed into the skin gently with a test tube. After one and a half hours, Blenderm © tapes were applied to each of the sections with a light touch and removed after about one minute. A total of five consecutive strippings were done for each sample. No measurements were taken of the depths of skin removed with each stripping. However, we were conscious of possible inconsistency and attempted to remove equal amounts of skin in each stripping. There were no apparent differences in stripped skin to which different treatments were applied. In no case did the skin seem "tender" or "raw," as was the case in a preliminary study when tapes were applied vigorously. Oils were extracted from individual tapes with hexane as described by Brod et al. (5) and were analyzed for fatty acids as described above. A follow-up test was done at half- loading rates (10 •1 coconut oil and 10 •1 kukui oil per 25-cm 2 section of skin). STATISTICS The Student's t-test was used. RESULTS STABILITY The linolenate levels in kukui oil were taken as indicative of rancidity because linolenate is the most unstable fatty acid in kukui oil. Figure 1 is a room-temperature stability test. The closed triangles represent a control reaction with kukui oil containing no antioxidants and exposed to air. The data show that kukui oil rapidly became rancid

242 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 120 lOO 8o 6o 4o 2o -- _ - / / - O 1 2 3 4 5 6 7 Months at room temp. Figure 1. Stability of kukui nut oil at room temperature. Percentages of linolenate (C18:3n-3) remaining in kukui oil aoeter incubation. Closed triangles, in air, no antioxidants open triangles, in air open squares, under N2 closed squares, under N2, no antioxidants. after three months. Antioxidants protected against rancidity induced by exposure to air (open triangles). Stability tests done under a nitrogen atmosphere were considered to be models for kukui oil stability during shipping to a potential customer. The data (open squares) suggest that kukui oil remained stable for three to five months. Figure 2 is an elevated-temperature stability test. The data in Figure 2 suggest that 90% of the kukui oil remained non-rancid for about 17 days at 60øC. This contrasts with the results of the peroxide value test. Kukui oil without antioxidants exposed to air had peroxide values of 44 -+ 2.3 after 23/4 days exposure to 60øC and 133 -+ 63 after 17 days. With antioxidants and exposure to air, kukui oil had peroxide values of 7.0 -+ 0.3 and 41 -+ 6.3 at 23/4 and 17 days, respectively. Under a nitrogen atmosphere in the presence of antioxidants, peroxide values were 4.3 -+ 0.9 and 31 -+ 4.6 at the same incubation times. A repeat of the elevated-temperature test with the same batch of oil yielded indistin- guishable results using the linolenate test, while another repeat of the elevated- temperature test with a different batch of oil yielded similar but statistically different results. SKIN PENETRATION Table I is an example of a typical stripping. In the control region of the skin (no oil applied), lipid is concentrated in the top layers of skin. There was less and less oil as one