EMULGEL FORMULATION AND IN VITRO AND IN VIVO ASSESSMENT 7 2. In the stress–st r ain mode, the deformation of the skin (in millimeters) is showed as a function of the vacuum (in millibar). IN VIVO STUDY Study design. The d uration of th is observational crossover study was two weeks. It was approved by the Institutional Review Board at An-Najah National University, Palestine. The primary objective was to assess the organoleptic properties of emulgel such as odor, feel, smoothness, emollience, cooling effect, and skin moisturization. A blank emulgel formulation was used which lacks the LG essential oil. Volunteers. A total of 50 male and female volunteers older than 20 years with normal or dry skin were enrolled in the study. Exclusion criteria were subjects characterized as oily or sensitive skin and subjects who were using other moisturizing creams or other cosmetics. Application and ass essment. All participants w ere divided into two groups. In the fi rst week, one group was asked to apply LG emulgel formulation and the other group was asked to apply the blank emulgel formulation on their hands. Each group was asked to rate the results from 1 to 5 (1: the least and 5: the best) by fi lling a specifi c questionnaire. In the second week after a 3-days washout period, the two groups were switched to com- plete the assessment of the emulgel formulations. The results were recorded and analyzed by using a paired sample T-test. RESULTS AND DISCUSS ION YIELDS OF DIFFERENT LG PLANTS The quality control of herbal or plant drug products should start with its raw material. Specifi c information on the used plants should include agricultural practices such as growing, harvesting time, collection processing, geographic area, and storage conditions (26). Accordingly, the us ed LG was collected from the north area of West Bank, Palestine. Two sources (cultivated and wild) were evaluated for 3 mo to fi nd the best yield. The yield of LG was different according to their type and their harvesting time. As shown in Table IV and Figure 2, wild LG showed the highest yield, and the suitable harvest time was May for both cultivated and wild herbs. This may be because of the maturation of the oily glands of the grass (10). Table IV Percentage Yield of LG Essential Oil from C. citratus Leaves Yield (%) Harvesting time (month) Wild March April May 0.0 0.73 1.12 Cultivated 0.0 0.0344 0.7

JOURNAL OF COSMETIC SCIENCE 8 IN VITRO ASSESSMENT OF EMULGEL The pH of the obtai ned formulation containing wild LG oil remained constant after the cycles of freeze and thaws which were conducted using two different temperatures as summarized in Table V. The centrifugation technique is usually used to study the long-term physical stability of a semisolid pharmaceutical or formulation (27). Our emulgel retained the consistency and homogeneity even after 1 h of centrifugation at 3,000 rpm, and no phase separation was detected. In addition, the micrographic observations before and after accelerated stability tests showed that neither change in the general appearance of the micelles nor inversion was observed. The effi cacy of topical product depends on the spreading pattern of the semisolid product to deliver a standard dose. Accordingly, the consistency of such a product may en- sure that a suitable dose is applied to the target site. In fact, a very thin layer or the reduced dose may not deliver the desired effect, although a thick layer may result in an excessive dose which may lead to undesirable side effects or even lower consumer compliance. Accordingly, the spreadability of the formulation is important to ensure a consistent pattern of the application. In this study, the calculated spreading value was 76.5 g/cm, which refl ects the excellent spreadability value. This value is suitable for emulgel formulation as compared with the previous study (22). Also, the viscosity of the emulgel was measured at Table V pH Values of LG Emulgel Formulations Before stability After F/T (25°C) After F/T (40°C) 5.96 6.01 6.04 Figure 2. Percentage yield of LG essential oil versus harvesting time.