CERAMIDE IN SKIN AND BLOOD 371 skin SC of the four volunteers. LipidSearch database is then matched with lipids that may be present in the lipid profi le. CERAMIDE MATCHI NG ANALYSIS Taking skin sam ples as an example, we detected multiple ceramides from the human SC. According to the fi rst-order peak of the sample, the possible lipid type obtained was Cer(d18:0/24:0). The lipid information of the LipidSearch database was matched and analyzed according to the secondary peak map, and the red results are the matching fragments in the database (Figure 2). Finally, the chemical formula of the lipid was C42H85NO3. The structural formula and specifi c information are shown in Figure 3. In the same way, we also determined that the chemical formula of Cer(d18:0/24:0+O) is C42H85NO4, the chemical formula of Cer(d18:1/24:0) is C42H83NO3, and the chemical formula of Cer(d18:0/pO/24:0) is C42H85NO5. Relative quanti tative analysis was performed based on the ceramide reaction peak area. Four samples of skin detected the concentration of C42H85NO3 (Table I). Because of the quality error of skin samples and individual differences, the concentration of the same ceramide is different. It is believed that C42H85NO3 is the main type of ceramide in the skin. DETECTION OF BL OOD SAMPLES Some peaks can be observed in samples of blood from four volunteers, mainly correspond- ing to short-chain ceramides, as shown in Figure 4. The lipid information of the Lipid- Search database was matched and analyzed according to the secondary peak map. Finally, the chemical formula of the lipid was C20H39NO3 and C42H85NO3. Table II lists the peak Figure 2 . According to the fi rst-order peak of the chromatographic chart, the possible lipid types obtained were matched in the LipidSearch database, and the lipid information was analyzed. The red results are the matched fragments in the database.

JOURNAL OF COSMETIC SCIENCE 372 areas of the fi rst-order extraction peaks of the major ceramides in the volunteer blood sample. In the four blood samples, C20H39NO3 and C42H85NO3 showed good and stable concentrations (Table II). Therefore, we believe that C20H39NO3 and C42H85NO3 are the main types of ceramide present in the blood. DISCUSSION The skin plays an important role in protection and defense as the fi rst physiological bar- rier of the human body (13). Lipid components play an important role in the skin barrier and cooperate to maintain the health of the epidermis. Triglycerides (TG) mainly store and provide energy, phospholipids are the main components of biofi lms to prevent water Figure 3 . According to the matching identifi cation information in the LipidSearch database, the structure and information of the corresponding compound can be found in the LIPID MAPS. Table I M a jor Long-Chain Ceramides Measured in the Epidermis Sample C42H85NO3 Area Concentration Average (ng/ml) Sample 1 13,718,882 34.25 33.63 13,254,807 32.91 13,538,412 33.73 Sample 2 11,638,420 28.22 27.59 11,503,732 27.83 11,123,588 26.72 Sample 3 17,879,947 43.09 43.06 17,690,822 42.70 18,031,713 43.40 Sample 4 8,222,066 23.34 22.78 7,765,799 22.40 7,856,601 22.59