J. Cosmet. Sci., 71, 367–375 (November/December 2020) 367 Detection and Analysis of Ceramide in Skin and Blood in a Healthy Chinese Population CONG XIN, YAOCHI WANG, YULING CHANG, BO ZHANG, and SEN YANG , Institute of Dermatology and Department of Dermatology, the First Affi liated Hospital, Anhui Medical University, Hefei, China (C.X., S.Y.), Clinic Medical College of Anhui Medical University, Hefei, China (Y.W.), Department of Dermatology, the People’s Hospital of Zhengzhou, Zhengzhou, China (Y.C.), Wuxi Branch of Zhongda Hospital, Southeast University, Wuxi, China (S.C.), Department of Oncology, the Second Affi liated Hospital, Anhui Medical University, Hefei, China (B.Z.) Accepted for publication April 12, 2020. Synopsis To explore the signifi cance of ceramide in the skin barrier and its potential utility within the cosmetics industry, an accurate and high-speed method was used to detect the types of ceramides in the skin and blood of a healthy Chinese population. Forearm cortical skin stratum corneum samples were obtained from four healthy subjects using a noninvasive method. In addition, these subjects were collected intravenously to obtain blood samples. Ceramides were detected in skin and blood samples using high-performance liquid chromatography coupled with specialized high-resolution Fourier Transform mass spectrometry machine. Data were analyzed using full-fl ow lipid analysis software. Peaks representing ceramides were detected in all skin samples and some blood samples. The results show that ceramides in skin are predominantly long-chain ceramides, but mainly short-chain in the blood. Simple and fast qualitative and quantitative analysis of ceramide in the skin and blood provides a basis for the precise addition of ceramide in future skin care products and the metabolic regulation and prevention of various diseases. INTRODUCTION The stratum corneum (SC) of the epidermis is the main barrier to prevent the entry of external substances into the human body and reduce trans-epidermal water loss (1). Intercellular lipids mainly include ceramide (about 50%), cholesterol (about 25%), free fatty acids (about 15%), and a small amount of phospholipids. Ceramides combined with cornifi ed envelope have a physiological function in corneocyte fl exibility (2). Ceramide is closely related to many diseases. Decreased ceramide content in the SC will destroy the skin barrier, including atopic dermatitis (AD), psoriasis, and other diseases (3). Address all correspondence to Sen Yang at yang2004sen@163.com and Bo Zhang at alvinbo@163.com . Cong Xin and Yaochi Wang contributed equally to this work.

JOURNAL OF COSMETIC SCIENCE 368 Ceramides can be used as a moisturizer to treat dry skin. Many kinds of ceramides can be used synergistically to improve skin barrier function (4). Ceramides can also reduce the severity of skin diseases, reduce pain, improve the effi cacy of other drugs, reduce adverse reactions to drugs, accelerate the recovery of diseases, and improve quality of life (5). Ceramides have been used in topical formulations of AD (6). Ceramides can also reduce the reactivity to environmental pollution and skin sensitivity (7). Ceramide in the blood is used as a biomarker for predicting cardiovascular diseases (8) and pulmonary cystic fi brosis (9) and other diseases. Increase of ceramide contents in the blood may also be related to the risk of Alzheimer’s disease and can predict cognitive impairment (10). Therefore, determi- nation of the ceramide content qualitatively and quantitatively is very important for assess- ing skin condition and occurrence and development of various diseases. Busman (11) measured intracellular ceramide species using high-performance liquid chroma- tography (HPLC) coupled to atmospheric pressure-ionization mass spectrometry (MS). Zhixin (12) extracted human epidermis SC using tape stripping, and then quantifi ed ceramides using normal-phase liquid chromatography combined with dynamic multi-reaction monitoring MS. Twelve ceramide subclasses were found, including CER[NDS], CER[NS], CER[NP], CER[NH], CER[ADS], CER[AS], CER[AP], CER[AH], CER[EODS], CER[EOS], CER[EOP], and CER[EOH]. Here, we identifi ed the ceramide kinds and measured its content in skin and blood samples using HPLC and high-resolution MS and then analyzed them. The difference in ceramide in different tissues has not been detected by using precise methods. The high-throughput mass spectrometer has detected ceramide, and the detection result has high accuracy and the detection speed is very fast. MATERIALS AND METHODS SUBJECTS Subject inclusion criteria: healthy Chinese volunteers (18–65 y old, no gender requirements), no history of skin disease, no skin care moisturizers or other topical preparations used within 1 mo before the study, no allergic reaction to cyanoacrylate, no history of phototherapy in a year, no history of drug use in the past month, and no history of chronic wasting disease. Subject exclusion criteria: The trial does not include juvenile children, pregnant women, lactating women, and patients who use hormone replacement therapy or immunotherapy. The study was approved by the Research Ethics Committee of the Anhui Medical University and conformed to the Declaration of Helsinki. After being completely notifi ed of the proce- dures, written informed consent was obtained from all participants. Four volunteers partici- pated in our study, and we collected and processed their blood samples and skin SC samples. MATERIALS AND LIPID STANDARDS Chemicals. Methanol and chloroform were obtained from Sinopharm Group Chemical Reagent Company Limited, ultrapure water was obtained by Thermo ultrapure water machine, and cyanoacrylate glue was purchased from Deli Group Company Limited (Ningbo, China).