HAIR LIPID COMPOSITION 9 A I � I • . . . - .,.J . - I 5 10 1 I 0 15 Time/min Figure 5. A GC chromatogram of cholesterol in extractable lipids. A: cholesterol. A principal component analysis (PCA) for the levels of eight lipids was performed. Factor loading, eigenvalue, and contribution obtained by the PCA are shown in Table III. The first two components accounted for 60.4% of the total variation, with 42.3% in the first component (21) and 18.1 % in the second component (22). The values in 21 increased in accordance with the increase in the levels of CH and CERs and the decrease in the levels of SQ, WEs, FAs, and TGs. The values in 22 mainly increased in concert with the increase in the level of HCs. Therefore, 21 was interpreted to imply a negative corre­ lation between one lipid consisting of SQ, WEs, FAs, and TGs and another lipid consisting of CH and CERs (Table II). 22 was also interpreted to imply a definite contribution to the level of HCs. A two-dimensional projection of the PCA, which implies a total variation for the hair lipid composition of 44 Japanese females, is shown in Figure 8. The individuals who were characterized by the lower levels of SQ, WEs, FAs, and TGs, and by the higher levels of CH and CERs, were situated at a positive value of 21 (Figure 8). On the other hand, individuals who were characterized by the higher levels of SQ, WEs, FAs, and TGs, and by the lower levels of CH and CERs, were situated at a negative value of 21 (Figure 8). Based upon Figure 8, the individuals were symbolized according to their age (Figure 9). Young individuals (ages 1-10) tended to locate at the right-hand side, and older

10 JOURNAL OF COSMETIC SCIENCE C B D A 11111111111111111111111111111111111 � m n m n m � - - N N M M Time/min Figure 6. A HPLC chromatogram of sphingoid-OPA derivatives in CERs isolated from extractable lipids. A: (C 18 -)sphingosine. B: threo-(C 18 -) dihydrosphingosine as an internal standard. C: erythro­ (C 18 -)dihydrosphingosine. D: erythro-C20-dihydrosphingosine. Table I Variation of Hair Lipids Among Individuals Statistical values HCs SQ WEs TGs FAs CH CERs MEA Total Maximum (mg/g hair) 8.9 3.5 17.1 4.6 56.2 2.8 0.49 0.47 63.7 Minimum (mg/ g hair) 0.2 0.2 0.3 0.2 2.4 0.4 0.04 0.22 5.6 Mean (mg/ g haid 2.4 0.7 4.9 0.5 15.4 1.3 0.29 0.30 23.5 Variance 1 3.7 0.9 17.7 0.9 166 0.5 0.02 0.00 231 SD (mg/ g haid 1.9 1.0 4.2 0.9 12.9 0.7 0.13 0.07 15.2 CV% 81 131 85 176 84 52 45 22 65 1 0.2 mg/g hair was calculated as = 0. Abbreviations: HCs: hydrocarbons SQ: squalene WEs: wax esters TGs: triglycerides FAs: fatty acids CH: cholesterol CERs: ceramides MEA: 18-methyl eicosanoic acid. individuals (ages 11-40) tended to distribute at the left-hand side in the PCA, showing total variation of hair lipids as shown in Figure 9. DISCUSSION Since hair lipids are gradually lost as hair fibers grow, the hair lipid composition at the distal region of hair fibers may not reflect the "precise hair lipid composition." The