j. Cosmet. Sci., 59, 481--496 (November/December 2008) Changes in hair properties by Eucalyptus extract AKIRA MAMADA, MARIKO ISHIHAMA, REIKO FUKUDA, and SHIGETO INOUE, Kao Corporation, Beauty Research Center, 2-1-3 Bunka Sumida, Tokyo 131-8501 (A.M., M.I., R.F.), and Kao Corporation, Analytical Science Research Laboratories, 1334 Minato Wakayama, Wakayama 640-8580 (S.l.),Japan. Accepted for publication May 28, 2008. Synopsis A long-term usage investigation of a scalp lotion containing Eucalyptus extract, which increases the amount of ceramide in the skin, was carried out to explore the change in physical properties of the hair fiber. Half-head or whole-head usage studies of a scalp lotion with Eucalyptus extract were carried out for the following groups: Japanese female, Japanese senior female, Japanese male, and Caucasian female panelists. As a result, the improvement in hair luster and bounce in the root part of the hair were recognized by the panelists after the long-term application of the scalp lotion with Eucalyptus extract. Measurement of hair gloss intensity and bending stress at the root suggests that this improvement is based on changes in these physical properties. These results indicate that the recognition of panelists is based on an actual change in the hair fiber properties. The efficacy of Eucalyptus extract is expressed regardless of race, age, or gender, since similar results were confirmed in all panelist groups. In order to investigate the cause of these phenomena, we measured the elasticity (Young's modulus) of the new-growth part of the cortex in Eucalyptus extract-treated hair and placebo hair by the nano-indentation method of atomic force microscopy (AFM). These results suggest that the Young's modulus of the new­ growth part of the cortex in Eucalyptus extract treated-hair increases in comparison with placebo hair. The IR spectra of treated samples of hair show changes that appear to confirm a decrease in the alpha-helix structure and an increase in the beta-sheet structure. INTRODUCTION Plant extracts and the essential oils extracted from plants have been widely used in Chinese medicine and aromatherapy treatments since ancient times (1). For hair care products, many plant extracts and essential oils, such as chamomile, marigold, and rose hip are added, and are important ingredients. Their effects, as found by former studies, however, are limited to a direct influence on hair fibers. It has already been reported (2) that a certain type of ceramides, which consists of long alkyl chains, has a barrier function against external stress in skin. By the application of ceramides on skin, transepidermal water loss (TEWL) decreased. This means that the barrier function of skin was improved (3). Some kinds of ceramides exist in not only the 481

482 JOURNAL OF COSMETIC SCIENCE skin but also in the hair fiber (4-6) however no one has ever found ceramides to be functional in hair. As analysis techniques have advanced remarkably in recent years, detailed analysis results on the ceramide-type substances contained in hair have been reported (7-11). Hallegot et al. (12) reported that hair fibers develop a tolerance against oxidative chemical treatments such as hair bleach or the photodamage of UV after treatment with ceramide "analogous" chemicals. We have carried out long-term (2.5-3-month) usage investigations of a scalp lotion containing Eucalyptus extract. The investigations consisted of an interview to assess the panelists' perceptions of the physical properties of hair fibers, and measurements of the bending stiffness of hair treated with the Eucalyptus scalp lotion versus a placebo. EXPERIMENT AL LOTION COMPOSITION The Eucalyptus extract was purchased from Maruzen Pharmaceuticals Co., Ltd. (Ono­ michi, Hiroshima Japan 722-0062). The scalp lotions with the Eucalyptus extract (EL), containing 0.5-3% Eucalyptus extract, 50% ethanol, and de-ionized water to balance were prepared for the usage tests. In the case of the placebo scalp lotion (PL), a mixture of 50% ethanol and 50% de-ionized water was used twice a day. The compositions are indicated as weight % . INVESTIGATED PANELIST GROUPS Group 1: Group 2: Group 3: Group 4: Japanese female Japanese female Japanese male Caucasian female USAGE TEST METHOD A (N = 11, age: 26-41) (N = 17, age: 37-53) (N = 30, age: 32-41) (N = 9, age: 22-31) In the cases of Group 1 and Group 3, the half-head examination was adopted in order to exclude the seasonal factor. The distribution of the lotions EL and PL was performed using the double-blind method, that is, the information about the area on which the EL lotion was applied was not disclosed to either the panelists or the persons analyzing hair properties until the end of the investigation. The period of usage was three months for Group 1 and 2.5 months for Group 3. USAGE TEST METHOD B In the cases of Group 2 and Group 4, the whole-head examination was adopted for three months. By this method, we can assess the total consciousness about using the lotion through the interviews.