J. Cosmet. Sci., 72, 1–16 (January/February 2021) 1 Formulation and In Vitro and In Vivo Assessment of Natural Emulgel Containing Lemongrass Essential Oil ABDEL NASER ZAID, NIDAL JARADAT, RAMZI SHAWAHNA, FATEMA HUSEEN, AHMAD M. EID, ALAA ATTOUN, ABEER SANDOUKA, TALAL ABED ALHADI, THARAA HILAL, and WISSAL AQTASH , Department of Pharmacy, Faculty of Medicine and Health Sciences, An-Najah National University, Nablus 0000, Palestine (A.N.Z., N.J., F.H., A.M. E., A.A., A.S., T.A.A., T.H., W.A.), Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, An-Najah National University, Nablus 0000, Palestine (R.S.) Accepted for publication August 18, 2020. Synopsis This study aimed to develop a topical emulgel formulation from olive oil and lemongrass (LG) extracts and to evaluate its in vitro and in vivo (sensorial) properties in addition to its sun protection factor (SPF) value. The primary emulsion and the gel were prepared separately, and then they were levigated together to formulate the emulgel. The produced emulgel was evaluated for its physical appearance, pH, spreadability, and stability. The SPF value of emulgel was evaluated by applying the Mansur equation. Moreover, an in vivo sensorial assessment was conducted on the emulgel through a crossover study by including 20 volunteers. The results confi rm good stability for emulgel formulations because there was no signifi cant change in the pH value, no micelle inversion, or phase separation detected. The emulgel recorded a moderate SPF value (5.5) which can be useful for daily use, especially in tanned skin subjects. Moreover, the sensorial assessment of LG and blank emulgels showed a signifi cant change in the cooling effect, odor, and smoothness and add some kind of moisture. In fact, there was a signifi cant difference in overall properties between the two formulations where the p-value was less than 0.05. It is concluded the emulgel formulation containing LG and olive oil could be benefi cial in terms of applicability and stability and can be easily formulated in pharmaceutical facilities. Besides, it would be useful for daily use because of the overall suitable properties, especially odor, feel, and SPF value. INTRODUCTION Humans generally tend to use cosmetic preparations to improve their general look and skin appearance (1). Creams and gels are the most used cosmetic formulations because they have suitable characteristics that are not usually available in other semisolid prepara- tions. These characteristics include low greasiness, suitable viscosity, skin feeling, and smoothness (2). Another important semisolid preparation which contains both gel and cream properties is emulgel. This formulation includes the incorporation of emulsion in Address all correspondence to Abdel Naser Zaid at anzaid@najah.edu.

JOURNAL OF COSMETIC SCIENCE 2 a gel base. The obtained formulation shows better properties than emulsion or gel alone. In fact, the presence of gel decreases the greasy feel of the product which may result in better consumer compliance (3). In addition, it exhibits many other properties that makes it favorable for dermatological use, including being thixotropic, emollient, nonstaining, easily removed, easily spreadable, and pleasing appearance (4). Accordingly, emulgel has emerged as one of the fabulous cosmetic and topical drug delivery systems because it delivers hydrophobic materials and has a dual release system (5–7). Several fi xed oils are light, low in viscosity, and less occlusive than mineral oils. Their carrying and penetrating properties, as well as their natural content of tocopherols, carot- enoids, and essential fatty acids, render them valuable in nutritional, pharmaceutical, and cosmetic fi elds. Volatile oils are rich in fl avors and odorous compounds, which are used as fragrances, especially in the cosmetic industries. These oils act in different ways: psycho- logical (e.g., aromatherapy), physiological (e.g., anti-infl ammatory effects), and cosmetic (e.g., preservative effects because of antibacterial or antioxidant properties). They are used in the cosmetic and perfume industries as fragrances and in skincare products to promote hormonal balance to combat the buildup of toxins and for emollience of skin (8). Accordingly, preparing natural emulgel containing functional fi xed and essential oils would be of great interest and benefi t as a skin moisturizer. Cymbopogon citratus (DC.) Stapf (family: Poaceae) as lemongrass (LG), belongs to the grass family which is culti- vated in almost all tropical and subtropical countries (9). Its essential oil content is ap- proximately 1–2% calculated on a dry basis of the grass (10). The essential oil is characterized by a very high citral level (11). (12) Moreover, LG is an edible herb that is widely used in cooking, as a herbal tea, and in traditional medicine for the treatment of hypertension and diabetes (13). In addition, it showed broad-spectrum antimicrobial activity (14). In Brazilian folk medicine, LG herbs are used as a home remedy because of its anxiolytic, hypnotic, and anticonvulsant properties (15,16). The histological analysis confi rmed that LG essential oil inhibits the skin infl ammatory response in animal models (17,18). Another study showed that LG has an important insect-repellant activity which makes it a valuable preparation for this regard (19). This study aimed to formulate and evaluate the in vitro and in vivo characteristics of natural emulgel based on LG essential oils obtained from Palestine. Accordingly, the best source of LG oil was assessed based on growing conditions (wild or cultivated) and the harvesting time. MATERIALS AND METHODS MATERIAL Olive oil and LG oil were extracted from natural local sources (West Bank/Palestine). Carbopol 934 was purchased from Sunpharm (Nablus, Palestine), and glycerin and triethanolamine (TEA) were provided by Al-Zahra’a (Nablus, Palestine). Acacia was obtained from Sigma G-9752, and amaranth was provided by Sigma-Aldrich (Darmstadt, Germany) 12056-1. PLANT MATERIAL AND EXTRACT PREPARATION Two types (cultivated and wild) of C. citratus plant leaves were collected from the north West Bank of Palestine. The leaves were harvested from March to May. A voucher specimen