JOURNAL OF COSMETIC SCIENCE 60 corneum is defective, by aiding in the restoration of barrier function, while increasing skin hydration, elasticity, and fi rmness. INTRODUCTION Skin surface lipids (SSLs) are primarily composed of fatty acids (FAs), triglycerides, cholesterol, cholesteryl esters, wax esters, and squalene (1). The SSLs are either of sebaceous origin (i.e., sebum) (approximately 90%) or epidermal origin (approximately 10%), and the fraction of any one component varies based on body location (i.e., whether the location is rich in sebaceous glands) (2). Wax esters, squalene, glycerides, free fatty acids (FFAs), and cholesteryl esters are primarily derived from sebaceous glands (3). Cholesterol, FFA, and ceramides mainly originate in the epidermis along with small amounts of cholesteryl es- ters, and glycerides (3). SSLs greatly affect the skin physiology and are thought to be in- volved in skin processes such as thermoregulation (4), bacterial colonization (5), and barrier function and maintenance (6). Although much research has been done to quantify the total content and various SSL components, there is still much debate as to the best method of noninvasive collection and analytical technique, as well as whether or not outside factors such as race, gender, and age affect the collective quantity or the percent composition of each SSL component. Previously explored methods of collection include (i) solvent extraction (2), (ii) Sebutape® (CuDerm Corporation, Dallas, TX) (7), and (iii) cigarette paper (8). Additionally, samples have been analyzed using various methods such as (i) thin layer chromatography (8), (ii) infrared spectroscopy (9), (iii) high-temperature gas chromatography and mass spectrom- etry (GC-MS) (10), (iv) nuclear magnetic resonance spectroscopy (11), (v) high-performance liquid chromatography (HPLC) and MS (12), or (vi) combinations of analytical tech- niques (13). This current body of research used the cigarette paper collection method in conjunction with GC-MS analysis to determine the percent composition of each of the SSL compo- nents. On the basis of the research conducted by Shetage et al. (14), the cigarette paper method produces the most consistent data. Analysis by GC-MS allows optimal separation and identifi cation of desired lipid components and constituents that cannot be achieved without a combination of chromatographic and mass spectral analysis. An all-female population was used to evaluate variance between highly similar individuals. The age 22 was chosen because sebum excretion rates are at a maximum within the 16- to 40-year age range (15), and remain steady through the 20s and 30s (16). The composition of 22-year-old healthy female SSLs was then used to generate a botani- cally sourced SSL mimetic to determine the physiological effects when an SSL mimetic is applied to the skin topically. Moisturizers are often used for treatment of dry skin condi- tions, whether it is in conjunction with a drug for disease states like atopic dermatitis or psoriasis, daily use for self-perceived dry skin due to age or climate, or as a protectant in the workplace due to frequent contact with chemical agents (17). Moisturizers have both short- and long-term hydration and barrier function effects on the skin, and these effects are highly dependent upon the physicochemical properties of the moisturizer, e.g., pH, occlusivity, and type of ingredients used (17,18). The effi cacy portion of this research primarily focused on the short- and long-term functions of skin hydration and skin bar- rier function and maintenance when an SSL mimetic is applied topically to the skin.

BOTANICALLY DERIVED SKIN SURFACE LIPID MIMETIC 61 MATERIALS AND METHODS SUBJECTS AND SAMPLE COLLECTION The study, which was performed in Chandler, AZ, was approved by the Argus Indepen- dent Review Board (Tucson, AZ) prior to beginning any study procedures. Written in- formed consent was obtained from all subjects. Fifty-nine healthy, 22-year-old females were selected according to the following criteria: no active skin diseases on the face (e.g., acne, psoriasis, atopic dermatitis, eczema, rosacea, and skin cancer), no immunological disorders, and not pregnant or nursing. The subjects consisted of fi fty Caucasian, three African American, two Asian, and four mixed race persons. Solvent-washed cigarette rice papers (Rizla UK, Ltd, Pontypridd, United Kingdom) were used as lipid-free absorbent papers. Among the papers tested, it was found that adhesive- free rice paper contained the least amount of contaminants, particularly lipids. This is often an issue when using adhesive-containing collection methods such as Sebutape (CuDerm Corporation, Dallas, TX). Approximately 50 papers were washed at a time with 250 ml HPLC-grade diethyl ether in an ultrasonic water bath for 15 min at room temperature. After extraction, the cigarette rice papers were removed from the solvent and dried in a rotary evaporator. The papers were stored in polyethylene jars until further use on subjects. Subjects were instructed to wash their faces approximately 12 h before sampling using Cetaphil® Gentle Skin Cleanser (Galderma, Fort Worth, TX), supplied by Floratech (Chandler, AZ), to remove dirt and oil from the facial skin. After this 12-h period, sub- jects reported to the testing facility where they acclimated in a controlled environment [20°–22°C, 50% relative humidity (RH)]. Noninvasive sampling of SSLs from the fore- head of each subject was then conducted over the course of 2 h in the following manner. Two sheets of lipid-free absorbent paper were placed on top of one another in the center of the forehead and held in position for 30 min. The paper was then removed, and placed in a sealed container for extraction. The lipid absorption step was then repeated, consecu- tively, three additional times. EXTRACTION AND SAMPLE ANALYSIS Each subject’s collection papers were extracted twice with 25 ml HPLC-grade diethyl ether (Honeywell Burdick and Jackson, Muskegon, MI) in an ultrasonic water bath for 10 min. The collection papers were removed from the extraction fl ask, and the diethyl ether was evaporated under a gentle stream of nitrogen at 70°C on a hot plate until dry. After drying, the samples were weighed and diluted with an appropriate amount of isooctane (EMD Millipore, Billerica, MA) to obtain a uniform concentration range for the series of samples, approximately 0.5–0.7 μg/μl. The instrument consisted of an Agilent 6890 GC with a programmable cool on-column injector coupled to an Agilent 5973N with turbo pump (Santa Clara, CA). The in- strumental analysis methods were developed using strategies referenced from Michael- Jubeli et al. (19). Software control and data analysis were accomplished with Agilent MSD Chemstation D.02.00.237, NIST 11 (Gaithersburg, MD), and AMDIS v2.70 (Gaithersburg, MD).