HAIR LIPID COMPOSITION 7 HCs, SQ, WEs, TGs, and FAs in the extractable lipids were determined by HPTLC­ densitometry according to the conventional method (16, 1 7). A representative chromato­ gram is shown in Figure 3. MEA in the integral lipids was determined by HPLC following its derivatization with ADAM according to a previously reported method (6), and a representative chromatogram is shown in Figure 4. CH in the lipids was deter­ mined by GC, based on a previously reported method (7), and a representative chro­ matogram is depicted in Figure S. Sphingoids generated by hydrolysis of CE Rs in the lipids were determined by HPLC following their derivatization with OP A (Figure 6). The major and minor sphingoids were identified as erythro (C 18 -)dihydrosphingosine (peak C in Figure 6), and (C 18 -)sphingosine (peak A in Figure 6) by comparison with authentic standards. Peak D in Figure 6 was identified as erythro-C 20 -dihydro­ sphingosine based upon comparison with GC/MS data for acetylated and silylated sphin- 12 cm...-----------....----. HCs 9cm I SQ WEs I TGs 6cm I FAs 3cm 0cm A B C D E F Figure 3. A HPTLC chromatogram of lipid references and extractable lipids. Lane A: tetracosane. Lane B: squalene. Lane C: cetyl palmitate. Lane D: tripalmitin. Lane E: palmitic acid. Lane F: extractable lipids.

8 JOURNAL OF COSMETIC SCIENCE A B C D •· · ··· ·••1••·•• 11 ••1• •·····••1 11 ••···••1 1••1111•1 1 10 20 30 40 50 Time/min Figure 4. A HPLC chromatogram of fatty acid-ADAM derivatives in integral lipids. A: palmitic acid. B: stearic acid. C: MEA. D: tricosanoic acid as an internal standard. goids (data not shown). The absence of peaks at ca. 11 min in Figure 6 indicates that human hair contains little CERs with phytosphingosine. Both CH and CERs were calculated as the sum of the extractable lipids and the integral ones, since it is unclear whether they should be chemically distinguished from each other or not in the case of CH and CERs different from MEA, which is clear in its chemical state (6). STATISTICAL ANALYSIS OF THE LEVELS OF THE HAIR LIPIDS The variation of the hair lipids among individuals is shown in Table I. An average of the level of each lipid was in the order of (FAs) (WEs) (HCs)(CH) (SQ) (TGs) (MEA) � (CERs). The major hair lipids can be assigned as FAs and WEs since their sum accounted for more than 85% of the total lipids (average 23.5 mg/g hair). The percent­ age of coefficient of variation was in the order of (TGs) (SQ) (WEs) � (FAs) ===:= (HC) (total lipid) (CH) (CERs) (MEA), thus indicating that their levels of TGs, SQ, WEs, FAs, and HCs among individuals fluctuate more than those of the total lipids. Relationships between the levels of each lipid were analyzed (Table II). There was a significant positive correlation (p 0.01) among the levels of SQ, WEs, and FAs, one of which is shown in Figure 7 A. A significant positive correlation (p 0.01) between the levels of CH and CERs was also observed (Figure 7B). Further, there was a significant negative correlation between the levels of SQ and CH (p 0.01), SQ and CERs (p 0.05), WEs and CH (p 0.01), WEs and CERs (p 0.01), TGs and CH (p 0.01), TGs and CERs (p 0.05), FAs and CH (p 0.01), and FAs and CERs (p 0.01) (Table II). A representative negative correlation between WEs and CH is shown in Figure 7C. While HCs were weakly correlated only with CERs (p 0.05), MEA exhibited no significant correlation with any other lipids.